RESULTS: Here we present an experimental comparison of two simplified trachea models with Grade II stenosis (70% blockage), one with smooth walls and second with cartilaginous rings. The use a unique refractive index-matching method provides unprecedented optical access and allowed us to perform non-intrusive velocity field measurements close to the wall (e.g., Particle Image Velocimetry (PIV)). Measurements were performed in a flow regime comparable to a resting breathing state (Reynolds number ReD = 3350). The cartilaginous rings induce velocity fluctuations in the downstream flow, enhancing the near-wall transport of momentum flux and thus reducing flow separation in the downstream flow. The maximum upstream velocity in the recirculation region is reduced by 38%, resulting in a much weaker recirculation zone- a direct consequence of the cartilaginous rings.

CONCLUSIONS: These results highlight the importance of the cartilaginous rings in respiratory flow studies and the mechanism to reduce flow separation in trachea stenosis.}, } @article {pmid37255166, year = {2023}, author = {Silva, MLFD and Gonçalves, SF and Haniel, J and Lucas, TC and Huebner, R}, title = {Comparative study between 1-way and 2-way coupled fluid-structure interaction in numerical simulation of aortic arch aneurysms.}, journal = {Anais da Academia Brasileira de Ciencias}, volume = {95}, number = {suppl 1}, pages = {e20210859}, doi = {10.1590/0001-3765202320210859}, pmid = {37255166}, issn = {1678-2690}, mesh = {Humans ; *Aneurysm, Aortic Arch ; Models, Cardiovascular ; *Aortic Aneurysm ; Computer Simulation ; }, abstract = {Hemodynamic forces are related to pathological variations of the cardiovascular system, and numerical simulations for fluid-structure interaction have been systematically used to analyze the behavior of blood flow and the arterial wall in aortic aneurysms. This paper proposes a comparative analysis of 1-way and 2-way coupled fluid-structure interaction for aortic arch aneurysm. The coupling models of fluid-structure interaction were conducted using 3D geometry of the thoracic aorta from computed tomography. Hyperelastic anisotropic properties were estimated for the Holzapfel arterial wall model. The rheological behavior of the blood was modeled by the Carreau-Yasuda model. The results showed that the 1-way approach tends to underestimate von Mises stress, displacement, and strain over the entire cardiac cycle, compared to the 2-way approach. In contrast, the behavior of the variables of flow field, velocity, wall shear stress, and Reynolds number when coupled by the 1-way model was overestimated at the systolic moment and tends to be equal at the diastolic moment. The quantitative differences found, especially during the systole, suggest the use of 2-way coupling in numerical simulations of aortic arch aneurysms due to the hyperelastic nature of the arterial wall, which leads to a strong iteration between the fluid and the arterial wall.}, } @article {pmid37249683, year = {2023}, author = {Deng, X and Sheng, P}, title = {Evolution of channel flow and Darcy's law beyond the critical Reynolds number.}, journal = {The European physical journal. E, Soft matter}, volume = {46}, number = {6}, pages = {37}, pmid = {37249683}, issn = {1292-895X}, support = {16303918//Research Grants Council of Hong Kong/ ; }, abstract = {For incompressible channel flow, there is a critical state, characterized by a critical Reynolds number Rec and a critical wavevector mc along the channel direction, beyond which the channel flow becomes unstable in the linear regime. In this work, we investigate the channel flow beyond the critical state and find the existence of a new fluctuating, quasi-stationary flow that comprises the laminar Poiseuille flow superposed with a counter-flow component, accompanied by vortices and anti-vortices. The net flow rate is reduced by ~ 15% from the linear, laminar regime. Our study is facilitated by the analytical solution of the linearized, incompressible, three-dimensional (3D) Navier-Stokes (NS) equation in the channel geometry, with the Navier boundary condition, alternatively denoted as the hydrodynamic modes (HMs). By using the HMs as the complete mathematical basis for expanding the velocity in the NS equation, the Rec is evaluated to 5-digit accuracy when compared to the well-known Orszag result, without invoking the standard Orr-Sommerfeld equation. Beyond Rec, the analytical solution is indispensable in offering physical insight to those features of the counter-flow component that differs from any of the pressure-driven channel flows. In particular, the counter flow is found to comprise multiple HMs, some with opposite flow direction, that can lead to a net boundary reaction force along the counter-flow direction. The latter is analyzed to be necessary for satisfying Newton's law. Experimental verification of the predictions is discussed.}, } @article {pmid37241559, year = {2023}, author = {Che, H and Xu, Q and Xu, G and Fu, X and Wang, X and He, N and Zhu, Z}, title = {Numerical Study on Characteristics of Convection and Temperature Evolution in Microchannel of Thermal Flowmeter.}, journal = {Micromachines}, volume = {14}, number = {5}, pages = {}, pmid = {37241559}, issn = {2072-666X}, support = {No. U1738119//National Natural Science Foundation of China/ ; TZYY08001//China Manned Space Engineering Application Program/ ; MT1401S//China Manned Space Engineering Application Program-Two-Phase system research Rack/ ; }, abstract = {During practical usage, thermal flowmeters have a limited range of applications. The present work investigates the factors influencing thermal flowmeter measurements and observes the effects of buoyancy convection and forced convection on the flow rate measurement sensitivity. The results show that the gravity level, inclination angle, channel height, mass flow rate, and heating power affect the flow rate measurements by influencing the flow pattern and the temperature distribution. Gravity determines the generation of convective cells, while the inclination angle affects the location of the convective cells. Channel height affects the flow pattern and temperature distribution. Higher sensitivity can be achieved with smaller mass flow rates or higher heating power. According to the combined influence of the aforementioned parameters, the present work investigates the flow transition based on the Reynolds number and the Grashof number. When the Reynolds number is below the critical value corresponding to the Grashof number, convective cells emerge and affect the accuracy of flowmeter measurements. The research on influencing factors and flow transition presented in this paper has potential implications for the design and manufacture of thermal flowmeters under different working conditions.}, } @article {pmid37231052, year = {2023}, author = {Li, S and Mao, L and Alizadeh, A and Zhang, X and Mousavi, SV}, title = {The application of non-uniform magnetic field for thermal enhancement of the nanofluid flow inside the U-turn pipe at solar collectors.}, journal = {Scientific reports}, volume = {13}, number = {1}, pages = {8471}, pmid = {37231052}, issn = {2045-2322}, abstract = {The improvement of heat transfer inside the solar heat exchangers is important for the development of solar energy in an urban area. In this study, the usage of a non-uniform magnetic field on the thermal efficiency of the nanofluid (Fe3O4) streaming inside the U-turn pipe of solar heat exchangers is examined. Computational fluid dynamic is applied to visualize the nanofluid flow inside the solar heat exchanger. The role of magnetic intensity and Reynolds number on thermal efficiency are fully investigated. The effect of single and triple sources of the magnetic field is also studied in our research. Obtained results indicate that the usage of the magnetic field results in the production of vortex in the base fluid and heat transfer improves inside the domain. Our finding indicates that the usage of the magnetic field with Mn = 25 K would improve the average heat transfer by about 21% along the U-turn pipe of solar heat exchangers.}, } @article {pmid37230014, year = {2023}, author = {Yeom, J and Park, J and Park, JY}, title = {Fluid dynamic simulation for cellular damage due to lymphatic flow within the anatomical arrangement of the outer hair cells in the cochlea.}, journal = {Computers in biology and medicine}, volume = {161}, number = {}, pages = {106986}, doi = {10.1016/j.compbiomed.2023.106986}, pmid = {37230014}, issn = {1879-0534}, mesh = {Humans ; *Hair Cells, Auditory, Outer/physiology ; *Hydrodynamics ; Cochlea/physiology ; Hair Cells, Auditory, Inner/physiology ; }, abstract = {Damage to the sensory hair cells in the cochlea is a major cause of hearing loss since human sensory hair cells do not regenerate naturally after damage. As these sensory hair cells are exposed to a vibrating lymphatic environment, they may be affected by physical flow. It is known that the outer hair cells (OHCs) are physically more damaged by sound than the inner hair cells (IHCs). In this study, the lymphatic flow is compared using computational fluid dynamics (CFD) based on the arrangement of the OHCs, and the effects of such flow on the OHCs is analyzed. In addition, flow visualization is used to validate the Stokes flow. The Stokes flow behavior is attributed to the low Reynolds number, and the same behavior is observed even when the flow direction is reversed. When the distance between the rows of the OHCs is large, each row is independent, but when this distance is short, the flow change in each row influences the other rows. The stimulation caused by flow changes on the OHCs is confirmed through surface pressure and shear stress. The OHCs located at the base with a short distance between the rows receive excess hydrodynamic stimulation, and the tip of the V-shaped pattern receives an excess mechanical force. This study attempts to understand the contributions of lymphatic flow to OHC damage by quantitatively suggesting stimulation of the OHCs and is expected to contribute to the development of OHC regeneration technologies in the future.}, } @article {pmid37220708, year = {2023}, author = {Tisdell, CC}, title = {Improved perturbation solution for two-dimensional viscous flow between expanding or contracting permeable walls.}, journal = {Journal of biomechanics}, volume = {155}, number = {}, pages = {111642}, doi = {10.1016/j.jbiomech.2023.111642}, pmid = {37220708}, issn = {1873-2380}, mesh = {Viscosity ; *Physical Examination ; }, abstract = {Despite the continuing interest in the transport of biological fluid within contracting or expanding vessels, our knowledge is yet to be fully developed, even in the two-dimensional case. For example, explicit solutions and close approximations to these models remain unknown, and the physical problem has been restricted to the "slow" expansion or contraction of the walls. Thus, the purpose of this short communication is to partially address such challenges and gaps by generating explicit solutions and improving approximations to the flow problem without the "slowness" restriction being imposed. We show that when the Reynolds number is zero (i.e., the inviscid case), the corresponding homogeneous differential equation under consideration may be completely solved. We then illustrate how this exact solution may be leveraged to form more precise approximations to the flow via perturbation techniques when the Reynolds number is small. Our perturbation approach is only in one parameter (the Reynolds number) instead of the usual two parameters (the Reynolds number and wall dilation rate), and thus we make no restriction regarding the "slowness" of wall expansion or contraction for our general perturbation scheme. Our act of "shining new light through old windows" improves and extends the results of Majdalani, Zhou and Dawson and, moreover, our method has significant potential to be applied by researchers to form more precise one-parameter perturbation approximations to flow problems in contrast to the limitations of the traditional two-parameter perturbation approaches that have dominated the literature.}, } @article {pmid37215871, year = {2023}, author = {Zhao, L and Wang, Y and Qi, Z}, title = {Investigation of periodic characteristics of perturbed flow over a slender body.}, journal = {Heliyon}, volume = {9}, number = {5}, pages = {e16194}, pmid = {37215871}, issn = {2405-8440}, abstract = {The asymmetric flow over a slender body was particularly sensitive to the nose at a high angle of attack (AoA). Two patterns of separation occurred on the noses of the pointed-nosed slender body and blunt-nosed slender body as open- and close-type separation, respectively. The effects of the bluntness were investigated at high AoA (α = 50°) to clarify the evolution of the separated pattern from open-to close-type separation by the nose and by the periodic characteristics of perturbed flow. Wind tunnel experimental tests were conducted to investigate the periodic characteristics of asymmetric flow at a Reynolds number ReD = 1.54 × 10[5], based on incoming free-stream velocity (U∞) and the diameter (D) of the model. A particle was attached to the tip of the nose to induce the perturbed flow and attain a definite and predictable asymmetric flow in experimental tests. The pressure scanning and surface oil-flow visualization techniques were used to capture the pressure distributions and flow separations. The major findings were that axial flow increases with the increase of bluntness, resulting in open-type separation turning into close-type separation, and the perturbation moved from downstream to upstream of starting points of the separation line. The critical bluntness of separation pattern switching from open-type to close-type located between 1.5 and 3. Thus, the management of perturbation on asymmetric flow pattern switched from directly participating in separation to influencing separation through micro-flow. Therefore, the locations of perturbation and starting points of the separation line were closely related to asymmetric flow management by perturbation, then affecting the periodic characteristics of perturbed flow.}, } @article {pmid37198775, year = {2023}, author = {Yoo, H and Wissocq, G and Jacob, J and Favier, J and Sagaut, P}, title = {Compressible lattice Boltzmann method with rotating overset grids.}, journal = {Physical review. E}, volume = {107}, number = {4-2}, pages = {045306}, doi = {10.1103/PhysRevE.107.045306}, pmid = {37198775}, issn = {2470-0053}, abstract = {The numerical instability of the lattice Boltzmann method (LBM) at high Mach or high Reynolds number flow is well identified, and it remains a major barrier to its application in more complex configurations such as moving geometries. This work combines the compressible lattice Boltzmann model with rotating overset grids (the so-called Chimera method, sliding mesh, or moving reference frame) for high Mach flows. This paper proposes to use the compressible hybrid recursive regularized collision model with fictitious forces (or inertial forces) in a noninertial rotating reference frame. Also, polynomial interpolations are investigated, which allow fixed inertial and rotating noninertial grids to communicate with each other. We suggest a way to effectively couple the LBM with the MUSCL-Hancock scheme in the rotating grid, which is needed to account for thermal effect of compressible flow. As a result, this approach is demonstrated to have an extended Mach stability limit for the rotating grid. It also demonstrates that this complex LBM scheme can maintain the second-order accuracy of the classic LBM by appropriately using numerical methods like polynomial interpolations and the MUSCL-Hancock scheme. Furthermore, the method shows a very good agreement on aerodynamic coefficients compared to experiments and the conventional finite-volume scheme. This work presents a thorough academic validation and error analysis of the LBM for simulating moving geometries in high Mach compressible flows.}, } @article {pmid37190405, year = {2023}, author = {Niven, RK}, title = {Dimensionless Groups by Entropic Similarity: I - Diffusion, Chemical Reaction and Dispersion Processes.}, journal = {Entropy (Basel, Switzerland)}, volume = {25}, number = {4}, pages = {}, pmid = {37190405}, issn = {1099-4300}, abstract = {Since the time of Buckingham in 1914, dimensional analysis and similarity arguments based on dimensionless groups have served as powerful tools for the analysis of systems in all branches of science and engineering. Dimensionless groups are generally classified into those arising from geometric similarity, based on ratios of length scales; kinematic similarity, based on ratios of velocities or accelerations; and dynamic similarity, based on ratios of forces. We propose an additional category of dimensionless groups based on entropic similarity, defined by ratios of (i) entropy production terms; (ii) entropy flow rates or fluxes; or (iii) information flow rates or fluxes. Since all processes involving work against friction, dissipation, diffusion, dispersion, mixing, separation, chemical reaction, gain of information or other irreversible changes are driven by (or must overcome) the second law of thermodynamics, it is appropriate to analyze them directly in terms of competing entropy-producing and transporting phenomena and the dominant entropic regime, rather than indirectly in terms of forces. In this study, entropic groups are derived for a wide variety of diffusion, chemical reaction and dispersion processes relevant to fluid mechanics, chemical engineering and environmental engineering. It is shown that many dimensionless groups traditionally derived by kinematic or dynamic similarity (including the Reynolds number) can also be recovered by entropic similarity-with a different entropic interpretation-while many new dimensionless groups can also be identified. The analyses significantly expand the scope of dimensional analysis and similarity arguments for the resolution of new and existing problems in science and engineering.}, } @article {pmid37186956, year = {2023}, author = {Guo, Q and Zhang, J and Li, D and Yu, H}, title = {Effect of Wettability on the Collision Behavior of Acoustically Excited Droplets.}, journal = {Langmuir : the ACS journal of surfaces and colloids}, volume = {39}, number = {21}, pages = {7408-7417}, doi = {10.1021/acs.langmuir.3c00571}, pmid = {37186956}, issn = {1520-5827}, abstract = {Acoustic droplet ejection (ADE) is a noncontact technique for micro-liquid handling (usually nanoliters or picoliters) that is not restricted by nozzles and enables high-throughput liquid dispensing without sacrificing precision. It is widely regarded as the most advanced solution for liquid handling in large-scale drug screening. Stable coalescence of the acoustically excited droplets on the target substrate is a fundamental requirement during the application of the ADE system. However, it is challenging to investigate the collision behavior of nanoliter droplets flying upward during the ADE. In particular, the dependence of the droplet's collision behavior on substrate wettability and droplet velocity has yet to be thoroughly analyzed. In this paper, the kinetic processes of binary droplet collisions were investigated experimentally for different wettability substrate surfaces. Four states occur as the droplet collision velocity increases: coalescence after minor deformation, complete rebound, coalescence during rebound, and direct coalescence. For the hydrophilic substrate, there are wider ranges of Weber number (We) and Reynolds number (Re) in the complete rebound state. And with the decrease of the substrate wettability, the critical Weber and Reynolds numbers for the coalescence during rebound and the direct coalescence decrease. It is further revealed that the hydrophilic substrate is susceptible to droplet rebound because the sessile droplet has a larger radius of curvature and the viscous energy dissipation is greater. Besides, the prediction model of the maximum spreading diameter was established by modifying the droplet morphology in the complete rebound state. It is found that, under the same Weber and Reynolds numbers, droplet collisions on the hydrophilic substrate achieve a smaller maximum spreading coefficient and greater viscous energy dissipation, so the hydrophilic substrate is prone to droplet bounce.}, } @article {pmid37123410, year = {2023}, author = {Ishimoto, K and Gaffney, EA and Smith, DJ}, title = {Squirmer hydrodynamics near a periodic surface topography.}, journal = {Frontiers in cell and developmental biology}, volume = {11}, number = {}, pages = {1123446}, pmid = {37123410}, issn = {2296-634X}, abstract = {The behaviour of microscopic swimmers has previously been explored near large-scale confining geometries and in the presence of very small-scale surface roughness. Here, we consider an intermediate case of how a simple microswimmer, the tangential spherical squirmer, behaves adjacent to singly and doubly periodic sinusoidal surface topographies that spatially oscillate with an amplitude that is an order of magnitude less than the swimmer size and wavelengths that are also within an order of magnitude of this scale. The nearest neighbour regularised Stokeslet method is used for numerical explorations after validating its accuracy for a spherical tangential squirmer that swims stably near a flat surface. The same squirmer is then introduced to different surface topographies. The key governing factor in the resulting swimming behaviour is the size of the squirmer relative to the surface topography wavelength. For instance, directional guidance is not observed when the squirmer is much larger, or much smaller, than the surface topography wavelength. In contrast, once the squirmer size is on the scale of the topography wavelength, limited guidance is possible, often with local capture in the topography troughs. However, complex dynamics can also emerge, especially when the initial configuration is not close to alignment along topography troughs or above topography crests. In contrast to sensitivity in alignment and topography wavelength, reductions in the amplitude of the surface topography or variations in the shape of the periodic surface topography do not have extensive impacts on the squirmer behaviour. Our findings more generally highlight that the numerical framework provides an essential basis to elucidate how swimmers may be guided by surface topography.}, } @article {pmid37115869, year = {2023}, author = {Ambruş, VE and Schlichting, S and Werthmann, C}, title = {Establishing the Range of Applicability of Hydrodynamics in High-Energy Collisions.}, journal = {Physical review letters}, volume = {130}, number = {15}, pages = {152301}, doi = {10.1103/PhysRevLett.130.152301}, pmid = {37115869}, issn = {1079-7114}, abstract = {We simulate the space-time dynamics of high-energy collisions based on a microscopic kinetic description in the conformal relaxation time approximation, in order to determine the range of applicability of an effective description in relativistic viscous hydrodynamics. We find that hydrodynamics provides a quantitatively accurate description of collective flow when the average inverse Reynolds number Re^{-1} is sufficiently small and the early preequilibrium stage is properly accounted for. We further discuss the implications of our findings for the (in)applicability of hydrodynamics in proton-proton, proton-nucleus, and light nucleus collisions.}, } @article {pmid37112102, year = {2023}, author = {Lin, W and Li, Z and Zhang, S and Lin, J}, title = {Numerical Study on the Distribution of Rodlike Particles in Laminar Flows of Power Law Fluids Past a Cylinder.}, journal = {Polymers}, volume = {15}, number = {8}, pages = {}, pmid = {37112102}, issn = {2073-4360}, support = {12132015//National Natural Science Foundation of China/ ; }, abstract = {The contraction/expansion laminar flow containing rodlike particles in power-law fluid is studied numerically when the particles are in a dilute phase. The fluid velocity vector and streamline of flow are given at the finite Reynolds number (Re) region. The effects of Re, power index n and particle aspect ratio β on the spatial and orientation distributions of particles are analyzed. The results showed that for the shear-thickening fluid, particles are dispersed in the whole area in the contraction flow, while more particles are gathered near the two walls in the expansion flow. The spatial distribution of particles with small β is more regular. Β has a significant, n has a moderate, but Re has a small impact on the spatial distribution of particles in the contraction and expansion flow. In the case of large Re, most particles are oriented in the flow direction. The particles near the wall show obvious orientation along the flow direction. In shear-thickening fluid, when the flow changes from contraction to expansion, the orientation distribution of particles becomes more dispersed; while in shear-thinning fluid, the opposite is true. More particles orient to the flow direction in expansion flow than that in contraction flow. The particles with a large β tend to align with the flow direction more obviously. Re, n and β have great influence on the orientation distribution of particles in the contraction and expansion flow. Whether the particles initially located at the inlet can bypass the cylinder depends on the transverse position and initial orientation of the particles at the inlet. The number of particles with θ0 = 90° bypassing the cylinder is the largest, followed by θ0 = 45° and θ0 = 0°. The conclusions obtained in this paper have reference value for practical engineering applications.}, } @article {pmid37100809, year = {2023}, author = {Pilloton, C and Lugni, C and Graziani, G and Fedele, F}, title = {Wave dispersion in moderate channel turbulence.}, journal = {Scientific reports}, volume = {13}, number = {1}, pages = {6801}, pmid = {37100809}, issn = {2045-2322}, abstract = {We study channel turbulence by interpreting its vorticity as a random sea of ocean wave packet analogues. In particular, we investigate the ocean-like properties of vortical packets applying stochastic methods developed for oceanic fields. Taylor's hypothesis of frozen eddies does not hold when turbulence is not weak, and vortical packets change shape as they are advected by the mean flow, altering their own speed. This is the physical manifestation of a hidden wave dispersion of turbulence. Our analysis at the bulk Reynolds number Reb = 5600 suggests that turbulent fluctuations behave dispersively as gravity-capillary waves, with capillarity being dominant near the wall region.}, } @article {pmid37097943, year = {2023}, author = {Prasad, V and Sharma, A and Kulkarni, SS}, title = {Chaotic advection in a recirculating flow: Effect of a fluid multiple-flexible-solid interaction.}, journal = {Chaos (Woodbury, N.Y.)}, volume = {33}, number = {4}, pages = {}, doi = {10.1063/5.0132986}, pmid = {37097943}, issn = {1089-7682}, abstract = {This paper deals with chaotic advection due to a two-way interaction between flexible elliptical-solids and a laminar lid-driven cavity flow in two dimensions. The present Fluid multiple-flexible-Solid Interaction study involves various number N(= 1-120) of equal-sized neutrally buoyant elliptical-solids (aspect ratio β = 0.5) such that they result in the total volume fraction Φ = 10 % as in our recent study on single solid, done for non-dimensional shear modulus G ∗ = 0.2 and Reynolds number R e = 100. Results are presented first for flow-induced motion and deformation of the solids and later for chaotic advection of the fluid. After the initial transients, the fluid as well as solid motion (and deformation) attain periodicity for smaller N ≤ 10 while they attain aperiodic states for larger N > 10. Adaptive material tracking (AMT) and Finite-Time Lyapunov Exponent (FTLE)-based Lagrangian dynamical analysis revealed that the chaotic advection increases up to N = 6 and decreases at larger N(= 6-10) for the periodic state. Similar analysis for the transient state revealed an asymptotic increase in the chaotic advection with increasing N ≤ 120. These findings are demonstrated with the help of two types of chaos signatures: exponential growth of material blob's interface and Lagrangian coherent structures, revealed by the AMT and FTLE, respectively. Our work, which is relevant to several applications, presents a novel technique based on the motion of multiple deformable-solids for enhancement of chaotic advection.}, } @article {pmid37092929, year = {2023}, author = {Yang, C and Arcondoulis, EJG and Yang, Y and Guo, J and Maryami, R and Bi, C and Liu, Y}, title = {Active control of airfoil turbulent boundary layer noise with trailing-edge blowing.}, journal = {The Journal of the Acoustical Society of America}, volume = {153}, number = {4}, pages = {2115}, doi = {10.1121/10.0017787}, pmid = {37092929}, issn = {1520-8524}, abstract = {Large Eddy Simulation (LES) and Ffowcs Williams-Hawkings acoustic analogy are performed to study the effect of trailing-edge blowing on airfoil self-noise. Simulations were conducted using a National Advisory Committee for Aeronautics 0012 airfoil at zero angle of attack and a chord-based Reynolds number of 4 × 10 5. The aerodynamic and aeroacoustic characteristics of the baseline airfoil were thoroughly verified by comparison with previous numerical and experimental data. The noise reduction effects of continuous and local blowing with different blowing ratios and blowing momentum coefficients were compared. A maximum noise reduction of 20 dB was achieved via trailing-edge blowing and the noise reduction mechanisms of the two blowing methods were discussed. The LES results show a pair of recirculation bubbles in the airfoil wake which are suppressed by trailing-edge blowing. As the blowing vortices convect into the wake, they stretch and stabilize the shear flows from airfoil surfaces. Instantaneous vorticity and root mean square velocity fluctuations are also weakened. There is a decrease in the spanwise coherence and an increase in the phase difference, which contribute to noise reduction. It is concluded that the suppression of turbulence fluctuations in the near wake is the main mechanism of noise reduction for airfoil trailing-edge blowing.}, } @article {pmid37073470, year = {2023}, author = {Roggeveen, JV and Stone, HA and Kurzthaler, C}, title = {Transport of a passive scalar in wide channels with surface topography: An asymptotic theory.}, journal = {Journal of physics. Condensed matter : an Institute of Physics journal}, volume = {35}, number = {27}, pages = {}, doi = {10.1088/1361-648X/acc8ad}, pmid = {37073470}, issn = {1361-648X}, abstract = {We generalize classical dispersion theory for a passive scalar to derive an asymptotic long-time convection-diffusion equation for a solute suspended in a wide, structured channel and subject to a steady low-Reynolds-number shear flow. Our asymptotic theory relies on a domain perturbation approach for small roughness amplitudes of the channel and holds for general surface shapes expandable as a Fourier series. We determine an anisotropic dispersion tensor, which depends on the characteristic wavelengths and amplitude of the surface structure. For surfaces whose corrugations are tilted with respect to the applied flow direction, we find that dispersion along the principal direction (i.e. the principal eigenvector of the dispersion tensor) is at an angle to the main flow direction and becomes enhanced relative to classical Taylor dispersion. In contrast, dispersion perpendicular to it can decrease compared to the short-time diffusivity of the particles. Furthermore, for an arbitrary surface shape represented in terms of a Fourier decomposition, we find that each Fourier mode contributes at leading order a linearly-independent correction to the classical Taylor dispersion diffusion tensor.}, } @article {pmid37069324, year = {2023}, author = {Nyatchouba Nsangue, BT and Tang, H and Liu, W and Xu, L and Hu, F}, title = {Turbulent flow interacting with flexible trawl net structure including simulation catch in flume tank.}, journal = {Scientific reports}, volume = {13}, number = {1}, pages = {6249}, pmid = {37069324}, issn = {2045-2322}, support = {Grant No. 31902426//National Natural Science Foundation of China/ ; 19YF1419800//Shanghai Sailing Program/ ; D-8002-18-0097//Special Project for the Exploitation and Utilization of Antarctic Biological Resources of the Ministry of Agriculture and Rural Affairs/ ; }, abstract = {The interaction between fluid and the midwater trawl with stocked catches is extremely complex, but essential to improve the understanding of the drag force acting on the trawl, the behavior of the fishing structure during a trawling process, and to predict its selectivity process. The present study assesses the turbulent characteristics inside and around the midwater trawls with catch and without catch linked to its fluttering motion. The analysis is based on three-dimensional electromagnetic current velocity meter measurements performed in the multiple points inside and outside different parts of a 1/35 scaled midwater trawl model with the aim of access the main turbulent flow structure inside and around the gear. Time-averaged normalized flow velocity fields and turbulent flow parameters were analyzed from the measured flow data. Furthermore, Fourier analysis was conducted by watching the time-frequency Power spectrum content of instantaneous flow velocities fields, the fluttering trawl motions, turbulent kinetic energy, and momentum flux. Based on successive analyzes of mean flow characteristics and turbulent flow parameters, it has been demonstrated that the presence of catch inside the trawl net impacts the evolution of unsteady turbulent flow by creating large trawl fluttering motions that strongly affect the flow passage. The results showed that the time-averaged normalized streamwise and transverse flow velocities inside and around the trawl net with catch were 12.41% lower compared with that obtained inside and around the trawl without catch. The turbulent length scale and turbulent Reynolds number obtained in the different part of the trawl net with catch were about 33.05% greater than those obtained on the trawl net without catch, confirming that the unsteady turbulent flow developing inside and around the midwater trawl is influence by the catch and liner. It is observed that the motions of both the trawl without catch and the trawl with catch are mainly of a low-frequency activity and another component related to unsteady turbulent flow street. A complex fluid-structure interaction is then demonstrated where the fluttering motions of the trawl net affect the fluid flow inside and around trawl net, the fluid force, turbulent pattern, and simultaneously, the periodic unsteady turbulent flow influence the trawl motions.}, } @article {pmid37064396, year = {2023}, author = {Ding, Y and Liu, Z and Wang, X and Xin, R and Shan, D and He, B and Jing, J and Gao, Q and Yang, J and Chen, Y}, title = {Validation of hemodynamic stress calculation in coronary computed tomography angiography versus intravascular ultrasound.}, journal = {Quantitative imaging in medicine and surgery}, volume = {13}, number = {4}, pages = {2339-2351}, pmid = {37064396}, issn = {2223-4292}, abstract = {BACKGROUND: Development in computational fluid dynamics and 3D construction could facilitate the calculation of hemodynamic stresses in coronary computed tomography angiography (CCTA). However, the agreement between CCTA derived stresses and intravascular ultrasound/intravascular coronary angiography (IVUS/ICA)-derived stresses remains undetermined. Thus, the purpose of this study is to investigate if CCTA can serve as alternative to IVUS/ICA for hemodynamic evaluation.

METHODS: In this retrospective study, 13 patients (14 arteries) with unstable angina who underwent both CCTA and IVUS/ICA at an interval of less than 7 days were consecutively included at the Chinese PLA General Hospital within the year of 2021. Slice-level minimal lumen area (MLA), percent area stenosis, velocity, pressure, Reynolds number, wall shear stress (WSS) and axial plaque stress (APS) were determined by both modalities. The agreement between CCTA and IVUS/ICA was assessed using the intraclass correlation coefficient (ICC), Pearson's correlation coefficient and Bland-Altman analysis.

RESULTS: CCTA overestimated the degree of area stenosis (50.22%±16.15% vs. 36.41%±19.37%, P=0.004) with the MLA showing no significant difference (5.81±2.24 vs. 6.72±2.04 mm[2], P=0.126). No statistical difference was observed in WSS (6.57±6.26 vs. 5.98±5.55 Pa, P=0.420) and APS (16.03±1,159.45 vs. -1.27±890.39 Pa, P=0.691) between CCTA and IVUS. Good correlation was found in velocity (ICC: 0.796, 95% CI: 0.752-0.833), Reynolds number (ICC: 0.810, 95% CI: 0.768-0.844) and WSS (ICC: 0.769, 95% CI: 0.718-0.810), while the ICC of APS was (ICC: 0.341, 95% CI: 0.197-0.458), indicating a relatively poor correlation.

CONCLUSIONS: CCTA can serve as a satisfactory alternative to the reference standard, IVUS/ICA in morphology simulation and hemodynamic stress calculation, especially in the calculation of WSS.}, } @article {pmid37039923, year = {2023}, author = {Guastoni, L and Rabault, J and Schlatter, P and Azizpour, H and Vinuesa, R}, title = {Deep reinforcement learning for turbulent drag reduction in channel flows.}, journal = {The European physical journal. E, Soft matter}, volume = {46}, number = {4}, pages = {27}, pmid = {37039923}, issn = {1292-895X}, support = {2021-CoG-101043998/ERC_/European Research Council/International ; }, abstract = {We introduce a reinforcement learning (RL) environment to design and benchmark control strategies aimed at reducing drag in turbulent fluid flows enclosed in a channel. The environment provides a framework for computationally efficient, parallelized, high-fidelity fluid simulations, ready to interface with established RL agent programming interfaces. This allows for both testing existing deep reinforcement learning (DRL) algorithms against a challenging task, and advancing our knowledge of a complex, turbulent physical system that has been a major topic of research for over two centuries, and remains, even today, the subject of many unanswered questions. The control is applied in the form of blowing and suction at the wall, while the observable state is configurable, allowing to choose different variables such as velocity and pressure, in different locations of the domain. Given the complex nonlinear nature of turbulent flows, the control strategies proposed so far in the literature are physically grounded, but too simple. DRL, by contrast, enables leveraging the high-dimensional data that can be sampled from flow simulations to design advanced control strategies. In an effort to establish a benchmark for testing data-driven control strategies, we compare opposition control, a state-of-the-art turbulence-control strategy from the literature, and a commonly used DRL algorithm, deep deterministic policy gradient. Our results show that DRL leads to 43% and 30% drag reduction in a minimal and a larger channel (at a friction Reynolds number of 180), respectively, outperforming the classical opposition control by around 20 and 10 percentage points, respectively.}, } @article {pmid37037634, year = {2023}, author = {Wang, YH and Lin, XY and Cheng, Y and Wang, H and Liu, W and Zhuge, XK and Huo, XL and Bao, N}, title = {Vibration for enhancement of electrochemical analysis of biomolecules in a droplet on the rough surface of a disposable working electrode.}, journal = {Analytica chimica acta}, volume = {1256}, number = {}, pages = {341158}, doi = {10.1016/j.aca.2023.341158}, pmid = {37037634}, issn = {1873-4324}, mesh = {*Vibration ; *Electrochemical Techniques/methods ; Electrodes ; }, abstract = {Although electrochemical detection of microliters-level solutions is attractive for analysis of low-amount biological samples, its performance could be weakened by limited mass transfer due to low Reynolds number and laminar flow. Herein we designed a 3D-printed electroanalytical device to apply vibration for improvement of mass transfer during electrochemical detection. In our approach, the droplet-size sample solution containing Indole-3-acetic acid (IAA, as a model) was directly applied on the effective surface of a disposable working electrode. We demonstrated that vibration could enhance electrochemical responses of IAA more on the rough surface than on the smooth surface of the working electrodes. After optimization, the sensitivity for electrochemical detection of a 20-μL droplet under vibration with the voltage of 7 V increased more than 100% compared with the static condition. The enhanced electrochemical responses brought by vibration could be achieved reproducibly, which could be ascribed to improved mass transfer. Our strategy could be practically applied for differentiation of IAA in different tissues of Marchantia polymorpha with enhanced responses. This study suggested that vibration might become a simple and effective method to improve mass transfer in analysis of microliter-volume solutions, which might be extended for more biochemical assays.}, } @article {pmid37034318, year = {2023}, author = {Dyverfeldt, P and Trenti, C and Ziegler, M and Bjarnegård, N and Lindenberger, M}, title = {Helical flow in tortuous aortas and its relationship to turbulence: A whole-aorta 4D flow MRI study.}, journal = {Frontiers in cardiovascular medicine}, volume = {10}, number = {}, pages = {1124604}, pmid = {37034318}, issn = {2297-055X}, abstract = {BACKGROUND: Increased vascular tortuosity is a hallmark of ageing of the vascular system, including the aorta. However, the impact of tortuosity on aortic blood flow is unknown. We hypothesized that increased tortuosity would be associated with increased blood flow helicity and with decreased degree of blood flow turbulence as measured by the turbulent kinetic energy (TKE).

METHODS: 4D Flow MR images covering the entire aorta from the aortic valve to the iliac bifurcation were acquired in 23 normal volunteers aged 18-30 years ("Young") and 23 normal volunteers aged 66-76 years ("Old") without aortic disease. The aorta was segmented and divided into four regions: the ascending, descending, suprarenal abdominal and infrarenal abdominal aorta. Tortuosity, helicity, TKE, flow velocity, and Reynolds number were computed for the whole aorta and for each section.

RESULTS: Tortuosity and helicity were higher whereas TKE, velocity, and Reynolds number were lower in Old than in Young, for all aortic regions (p < 0.05) except for helicity in the descending aorta. Tortuosity correlated positively with helicity and negatively with TKE for all aortic regions (Spearman rho=±0.45-±0.72, p < =0.002) except for TKE in the ascending aorta. Further, helicity correlated with TKE in the descending, suprarenal abdominal and infrarenal abdominal aorta (Spearman rho=-0.56--0.77).

CONCLUSION: Tortuosity increases with age and blood flow in tortuous aortas is more helical. Increasing helicity, in turn, is associated with decreasing TKE.}, } @article {pmid37033871, year = {2023}, author = {Meng, M and Yang, Q}, title = {Investigation of the Microscopic Process of the Media Coalescence Treatment of Water-in-Oil Emulsion.}, journal = {ACS omega}, volume = {8}, number = {13}, pages = {11908-11915}, pmid = {37033871}, issn = {2470-1343}, abstract = {Medium coalescence technology is a research hotspot for the separation of oil-in-water emulsions. However, the coalescence mechanism is still unclear, making it challenging to effectively improve the separation performance. Herein, the microscopic mechanism of medium coalescence was revealed. We found that the effective collision positions under the action of the flow field include the exposed granule surface, adherent droplet surface, and three-phase contact line. Furthermore, a numerical model of the microscopic process of water-in-oil emulsion permeation through a granular bed was established. The effects of different parameters (including the number of medium layers, Reynolds number, and inlet concentration) on the microscopic process of capturing dispersed-phase droplets in the bed and the pressure drop in the coalescence area were studied. The numerical results show that the droplets form the bridging structure between the granules. On the one hand, the bridging structure promotes the capture of the droplets by the bed; on the other hand, it causes pressure-drop fluctuations in the coalescence area and asymmetric distribution of the velocity field.}, } @article {pmid37029144, year = {2023}, author = {Abdelhafez, MA and Abd-Alla, AM and Abo-Dahab, SM and Elmhedy, Y}, title = {Influence of an inclined magnetic field and heat and mass transfer on the peristaltic flow of blood in an asymmetric channel.}, journal = {Scientific reports}, volume = {13}, number = {1}, pages = {5749}, pmid = {37029144}, issn = {2045-2322}, mesh = {*Hot Temperature ; Rheology/methods ; *Models, Theoretical ; Temperature ; Peristalsis ; }, abstract = {This article presents a theoretical study on heat and mass transfer analysis of the peristaltic flow of blood conveying through an asymmetric channel in the presence of inclined to the magnetic field. The effects of ratio of relaxation to retardation times, non-uniform parameter, the non-dimensional amplitude, Hartman number and phase difference have been taken into account. The governing coupled non-linear partial differential equations representing the flow model are transmuted into linear ones by assuming that the wave is very long with a small Reynolds number. The converted mathematical formulations are solved analytically via the Mathematica software. Analytical expressions for the dimensionless velocity profiles of fluid, temperature, concentration, pressure gradient, increase in pressure, heat transfer coefficient and shear stress of the blood are derived. The velocity, temperature, concentration, pressure gradient, increase in pressure, heat transfer coefficient and shear stress were calculated numerically for different values of the parameters, which were represented graphically and find their physical meaning.}, } @article {pmid37025873, year = {2023}, author = {Nishu, IZ and Samad, MF}, title = {Modeling and simulation of a split and recombination-based passive micromixer with vortex-generating mixing units.}, journal = {Heliyon}, volume = {9}, number = {4}, pages = {e14745}, pmid = {37025873}, issn = {2405-8440}, abstract = {As a state-of-the-art technology, micromixers are being used in various chemical and biological processes, including polymerization, extraction, crystallization, organic synthesis, biological screening, drug development, drug delivery, etc. The ability of a micromixer to perform efficient mixing while consuming little power is one of its basic needs. In this paper, a passive micromixer having vortex-generating mixing units is proposed which shows effective mixing with a small pressure drop. The micromixer works on the split and recombination (SAR) flow principle. In this study, four micromixers are designed with different arrangements of mixing units, and the effect of the placement of connecting channels is evaluated in terms of mixing index, pressure drop, and mixing performance. The channel width of 200 μm, height of 300 μm, and size of mixing units are maintained constant for all the micromixers throughout the evaluation process. The numerical simulation is performed for the Reynolds number (Re) range of 0.1-100 using Comsol Multiphysics software. By categorizing the flow patterns into three regimes based on the range of Re, the fluid flow throughout the length of the micromixer is visualized. The micromixer with dislocated connecting channels provides a satisfactory result with the mixing index of 0.96 and 0.94, and the pressure drop of 2.5 Pa and 7.8 kPa at Re = 0.1 and Re = 100 respectively. It also outperformed the other models in terms of the mixing performance. The proposed micromixer might very well be used in microfluidic devices for a variety of analytical procedures due to its straightforward construction and outstanding performance.}, } @article {pmid37018723, year = {2023}, author = {Van Impe, M and Caboor, L and Deleeuw, V and Olbinado, M and De Backer, J and Sips, P and Segers, P}, title = {Fluid-Structure Interaction Modeling of the Aortic Hemodynamics in Adult Zebrafish: A Pilot Study Based on Synchrotron X-Ray Tomography.}, journal = {IEEE transactions on bio-medical engineering}, volume = {70}, number = {7}, pages = {2101-2110}, doi = {10.1109/TBME.2023.3236488}, pmid = {37018723}, issn = {1558-2531}, mesh = {Adult ; Humans ; Animals ; Mice ; *Zebrafish ; Pilot Projects ; *Cardiovascular Diseases ; Synchrotrons ; Aorta/diagnostic imaging ; Hemodynamics ; Tomography, X-Ray Computed ; Models, Cardiovascular ; Stress, Mechanical ; }, abstract = {OBJECTIVE: The zebrafish is increasingly used as a small animal model for cardiovascular disease, including vascular disorders. Nevertheless, a comprehensive biomechanical understanding of the zebrafish cardiovascular circulation is still lacking and possibilities for phenotyping the zebrafish heart and vasculature at adult - no longer optically transparent - stages are limited. To improve these aspects, we developed imaging-based 3D models of the cardiovascular system of wild-type adult zebrafish.

METHODS: In vivo high-frequency echocardiography and ex vivo synchrotron X-ray tomography were combined to build fluid-structure interaction finite element models of the fluid dynamics and biomechanics inside the ventral aorta.

RESULTS: We successfully generated a reference model of the circulation in adult zebrafish. The dorsal side of the most proximal branching region was found as the location of highest first principal wall stress and was also a location of low wall shear stress. Reynolds number and oscillatory shear were very low compared to mice and humans.

SIGNIFICANCE: The presented wild-type results provide a first extensive biomechanical reference for adult zebrafish. This framework can be used for advanced cardiovascular phenotyping of adult genetically engineered zebrafish models of cardiovascular disease, showing disruptions of the normal mechano-biology and homeostasis. By providing reference values for key biomechanical stimuli (including wall shear stress and first principal stress) in wild-type animals, and a pipeline for image-based animal-specific computational biomechanical models, this study contributes to a more comprehensive understanding of the role of altered biomechanics and hemodynamics in heritable cardiovascular pathologies.}, } @article {pmid37012373, year = {2023}, author = {Lee, S and Bui-Vinh, D and Baek, M and Kwak, DB and Lee, H}, title = {Modeling pressure drop values across ultra-thin nanofiber filters with various ranges of filtration parameters under an aerodynamic slip effect.}, journal = {Scientific reports}, volume = {13}, number = {1}, pages = {5449}, pmid = {37012373}, issn = {2045-2322}, abstract = {Computational fluid dynamics simulations of fibrous filters with 56 combinations of different fiber sizes, packing densities, face velocities, and thicknesses were conducted for developing models that predict pressure drops across nanofiber filters. The accuracy of the simulation method was confirmed by comparing the numerical pressure drops to the experimental data obtained for polyacrylonitrile electrospun nanofiber filters. In the simulations, an aerodynamic slip effect around the surface of the small nanofibers was considered. The results showed that, unlike in the case of conventional filtration theory, pressure drops across the thin layers of electrospun nanofiber filters are not proportional to the thickness. This might be a critical factor for obtaining precise pressure drops across the electrospun nanofiber filters with extremely thin layers. Finally, we derived the product of drag coefficient and Reynolds number as a function of packing density, Knudsen number, and ratio of thickness to fiber diameter to get the correlation equation for pressure drop prediction. The obtained equation predicted the pressure drops across the nanofiber filters with the maximum relative difference of less than 15%.}, } @article {pmid37009788, year = {2023}, author = {Connor, AA and Webster, DR}, title = {Hydrodynamics of the fast-start caridoid escape response in Antarctic krill, Euphausia superba.}, journal = {Scientific reports}, volume = {13}, number = {1}, pages = {5376}, pmid = {37009788}, issn = {2045-2322}, mesh = {Animals ; *Euphausiacea/physiology ; Hydrodynamics ; Swimming/physiology ; Biomechanical Phenomena ; Antarctic Regions ; }, abstract = {Krill are shrimp-like crustaceans with a high degree of mobility and variety of documented swimming behaviors. The caridoid escape response, a fast-start mechanism unique to crustaceans, occurs when the animal performs a series of rapid abdominal flexions and tail flipping that results in powerful backward strokes. The current results quantify the animal kinematics and three-dimensional flow field around a free-swimming Euphausia superba as it performs the caridoid escape maneuver. The specimen performs a single abdominal flexion-tail flip combination that leads to an acceleration over a 42 ms interval allowing it to reach a maximum speed of 57.0 cm/s (17.3 body lengths/s). The krill's tail flipping during the abdominal closure is a significant contributor to the thrust generation during the maneuver. The krill sheds a complex chain of vortex rings in its wake due to the viscous flow effects while the organism accelerates. The vortex ring structure reveals a strong suction flow in the wake, which suggests that the pressure distribution and form drag play a role in the force balance for this maneuver. Antarctic krill typically swim in a low to intermediate Reynolds number (Re) regime where viscous forces are significant, but as shown by this analysis, its high maneuverability allows it to quickly change its body angle and swimming speed.}, } @article {pmid37004257, year = {2023}, author = {Ozawa, K and Nakamura, H and Shimamura, K and Dietze, GF and Yoshikawa, HN and Zoueshtiagh, F and Kurose, K and Mu, L and Ueno, I}, title = {Capillary-driven horseshoe vortex forming around a micro-pillar.}, journal = {Journal of colloid and interface science}, volume = {642}, number = {}, pages = {227-234}, doi = {10.1016/j.jcis.2023.03.039}, pmid = {37004257}, issn = {1095-7103}, abstract = {HYPOTHESIS: Horseshoe vortices are known to emerge around large-scale obstacles, such as bridge pillars, due to an inertia-driven adverse pressure gradient forming on the upstream-side of the obstacle. We contend that a similar flow structure can arise in thin-film Stokes flow around micro-obstacles, such as used in textured surfaces to improve wettability. This could be exploited to enhance mixing in microfluidic devices, typically limited to creeping-flow regimes.

EXPERIMENTS: Numerical simulations based on the Navier-Stokes equations are carried out to elucidate the flow structure associated with the wetting dynamics of a liquid film spreading around a 50 μm diameter micro-pillar. The employed multiphase solver, which is based on the volume of fluid method, accurately reproduces the wetting dynamics observed in current and previous (Mu et al., Langmuir, 2019) experiments.

FINDINGS: The flow structure within the liquid meniscus forming at the foot of the micro-pillar evinces a horseshoe vortex wrapping around the obstacle, notwithstanding that the Reynolds number in our system is extremely low. Here, the adverse pressure gradient driving flow reversal near the bounding wall is caused by capillarity instead of inertia. The horseshoe vortex is entangled with other vortical structures, leading to an intricate flow system with high-potential mixing capabilities.}, } @article {pmid36997565, year = {2023}, author = {Monti, A and Olivieri, S and Rosti, ME}, title = {Collective dynamics of dense hairy surfaces in turbulent flow.}, journal = {Scientific reports}, volume = {13}, number = {1}, pages = {5184}, pmid = {36997565}, issn = {2045-2322}, abstract = {Flexible filamentous beds interacting with a turbulent flow represent a fundamental setting for many environmental phenomena, e.g., aquatic canopies in marine current. Exploiting direct numerical simulations at high Reynolds number where the canopy stems are modelled individually, we provide evidence on the essential features of the honami/monami collective motion experienced by hairy surfaces over a range of different flexibilities, i.e., Cauchy number. Our findings clearly confirm that the collective motion is essentially driven by fluid flow turbulence, with the canopy having in this respect a fully-passive behavior. Instead, some features pertaining to the structural response turn out to manifest in the motion of the individual canopy elements when focusing, in particular, on the spanwise oscillation and/or on sufficiently small Cauchy numbers.}, } @article {pmid36984947, year = {2023}, author = {Lei, Y and Wang, J and Li, Y and Gao, Q}, title = {In-Hover Aerodynamic Analysis of a Small Rotor with a Thin Circular-Arc Airfoil and a Convex Structure at Low Reynolds Number.}, journal = {Micromachines}, volume = {14}, number = {3}, pages = {}, pmid = {36984947}, issn = {2072-666X}, support = {52275095//National Natural Science Foundation of China/ ; 20200201294JC//Science and Technology Development Plan Project of Jilin Province/ ; }, abstract = {This study focused on the in-hover aerodynamics of a small rotor with a thin circular-arc airfoil and a convex structure at a low Reynolds number. The method combined computational fluid dynamics (CFD) with the blade element momentum theory (BEMT). The former was used for studying the two-dimensional parametric aerodynamics of the airfoil at a low Reynolds number and the latter was used for the prediction of the rotor's hover performance. A novel thin circular-arc airfoil with a convex structure with a high aerodynamic performance, high structural strength, light weight and easy manufacturing process is presented in this paper. A convex curve on the upper surface was adopted to increase the thickness of the airfoil at partial chord, and a stiffener in the airfoil was installed to improve the structural strength of rotor span-wise. The aerodynamic performance of the airfoil was numerically simulated by the two-dimensional steady and incompressible Navier-Stokes equations. The in-hover performance of the rotor for small-scale vehicles was predicted by an improved version of the blade element momentum theory (BEMT). Finally, a carbon-fiber rotor with the presented airfoil was manufactured that had a diameter of 40 cm and a pitch of 6.2 inches. The analysis results were verified by experiments. It was shown that the maximum calculation errors were below 6%. The improved BEMT can be used in the analysis of in-hover micro-rotor aerodynamics at low Reynolds numbers.}, } @article {pmid36984677, year = {2023}, author = {Park, JE and Kang, TG and Moon, H}, title = {The Effect of the Rotating Disk Geometry on the Flow and Flux Enhancement in a Dynamic Filtration System.}, journal = {Membranes}, volume = {13}, number = {3}, pages = {}, pmid = {36984677}, issn = {2077-0375}, support = {2022R1A2C1007886//National Research Foundation of Korea/ ; 2019 Faculty Research grant//Korea Aerospace University/ ; }, abstract = {A numerical study was conducted to investigate the effect of rotating patterned disks on the flow and permeate flux in a dynamic filtration (DF) system. The DF system consists of a rotating patterned disk and a stationary housing with a circular flat membrane. The feed flow is driven by the rotating disk with the angular velocity ranging from 200 to 1000 rpm and the applied pressure difference between inlet and outlet ports. Wheel-shaped patterns are engraved on the disk surfaces to add perturbation to the flow field and improve the permeate flux in the filtration system. Five disks with varying numbers of patterns were used in numerical simulations to examine the effects of the number of patterns and the angular velocity of the disk on the flow and permeate flux in the DF system. The flow characteristics are studied using the velocity profiles, the cross-sectional velocity vectors, the vortex structures, and the shear stress distribution. The wheel-shaped patterns shift the central core layer in the circumferential velocity profile towards the membrane, leading to higher shear stresses at the membrane and higher flux compared to a plain disk. When the number of patterns on the disk exceeded eight at a fixed Reynolds number, there were significant increases in wall shear stress and permeate flux compared to a plain disk filtration system with no pattern.}, } @article {pmid36967929, year = {2023}, author = {Sakib, MN and Shuvo, MS and Rahman, R and Saha, S}, title = {Particle deposition and fluid flow characteristics in turbulent corrugated pipe flow using Eulerian-Lagrangian approach.}, journal = {Heliyon}, volume = {9}, number = {3}, pages = {e14603}, pmid = {36967929}, issn = {2405-8440}, abstract = {A numerical simulation of aerosol particle deposition in a horizontal circular pipe with a corrugated wall under turbulent flow has been carried out in this research. This paper uses the RNG k-ε turbulence model with Enhanced Wall Treatment to simulate fluid flow. Furthermore, the Lagrangian particle tracking model simulates particle deposition in the corrugated pipe. Air-particle interaction is influenced by Stokes number, surface roughness, flow velocity, particle diameter, and pipe diameter. For the parametric simulation, particle diameter varies from 1 to 30 μm, whereas the Reynolds number ranges from 5000 to 10,000. The effect of corrugation height and pipe diameter on deposition efficiency is also investigated. This study shows that corrugation height significantly increases particle deposition compared to the smooth wall pipe. As the pipe diameter decreases, keeping the corrugation ratio constant, deposition efficiency also increases. Moreover, high flow velocity enhances deposition efficiency for particle diameters lower than 5 μm.}, } @article {pmid36966222, year = {2023}, author = {Memon, AA and Memon, MA and Fenta, A}, title = {A laminar forced convection via transport of water-copper-aluminum hybrid nanofluid through heated deep and shallow cavity with Corcione model.}, journal = {Scientific reports}, volume = {13}, number = {1}, pages = {4915}, pmid = {36966222}, issn = {2045-2322}, abstract = {The article explores how fluid flows and heat transfers in both deep and shallow cavities when using a nanofluid made of water, copper, and aluminum oxide. The study applies the Corcione model to hybrid nanofluids, which considers viscosity, conductivity, and the size of the nanoparticle, temperature, and Reynolds number. The cavity is connected to a rectangular channel, with the cavity's length being half the total length of the enclosure, and the aspect ratio (cavity height divided by height of the channel) is tested from 1 to 3. The study uses the Navier-Stokes equation and energy equation in two dimensions, along with finite element-based software, COMSOL 5.6, to simulate the combination of fluid flow and heat transmission. The results show a circular distribution of temperature in the cavity, and the average temperature drops as the volume fraction of copper upsurges. However, both the Reynolds number and volume fraction of copper improve the average Nusselt number, which shows how well the fluid transfers heat, along the cavity's middle line. The percentage change in the average Nusselt number decreases as the aspect ratio increases, indicating improved conduction.}, } @article {pmid36959904, year = {2023}, author = {Xiong, J and Zhang, J and Zhong, Y and Song, X and Wang, H and Cheang, UK}, title = {Magnetically-actuated hydrogel-based achiral planar microswimmers for SERS detection: In situ coprecipitation for continuous loading of iron oxide nanoparticles.}, journal = {Frontiers in bioengineering and biotechnology}, volume = {11}, number = {}, pages = {1086106}, pmid = {36959904}, issn = {2296-4185}, abstract = {Ultraviolet lithography is a very promising technology used for the batch fabrication of biomedical microswimmers. However, creating microswimmers that can swim at low Reynolds number using biocompatible materials while retaining strong magnetic properties and excellent biomedical functionality is a great challenge. Most of the previously reported biomedical microswimmers possess either strong magnetic properties by using non-biocompatible nickel coating or good biocompatibility by using iron oxide particle-embedded hydrogel with weak magnetism, but not both. Alternatively, iron oxide nanoparticles can be coated on the surface of microswimmers to improve magnetic properties; however, this method limited the usability of the microswimmers' surfaces. To address these shortcomings, this work utilized an in situ synthesis technique to generate high magnetic content inside hydrogel-based achiral planar microswimmers while leaving their surfaces free to be functionalized for SERS detection. The hydrogel matrices of the magnetically actuated hydrogel-based microswimmers were first prepared by ultraviolet lithography. Then, the high concentration of iron oxide was achieved through multiple continuous in situ coprecipitation cycles. Finally, the SERS detection capability of magnetically actuated hydrogel-based microswimmers was enabled by uniformly growing silver nanoparticles on the surface of the microswimmers. In the motion control tests, the microswimmers showed a high swimming efficiency, high step-out frequency, and consistent synchronized motion. Furthermore, the magnetically actuated hydrogel-based microswimmers were able to improve the detection efficiency of analytes under magnetic guidance.}, } @article {pmid36951265, year = {2023}, author = {Liu, D and Chen, S and Luo, X}, title = {Influence factors of channel geometry for separation of circulating tumor cells by four-ring inertial focusing microchannel.}, journal = {Cell biochemistry and function}, volume = {41}, number = {3}, pages = {375-388}, doi = {10.1002/cbf.3791}, pmid = {36951265}, issn = {1099-0844}, support = {52165046//National Natural Science Foundation of China/ ; }, mesh = {Humans ; *Microfluidic Analytical Techniques/methods ; *Neoplastic Cells, Circulating ; Microfluidics/methods ; MCF-7 Cells ; Cell Line, Tumor ; Cell Separation/methods ; }, abstract = {Inertial microfluidics is a high-throughput and high-efficiency cell separation approach to which attention has been progressively paid in recent years. However, research on the influencing factors that compromise the efficiency of cell separation is still lacking. Therefore, the aim of this study was to evaluate the cell separation efficiency by changing the influencing factors. A four-ring inertial focusing spiral microchannel was designed to separate two kinds of circulating tumor cells (CTCs) from blood. Human breast cancer (MCF-7) cells and human epithelial cervical cancer (HeLa) cells enter the four-ring inertial focusing spiral microchannel together with blood cells, and cancer cells and blood cells were separated from each other at the outlet of the channel by inertial force. The cell separation efficiency at the inlet flow rate in the Reynolds number range of 40-52 was studied by changing the influencing factors such as the cross-sectional shape of the microchannel, the average thickness of the cross-section, and the trapezoidal inclination angle. The results showed that the reduction of the channel thickness and the increase of a certain trapezoidal inclination enhanced the cell separation efficiency to a certain extent, the study showed that when the channel inclination was 6 ° and the average channel thickness was 160 μm. The two kinds of CTC cells could be completely separated from the blood and the efficiency could reached 100%.}, } @article {pmid36938115, year = {2023}, author = {Kitzinger, E and Leclercq, T and Marquet, O and Piot, E and Sipp, D}, title = {Attachment-line, crossflow and Tollmien-Schlichting instabilities on swept ONERA-D and Joukowski airfoils.}, journal = {Journal of fluid mechanics}, volume = {957}, number = {}, pages = {}, doi = {10.1017/jfm.2023.38}, pmid = {36938115}, issn = {0022-1120}, abstract = {Linear stability analyses are performed to investigate the boundary layer instabilities developing in an incompressible flow around the whole leading-edge of swept ONERA-D and Joukowski airfoils of infinite span. The stability analyses conducted in our study are global in the chordwise direction and local in the spanwise direction. A neutral curve is drawn at a given leading-edge Reynolds number ReR and several overlapping regions, called "lobes", are identified on a physical basis. A detailed study of the marginal modes reveals the presence of attachment-line and crossflow instabilities, as well as modes whose features do not fall within the standards of a specific type. Connected crossflow/Tollmien-Schlichting modes, that show a dominant spatial structure reminiscent of Tollmien-Schlichting waves but whose destabilization is linked to a crossflow mechanism, have been identified. The comparison of several neutral curves at different ReR values reveals the greater stabilizing effect of the increase of ReR on the crossflow instability compared to the attachment-line instability. The influence of the airfoil shape is also studied by comparing the neutral curves of the ONERA-D with the neutral curves of the Joukowski airfoil. These curves reveal similar characteristics with the presence of distinct lobes and their comparison at constant sweep angle shows that, under the conditions studied, the ONERA-D airfoil is more stable than the Joukowski airfoil, even for crossflow instabilities. The absolutely or convectively unstable nature of the flow in the spanwise direction is also tackled and our results suggest that the flow is only convectively unstable.}, } @article {pmid36936325, year = {2023}, author = {Rehman, S and Hashim, and Hassine, SBH and Tag Eldin, E and Shah, SO}, title = {Investigation of Entropy Production with Thermal Analysis under Soret and Dufour Effects in MHD Flow between Convergent and Divergent Channels.}, journal = {ACS omega}, volume = {8}, number = {10}, pages = {9121-9136}, pmid = {36936325}, issn = {2470-1343}, abstract = {Hydromagnetic flow and heat transport have sustainable importance in conventional system design along with high-performance thermal equipment and geothermal energy structures. The current computational study investigates the energy transport and entropy production due to the pressure-driven flow of non-Newtonian fluid filled inside the wedge-shaped channel. The nonlinear radiation flux and uniform magnetic field are incorporated into the flow analysis. To be more precise, non-Newtonian fluid initiates from an inlet with the bound of the parabolic profile and leaves at outlet of a convergent/divergent channel. We assume that the channel flow is adiabatic and influenced by the wall friction. The leading flow equations are modeled via the Carreau fluid model using fundamental conservation laws. The thermodynamical aspect of the system is visualized using a two-phase model and analyses of the entropy equation due to fluid friction, ohmic heating, and diffusion of heat and mass fluxes. The modeled system of equations is normalized using a dimensionless variable mechanism. The system was elevated for the significant variation of controlling parameters. The outcomes obtained from the computational investigation are validated with the theoretical results that are available in the literature. An increasing semivertex angle and Reynolds number increase the converging channel flow. In the core flow zone, an increase in the divergent semiangle causes the flow to decelerate, while near and at the channel wall it causes a slight acceleration. Outcomes designate that the main contribution to the irreversibility is due to ohmic loss, frictional loss, and heat loss. The thermal performance and entropy production is dominant for a diverging flow. The outcomes of this research will assist in comprehending the process of entropy minimization in conjunction with the flow of nanomaterials in a nonuniform channel, which is essential in engineering processes such as the creation of micro machines, supersonic Jets, nozzles, and clean energy.}, } @article {pmid36932601, year = {2023}, author = {Fan, Y and Cadot, O}, title = {Reynolds number effect on the bistable dynamic of a blunt-base bluff body.}, journal = {Physical review. E}, volume = {107}, number = {2-2}, pages = {025103}, doi = {10.1103/PhysRevE.107.025103}, pmid = {36932601}, issn = {2470-0053}, abstract = {A three-dimensional blunt-base bluff body in a uniform flow is subjected to long-time stochastic dynamics of switching between two opposite wake states. This dynamic is investigated experimentally within the Reynolds number range Re ≃10^{4}-10^{5}. Long-time statistics coupled to a sensitivity analysis to the body attitude (defined as the pitch angle of the body with respect to the incoming flow) show that the wake switching rate decreases as Re increases. Equipping the body with passive roughness elements (turbulators) modifies the boundary layers before separation, seen as the inlet condition for the wake dynamic. Depending on their location and Re, the viscous sublayer length scale and the turbulent layer thickness can be modified independently. This sensitivity analysis to the inlet condition shows that a decrease of the viscous sublayer length scale at a given turbulent layer thickness leads to a decrease in the switching rate, whereas the modification of the turbulent layer thickness has almost no effect on the switching rate.}, } @article {pmid36932550, year = {2023}, author = {Ginzburg, I and Silva, G and Marson, F and Chopard, B and Latt, J}, title = {Unified directional parabolic-accurate lattice Boltzmann boundary schemes for grid-rotated narrow gaps and curved walls in creeping and inertial fluid flows.}, journal = {Physical review. E}, volume = {107}, number = {2-2}, pages = {025303}, doi = {10.1103/PhysRevE.107.025303}, pmid = {36932550}, issn = {2470-0053}, abstract = {The goal of this work is to advance the characteristics of existing lattice Boltzmann Dirichlet velocity boundary schemes in terms of the accuracy, locality, stability, and mass conservation for arbitrarily grid-inclined straight walls, curved surfaces, and narrow fluid gaps, for both creeping and inertial flow regimes. We reach this objective with two infinite-member boundary classes: (1) the single-node "Linear Plus" (LI^{+}) and (2) the two-node "Extended Multireflection" (EMR). The LI^{+} unifies all directional rules relying on the linear combinations of up to three pre- or postcollision populations, including their "ghost-node" interpolations and adjustable nonequilibrium approximations. On this basis, we propose three groups of LI^{+} nonequilibrium local corrections: (1) the LI_{1}^{+} is parametrized, meaning that its steady-state solution is physically consistent: the momentum accuracy is viscosity-independent in Stokes flow, and it is fixed by the Reynolds number (Re) in inertial flow; (2) the LI_{3}^{+} is parametrized, exact for arbitrary grid-rotated Poiseuille force-driven Stokes flow and thus most accurate in porous flow; and (3) the LI_{4}^{+} is parametrized, exact for pressure and inertial term gradients, and hence advantageous in very narrow porous gaps and at higher Reynolds range. The directional, two-relaxation-time collision operator plays a crucial role for all these features, but also for efficiency and robustness of the boundary schemes due to a proposed nonequilibrium linear stability criterion which reliably delineates their suitable coefficients and relaxation space. Our methodology allows one to improve any directional rule for Stokes or Navier-Stokes accuracy, but their parametrization is not guaranteed. In this context, the parametrized two-node EMR class enlarges the single-node schemes to match exactness in a grid-rotated linear Couette flow modeled with an equilibrium distribution designed for the Navier-Stokes equation (NSE). However, exactness of a grid-rotated Poiseuille NSE flow requires us to perform (1) the modification of the standard NSE term for exact bulk solvability and (2) the EMR extension towards the third neighbor node. A unique relaxation and equilibrium exact configuration for grid-rotated Poiseuille NSE flow allows us to classify the Galilean invariance characteristics of the boundary schemes without any bulk interference; in turn, its truncated solution suggests how, when increasing the Reynolds number, to avoid a deterioration of the mass-leakage rate and momentum accuracy due to a specific Reynolds scaling of the kinetic relaxation collision rate. The optimal schemes and strategies for creeping and inertial regimes are then singled out through a series of numerical tests, such as grid-rotated channels and rotated Couette flow with wall-normal injection, cylindrical porous array, and Couette flow between concentric cylinders, also comparing them against circular-shape fitted FEM solutions.}, } @article {pmid36930713, year = {2023}, author = {Hu, T and Wang, H and Gomez, H}, title = {Direct van der Waals simulation (DVS) of phase-transforming fluids.}, journal = {Science advances}, volume = {9}, number = {11}, pages = {eadg3007}, pmid = {36930713}, issn = {2375-2548}, abstract = {We present the method of direct van der Waals simulation (DVS) to study computationally flows with liquid-vapor phase transformations. Our approach is based on a discretization of the Navier-Stokes-Korteweg equations, which couple flow dynamics with van der Waals' nonequilibrium thermodynamic theory of phase transformations, and opens an opportunity for first-principles simulation of a wide range of boiling and cavitating flows. The proposed algorithm enables unprecedented simulations of the Navier-Stokes-Korteweg equations involving cavitating flows at strongly under-critical conditions and 𝒪(10[5]) Reynolds number. The proposed technique provides a pathway for a fundamental understanding of phase-transforming flows with multiple applications in science, engineering, and medicine.}, } @article {pmid36929245, year = {2023}, author = {Sheikhshoaei, A and Rajabi, M}, title = {Utilizing passive elements to break time reversibility at low Reynolds number: a swimmer with one activated element.}, journal = {The European physical journal. E, Soft matter}, volume = {46}, number = {3}, pages = {15}, pmid = {36929245}, issn = {1292-895X}, abstract = {In the realm of low Reynolds number, the shape-changing biological and artificial matters need to break time reversibility in the course of their strokes to achieve motility. This necessity is well described in the so-called scallop theorem. In this work, considering low Reynolds number, a novel and versatile swimmer is proposed as an example of a new scheme to break time reversibility kinematically and, in turn, produce net motion. The swimmer consists of one sphere as a cargo or carried body, joined by one activated link with time-varying length, to another perpendicular rigid link, as the support of two passively flapping disks, at its end. The disks are free to rotate between their fixed minimum and maximum angles. The system's motion in two dimensions is simulated, and the maneuverability of the swimmer is discussed. The minimal operating parameters for steering of the swimmer are studied, and the limits of the swimmer are identified. The introduced swimming mechanism can be employed as a simple model system for biological living matters as well as artificial microswimmers.}, } @article {pmid36920868, year = {2023}, author = {Spatafora-Salazar, A and Kuei, S and Cunha, LHP and Biswal, SL}, title = {Coiling of semiflexible paramagnetic colloidal chains.}, journal = {Soft matter}, volume = {19}, number = {13}, pages = {2385-2396}, doi = {10.1039/d3sm00066d}, pmid = {36920868}, issn = {1744-6848}, abstract = {Semiflexible filaments deform into a variety of configurations that dictate different phenomena manifesting at low Reynolds number. Harnessing the elasticity of these filaments to perform transport-related processes at the microfluidic scale requires structures that can be directly manipulated to attain controllable geometric features during their deformation. The configuration of semiflexible chains assembled from paramagnetic colloids can be readily controlled upon the application of external time-varying magnetic fields. In circularly rotating magnetic fields, these chains undergo coiling dynamics in which their ends close into loops that wrap inward, analogous to the curling of long nylon filaments under shear. The coiling is promising for the precise loading and targeted transport of small materials, however effective implementation requires an understanding of the role that field parameters and chain properties play on the coiling features. Here, we investigate the formation of coils in semiflexible paramagnetic chains using numerical simulations. We demonstrate that the size and shape of the initial coils are governed by the Mason and elastoviscous numbers, related to the field parameters and the chain bending stiffness. The size of the initial coil follows a nonmonotonic behavior with Mason number from which two regions are identified: (1) an elasticity-dependent nonlinear regime in which the coil size decreases with increasing field strength and for which loop shape tends to be circular, and (2) an elasticity-independent linear regime where the size increases with field strength and the shape become more elliptical. From the time scales associated to these regimes, we identify distinct coiling mechanisms for each case that relate the coiling dynamics to two other configurational dynamics of paramagnetic chains: wagging and folding behaviors.}, } @article {pmid36916641, year = {2023}, author = {Lim, S and Yadunandan, A and Khalid Jawed, M}, title = {Bacteria-inspired robotic propulsion from bundling of soft helical filaments at low Reynolds number.}, journal = {Soft matter}, volume = {19}, number = {12}, pages = {2254-2264}, doi = {10.1039/d2sm01398c}, pmid = {36916641}, issn = {1744-6848}, abstract = {The bundling of flagella is known to create a "run" phase, where the bacteria moves in a nearly straight line rather than making changes in direction. Historically, mechanical explanations for the bundling phenomenon intrigued many researchers, and significant advances were made in physical models and experimental methods. Contributing to the field of research, we present a bacteria-inspired centimeter-scale soft robotic hardware platform and a computational framework for a physically plausible simulation model of the multi-flagellated robot under low Reynolds number (∼10[-1]). The fluid-structure interaction simulation couples the discrete elastic rods algorithm with the method of regularized Stokeslet segments. Contact between two flagella is handled by a penalty-based method. We present a comparison between our experimental and simulation results and verify that the simulation tool can capture the essential physics of this problem. Preliminary findings on robustness to buckling provided by the bundling phenomenon and the efficiency of a multi-flagellated soft robot are compared with the single-flagellated counterparts. Observations were made on the coupling between geometry and elasticity, which manifests itself in the propulsion of the robot by nonlinear dependency on the rotational speed of the flagella.}, } @article {pmid36907215, year = {2023}, author = {Kang, C and Mirbod, P}, title = {Transitions in Taylor-Couette flow of concentrated non-colloidal suspensions.}, journal = {Philosophical transactions. Series A, Mathematical, physical, and engineering sciences}, volume = {381}, number = {2246}, pages = {20220126}, doi = {10.1098/rsta.2022.0126}, pmid = {36907215}, issn = {1471-2962}, abstract = {Taylor-Couette flow of concentrated non-colloidal suspensions with a rotating inner cylinder and a stationary outer one is numerically investigated. We consider suspensions of the bulk particle volume fraction ϕb = 0.2, 0.3 with the ratio of annular gap to the particle radius ε = 60 confined in a cylindrical annulus of the radius ratio (i.e. ratio of inner and outer radii) η = 0.877. Numerical simulations are performed by applying suspension-balance model and rheological constitutive laws. To observe flow patterns caused by suspended particles, the Reynolds number of the suspension, based on the bulk particle volume fraction and the rotating velocity of the inner cylinder, is varied up to 180. At high Reynolds number, modulated patterns undiscovered in the flow of a semi-dilute suspension emerge beyond a wavy vortex flow. Thus, a transition occurs from the circular Couette flow via ribbons, spiral vortex flow, wavy spiral vortex flow, wavy vortex flow and modulated wavy vortex flow for the concentrated suspensions. Moreover, friction and torque coefficients for suspensions are estimated. It turns out that suspended particles significantly enhance the torque on the inner cylinder while reducing friction coefficient and the pseudo-Nusselt number. In particular, the coefficients are reduced in the flow of more dense suspensions. This article is part of the theme issue 'Taylor-Couette and related flows on the centennial of Taylor's seminal Philosophical Transactions paper (Part 2)'.}, } @article {pmid36907213, year = {2023}, author = {Nagata, M}, title = {Taylor-Couette flow in the narrow-gap limit.}, journal = {Philosophical transactions. Series A, Mathematical, physical, and engineering sciences}, volume = {381}, number = {2246}, pages = {20220134}, doi = {10.1098/rsta.2022.0134}, pmid = {36907213}, issn = {1471-2962}, abstract = {A Cartesian representation of the Taylor-Couette system in the vanishing limit of the gap between coaxial cylinders is presented, where the ratio, [Formula: see text], of the angular velocities, [Formula: see text] and [Formula: see text], of the inner and the outer cylinders, respectively, affects its axisymmetric flow structures. Our numerical stability study finds remarkable agreement with previous studies for the critical Taylor number, [Formula: see text], for the onset of axisymmetric instability. The Taylor number [Formula: see text] can be expressed as [Formula: see text], where [Formula: see text] (the rotation number) and [Formula: see text] (the Reynolds number) in the Cartesian system are related to the average and the difference of [Formula: see text] and [Formula: see text]. The instability sets in the region [Formula: see text], while the product of [Formula: see text] and [Formula: see text] is kept finite. Furthermore, we developed a numerical code to calculate nonlinear axisymmetric flows. It is found that the mean flow distortion of the axisymmetric flow is antisymmetric across the gap when [Formula: see text], while a symmetric part of the mean flow distortion appears additionally when [Formula: see text]. Our analysis also shows that for a finite [Formula: see text] all flows with [Formula: see text] approach the [Formula: see text] axis, so that the plane Couette flow system is recovered in the vanishing gap limit. This article is part of the theme issue 'Taylor-Couette and related flows on the centennial of Taylor's seminal Philosophical Transactions paper (Part 2)'.}, } @article {pmid36907211, year = {2023}, author = {Moazzen, M and Lacassagne, T and Thomy, V and Bahrani, SA}, title = {Friction dynamics of elasto-inertial turbulence in Taylor-Couette flow of viscoelastic fluids.}, journal = {Philosophical transactions. Series A, Mathematical, physical, and engineering sciences}, volume = {381}, number = {2246}, pages = {20220300}, doi = {10.1098/rsta.2022.0300}, pmid = {36907211}, issn = {1471-2962}, abstract = {Dynamic properties of elasto-inertial turbulence (EIT) are studied in a Taylor-Couette geometry. EIT is a chaotic flow state that develops upon both non-negligible inertia and viscoelasticity. A combination of direct flow visualization and torque measurement allows to verify the earlier onset of EIT compared with purely inertial instabilities (and inertial turbulence). The scaling of the pseudo-Nusselt number with inertia and elasticity is discussed here for the first time. Variations in the friction coefficient, temporal frequency spectra and spatial power density spectra highlight that EIT undergoes an intermediate behaviour before transitioning to its fully developed chaotic state that requires both high inertia and elasticity. During this transition, the contribution of secondary flows to the overall friction dynamics is limited. This is expected to be of great interest in the aim of achieving efficiency mixing at low drag and low but finite Reynolds number. This article is part of the theme issue "Taylor-Couette and related flows on the centennial of Taylor's seminal Philosophical transactions paper (Part 2)".}, } @article {pmid36907210, year = {2023}, author = {Krivonosova, O and Gritsevich, M and Zhilenko, D and Read, P}, title = {Noise induced effects in the axisymmetric spherical Couette flow.}, journal = {Philosophical transactions. Series A, Mathematical, physical, and engineering sciences}, volume = {381}, number = {2246}, pages = {20220124}, doi = {10.1098/rsta.2022.0124}, pmid = {36907210}, issn = {1471-2962}, abstract = {We study the axisymmetric, wide gap, spherical Couette flow in the presence of noise in numerical simulations and experiments. Such studies are important because most of the flows in nature are subjected to random fluctuations. Noise is introduced into the flow by adding fluctuations to the inner sphere rotation which are random in time with zero mean. Flows of a viscous incompressible fluid are induced either by rotation of the inner sphere only or by the co-rotation of the spheres. Mean flow generation was found to occur under the action of additive noise. A higher relative amplification of meridional kinetic energy compared to the azimuthal component was also observed under certain conditions. Calculated flow velocities were validated by laser Doppler anemometer measurements. A model is proposed to elucidate the rapid growth of meridional kinetic energy for flows induced by varying the co-rotation of the spheres. Our linear stability analysis for flows induced by the rotation of the inner sphere revealed a decrease in the critical Reynolds number, corresponding to the onset of the first instability. Also, in this case, a local minimum of the mean flow generation on approaching the critical Reynolds number was observed, which is consistent with the available theoretical predictions. This article is part of the theme issue 'Taylor-Couette and related flows on the centennial of Taylor's seminal Philosophical Transactions paper (Part 2)'.}, } @article {pmid36903819, year = {2023}, author = {Akram, S and Athar, M and Saeed, K and Razia, A and Muhammad, T and Alghamdi, HA}, title = {Mechanism of Double-Diffusive Convection on Peristaltic Transport of Thermally Radiative Williamson Nanomaterials with Slip Boundaries and Induced Magnetic Field: A Bio-Nanoengineering Model.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {13}, number = {5}, pages = {}, pmid = {36903819}, issn = {2079-4991}, abstract = {The present work has mathematically modeled the peristaltic flow in nanofluid by using thermal radiation, induced a magnetic field, double-diffusive convection, and slip boundary conditions in an asymmetric channel. Peristalsis propagates the flow in an asymmetric channel. Using the linear mathematical link, the rheological equations are translated from fixed to wave frames. Next, the rheological equations are converted to nondimensional forms with the help of dimensionless variables. Further, the flow evaluation is determined under two scientific assumptions: a finite Reynolds number and a long wavelength. Mathematica software is used to solve the numerical value of rheological equations. Lastly, the impact of prominent hydromechanical parameters on trapping, velocity, concentration, magnetic force function, nanoparticle volume fraction, temperature, pressure gradient, and pressure rise are evaluated graphically.}, } @article {pmid36902954, year = {2023}, author = {Liu, C and Wang, W and Hu, X and Liu, F}, title = {Drag Reduction Technology of Water Flow on Microstructured Surfaces: A Novel Perspective from Vortex Distributions and Densities.}, journal = {Materials (Basel, Switzerland)}, volume = {16}, number = {5}, pages = {}, pmid = {36902954}, issn = {1996-1944}, support = {52079113//National Natural Science Foundation of China/ ; U2243235//Key project of National Natural Science Foundation of China/ ; }, abstract = {Revealing the turbulent drag reduction mechanism of water flow on microstructured surfaces is beneficial to controlling and using this technology to reduce turbulence losses and save energy during water transportation. Two microstructured samples, including a superhydrophobic and a riblet surface, were fabricated near which the water flow velocity, and the Reynolds shear stress and vortex distribution were investigated using a particle image velocimetry. The dimensionless velocity was introduced to simplify the Ω vortex method. The definition of vortex density in water flow was proposed to quantify the distribution of different strength vortices. Results showed that the velocity of the superhydrophobic surface (SHS) was higher compared with the riblet surface (RS), while the Reynolds shear stress was small. The vortices on microstructured surfaces were weakened within 0.2 times that of water depth when identified by the improved ΩM method. Meanwhile, the vortex density of weak vortices on microstructured surfaces increased, while the vortex density of strong vortices decreased, proving that the reduction mechanism of turbulence resistance on microstructured surfaces was to suppress the development of vortices. When the Reynolds number ranged from 85,900 to 137,440, the drag reduction impact of the superhydrophobic surface was the best, and the drag reduction rate was 9.48%. The reduction mechanism of turbulence resistance on microstructured surfaces was revealed from a novel perspective of vortex distributions and densities. Research on the structure of water flow near the microstructured surface can promote the drag reduction application in the water field.}, } @article {pmid36899067, year = {2023}, author = {Suresh Kumar, Y and Hussain, S and Raghunath, K and Ali, F and Guedri, K and Eldin, SM and Khan, MI}, title = {Numerical analysis of magnetohydrodynamics Casson nanofluid flow with activation energy, Hall current and thermal radiation.}, journal = {Scientific reports}, volume = {13}, number = {1}, pages = {4021}, pmid = {36899067}, issn = {2045-2322}, abstract = {In this study we analyzed the flow, heat and mass transfer behavior of Casson nanofluid past an exponentially stretching surface under the impact of activation energy, Hall current, thermal radiation, heat source/sink, Brownian motion and thermophoresis. Transverse magnetic field with the assumption of small Reynolds number is implemented vertically. The governing partial nonlinear differential equations of the flow, heat and mass transfer are transformed into ordinary differential equations by using similarity transformation and solved numerically by using Matlab bvp4c package. The impact of each of the Hall current parameter, thermal radiation parameter, heat source/sink parameter, Brownian motion parameter, Prandtl number, thermophoresis parameter and magnetic parameter on velocity, concentration and temperature, is discussed through graphs. The skin friction coefficient along the x-and z-directions, the local Nusselt number and the Sherwood number are calculated numerically to look into the inside behavior of the emerging parameters. It is witnessed that the flow velocity is a diminishing function of the thermal radiation parameter and the behavior has observed in the case of Hall parameter. Moreover, mounting values of Brownian motion parameter reduce the nanoparticle concentration profile.}, } @article {pmid36897856, year = {2023}, author = {Bae, AJ and Ahmad, R and Bodenschatz, E and Pumir, A and Gholami, A}, title = {Flagellum-driven cargoes: Influence of cargo size and the flagellum-cargo attachment geometry.}, journal = {PloS one}, volume = {18}, number = {3}, pages = {e0279940}, pmid = {36897856}, issn = {1932-6203}, mesh = {*Flagella ; Cilia ; *Chlamydomonas reinhardtii ; Mechanical Phenomena ; Calcium, Dietary ; }, abstract = {The beating of cilia and flagella, which relies on an efficient conversion of energy from ATP-hydrolysis into mechanical work, offers a promising way to propel synthetic cargoes. Recent experimental realizations of such micro-swimmers, in which micron-sized beads are propelled by isolated and demembranated flagella from the green algae Chlamydomonas reinhardtii (C. reinhardtii), revealed a variety of propulsion modes, depending in particular on the calcium concentration. Here, we investigate theoretically and numerically the propulsion of a bead as a function of the flagellar waveform and the attachment geometries between the bead and the flagellum. To this end, we take advantage of the low Reynolds number of the fluid flows generated by the micro-swimmer, which allows us to neglect fluid inertia. By describing the flagellar waveform as a superposition of a static component and a propagating wave, and using resistive-force theory, we show that the asymmetric sideways attachment of the flagellum to the bead makes a contribution to the rotational velocity of the micro-swimmer that is comparable to the contribution caused by the static component of the flagellar waveform. Remarkably, our analysis reveals the existence of a counter-intuitive propulsion regime in which an increase in the size of the cargo, and hence its drag, leads to an increase in some components of the velocity of the bead. Finally, we discuss the relevance of the uncovered mechanisms for the fabrication of synthetic, bio-actuated medical micro-robots for targeted drug delivery.}, } @article {pmid36895389, year = {2023}, author = {Lei, Y and Wang, X and Zhou, D and Qiu, T and Jin, W and Qin, C and Zhou, D}, title = {Experimental investigation on high-pressure methane jet characteristic single-hole injector.}, journal = {Heliyon}, volume = {9}, number = {3}, pages = {e13645}, doi = {10.1016/j.heliyon.2023.e13645}, pmid = {36895389}, issn = {2405-8440}, abstract = {High-pressure gas direct injection (DI) technology benefits engines with high efficiency and clean emissions, and the gas jet process causes crucial effects especially inside an mm-size space. This study presents an investigation on the high-pressure methane jet characteristics from a single-hole injector by analysing jet performance parameters including jet impact force, gas jet impulse, and jet mass flow rate. The results show that the methane jet exhibited a two-zone behaviour along the jet direction in the spatial dimension induced by high-speed jet flow from the nozzle: zone 1 near the nozzle-the jet impact force and jet impulse increased consistently except for a fluctuation due to shock wave effects induced by the sonic jet and no entrainment occurs, and zone II farther away from the nozzle-the jet impact force and jet impulse became stable when the shock wave effects became weak and the jet impulse was conserved with a linear conservation boundary. The Mach disk height was exactly the turning point of two zones. Moreover, the methane jet parameters, such as the methane jet mass flow rate, jet initial jet impact force, jet impulse, and Reynolds number had a monotonous and linearly increasing correlation with injection pressure.}, } @article {pmid36890189, year = {2023}, author = {Vieira, GS and Allshouse, MR and Mahadevan, A}, title = {Seagrass deformation affects fluid instability and tracer exchange in canopy flow.}, journal = {Scientific reports}, volume = {13}, number = {1}, pages = {3910}, pmid = {36890189}, issn = {2045-2322}, abstract = {Monami is the synchronous waving of a submerged seagrass bed in response to unidirectional fluid flow. Here we develop a multiphase model for the dynamical instabilities and flow-driven collective motions of buoyant, deformable seagrass. We show that the impedance to flow due to the seagrass results in an unstable velocity shear layer at the canopy interface, leading to a periodic array of vortices that propagate downstream. Our simplified model, configured for unidirectional flow in a channel, provides a better understanding of the interaction between these vortices and the seagrass bed. Each passing vortex locally weakens the along-stream velocity at the canopy top, reducing the drag and allowing the deformed grass to straighten up just beneath it. This causes the grass to oscillate periodically even in the absence of water waves. Crucially, the maximal grass deflection is out of phase with the vortices. A phase diagram for the onset of instability shows its dependence on the fluid Reynolds number and an effective buoyancy parameter. Less buoyant grass is more easily deformed by the flow and forms a weaker shear layer, with smaller vortices and less material exchange across the canopy top. While higher Reynolds number leads to stronger vortices and larger waving amplitudes of the seagrass, waving amplitude is maximized at intermediate grass buoyancy. All together, our theory and computations develop an updated schematic of the instability mechanism consistent with experimental observations.}, } @article {pmid36889000, year = {2023}, author = {Zhu, Q}, title = {Wall effect on the start maneuver of a jet swimmer.}, journal = {Bioinspiration & biomimetics}, volume = {18}, number = {3}, pages = {}, doi = {10.1088/1748-3190/acc293}, pmid = {36889000}, issn = {1748-3190}, mesh = {Animals ; Biomechanical Phenomena ; *Locomotion ; *Swimming ; Motion ; Decapodiformes ; }, abstract = {Inspired by aquatic creatures such as squid, the novel propulsion method based on pulsed jetting is a promising way to achieve high speed and high maneuverability. To study the potential application of this locomotion method in confined space with complicated boundary conditions, it is critical to understand their dynamics in the vicinity of solid boundaries. In this study we numerically examine the start maneuver of an idealized jet swimmer near a wall. Our simulations illustrate three important mechanisms: (1) due to the blocking effect of the wall the pressure inside the body is affected so that the forward acceleration is increased during deflation and decreased during inflation; (2) the wall affects the internal flow so that the momentum flux at the nozzle and subsequently the thrust generation during the jetting phase are slightly increased; (3) the wall affects the wake so that the refilling phase is influenced, leading to a scenario in which part of the energy expended during jetting is recovered during refilling to increase forward acceleration and reduce power expenditure. In general, the second mechanism is weaker than the other two. The exact effects of these mechanisms depend on physical parameters such as the initial phase of the body deformation, the distance between the swimming body and the wall, and the Reynolds number.}, } @article {pmid36888616, year = {2023}, author = {Gao, P and Wang, Q and Liu, T}, title = {Numerical method investigation on the aggregation characteristics of non-spherical particles.}, journal = {PloS one}, volume = {18}, number = {3}, pages = {e0282804}, pmid = {36888616}, issn = {1932-6203}, mesh = {*Microfluidics/methods ; Motion ; *Particulate Matter ; }, abstract = {Under the background of the mechanical mechanism research of microfluidic technology for separating and screening pipeline particulate matter, this paper proposes an improved relative motion model by combining the multiple reference frame method and the relative motion model. Worked with a quasi-fixed constant method, this model can numerically calculate the aggregation features of non-spherical particles in the low Reynolds number channels. The results demonstrate that when Re = 40~80, ellipsoids exhibit an aggregation trend similar to circular particles with the same diameter as its largest circumscribed sphere. The aggregation position is affected by the ratio of long and short axes of particles, and the distribution trend is determined by the relative size of these particles. When the channel's Reynolds number is less than the critical Reynolds number, the aggregation position of elliptical particles will be closer to the pipe center with the increase in the Reynolds number, which is contrary to the aggregation tendency of circular particles more proximate to the pipe wall with the increase in the Reynolds number. This finding provides a novel idea and method for further exploring the aggregation rules of non-spherical particles and offers substantial guidance for separating and monitoring pipeline particulate matter via microfluidic technology and other related industrial applications.}, } @article {pmid36871543, year = {2023}, author = {Ram, D and Bhandari, DS and Sharma, K and Tripathi, D}, title = {Progression of blood-borne viruses through bloodstream: A comparative mathematical study.}, journal = {Computer methods and programs in biomedicine}, volume = {232}, number = {}, pages = {107425}, doi = {10.1016/j.cmpb.2023.107425}, pmid = {36871543}, issn = {1872-7565}, mesh = {Humans ; *Hepatitis B ; Blood Viscosity ; Viscosity ; Computer Simulation ; *Viruses ; *HIV Infections ; }, abstract = {BACKGROUND AND OBJECTIVES: Blood-borne pathogens are contagious microorganisms that can cause life-threatening illnesses, and are found in human blood. It is crucial to examine how these viruses spread through blood flow in the blood vessel. Keeping that in view, this study aims to determine how blood viscosity, and diameter of the viruses can affect the virus transmission through the blood flow in the blood vessel. A comparative study of bloodborne viruses (BBVs) such as HIV, Hepatitis B, and C, has been addressed in the present model. A couple stress fluid model is used to represent blood as a carrying medium for virus transmission. The Basset-Boussinesq-Oseen equation is taken into account for the simulation of virus transmission.

METHODS: An analytical approach to derive the exact solutions under the assumption of long wavelength and low Reynolds number approximations is employed. For the computation of the results, a segment (wavelength) of blood vessels about 120 mm with wave velocities in the range of 49 - 190 mm/sec are considered, where the diameter of BBVs ranges from 40-120 nm. The viscosity of the blood varies from 3.5-5.5 × 10[-3]Ns/m[2] which affect the virion motion having a density range 1.03 - 1. 25 g/m[3].

RESULTS: It shows that the Hepatitis B virus is more harmful than other blood-borne viruses considered in the analysis. Patients with high blood pressure are highly susceptible for transmission of BBVs.

CONCLUSIONS: The present fluid dynamics approach for virus spread through blood flow can be helpful in understanding the dynamics of virus propagation inside the human circulatory system.}, } @article {pmid36869078, year = {2023}, author = {Ashin, K and Girishkumar, MS and D'Asaro, E and Jofia, J and Sherin, VR and Sureshkumar, N and Rao, EPR}, title = {Observational evidence of salt finger in the diurnal thermocline.}, journal = {Scientific reports}, volume = {13}, number = {1}, pages = {3627}, pmid = {36869078}, issn = {2045-2322}, abstract = {Due to strong turbulent mixing, the ocean surface boundary layer region is generally not conducive to double diffusion. However, vertical microstructure profiles observations in the northeastern Arabian Sea during May 2019 imply the formation of salt fingers in the diurnal thermocline (DT) region during the daytime. In the DT layer, conditions are favorable for salt fingering: Turner angle values are between 50 and 55° with both temperature and salinity decreasing with depth; shear-driven mixing is weak with a turbulent Reynolds number of about 30. The presence of salt fingering in the DT is confirmed by the presence of staircase-like structures with step sizes larger than the Ozmidov length and by the dissipation ratio that is larger than the mixing coefficient. The unusual daytime salinity maximum in the mixed layer that supports salt fingering is primarily due to a daytime reduction in vertical entrainment of fresh water along with minor contributions from evaporation and horizontal advection and a significant contribution from detrainment processes.}, } @article {pmid36858981, year = {2023}, author = {Arif, I and Leung, RCK and Naseer, MR}, title = {A computational study of trailing edge noise suppression with embedded structural compliance.}, journal = {JASA express letters}, volume = {3}, number = {2}, pages = {023602}, doi = {10.1121/10.0017321}, pmid = {36858981}, issn = {2691-1191}, abstract = {A unique concept for suppression of trailing edge noise scattering from a splitter plate in a low Reynolds number flow is proposed. The key idea of the concept is the adoption of a structural compliance system embedded with a finite number of elastic panels. Specific compliance system designs are devised for promotion of panel structural resonance that effectively absorbs broadband flow/acoustic fluctuation energy responsible for noise scattering. The concept is examined using high-fidelity direct aeroacoustic simulation together with spatiotemporal aeroacoustic-structural interaction analysis. The concept is confirmed feasible and outperforms many similar trailing edge noise reduction approaches reported in the literature.}, } @article {pmid36853773, year = {2023}, author = {Stricker, M and Littfinski, T and Pecher, KH and Lübken, M and Wichern, M}, title = {Hydraulic modeling of a compact stormwater treatment device applying concepts of dynamic similitude.}, journal = {Water science and technology : a journal of the International Association on Water Pollution Research}, volume = {87}, number = {4}, pages = {954-968}, doi = {10.2166/wst.2023.025}, pmid = {36853773}, issn = {0273-1223}, mesh = {*Rain ; *Water Purification ; Water Supply ; Filtration ; Particle Size ; }, abstract = {The development of compact treatment devices (CTDs) with high removal efficiencies and low space requirements is a key objective of urban stormwater treatment. Thus, many devices utilize a combination of sedimentation and upward-flow filtration in a single system. Here, sedimentation is used before filtration, which makes it difficult to evaluate the individual treatment stages separately. This study determines the removal efficiency by sedimentation and the expected filter load in a specific compact treatment device designed for a catchment area of up to 10,000 m[2]. In contrast to a full-scale investigation, small-scale physical hydraulic modeling is applied as a new cost-saving alternative. To validate upscaling laws, tracer signals and particle-size-specific removal efficiencies are determined for two geometrically similar models at different length scales. Thereby, Reynolds number similarity produces similar flow patterns, while the similarity of Hazen numbers allows to upscale removal efficiencies. Upscaling to the full-scale reveals that the filter in the device is only partly loaded by particulate matter that consists mostly of particles ≤63 μm. Thus, sedimentation upstream of a filter is of relevant importance in CTDs. The proposed dimensionless relationship may be used for particles from different catchments and helps to size the device accordingly.}, } @article {pmid36842977, year = {2023}, author = {Lyubimova, TP and Fomicheva, AA and Ivantsov, AO}, title = {Dynamics of a bubble in oscillating viscous liquid.}, journal = {Philosophical transactions. Series A, Mathematical, physical, and engineering sciences}, volume = {381}, number = {2245}, pages = {20220085}, doi = {10.1098/rsta.2022.0085}, pmid = {36842977}, issn = {1471-2962}, abstract = {This article is devoted to the investigation of gaseous bubble dynamics in oscillating viscous liquids of different density values. The study is conducted numerically using the level-set method with a non-stationary approach. The bubble is initially located near the upper wall of the container. The effects of the inclusion and host liquid viscosities on interaction of the bubble with the wall are analysed. The calculations show that in the absence of gravity, for low-viscosity fluids the bubble is attracted to the nearest wall, which is consistent with previous analytical and experimental results. With increasing viscosity, the vibrational attraction to the wall becomes weaker and is then replaced by repulsion, which can be explained by the decelerative effect of viscosity in the boundary layer near the rigid surface, where the average flow becomes less intensive. The dependencies of the repulsion force on the parameter values are obtained by using the balance method (investigation of the gravity level needed to attain the quasi-equilibrium state at a certain distance between the bubble and the wall). The calculations show that the repulsion force grows with decreasing Reynolds number (increase of the viscosity). This article is part of the theme issue 'New trends in pattern formation and nonlinear dynamics of extended systems'.}, } @article {pmid36842115, year = {2023}, author = {Abe, K and Takabe, K and Nakamura, S}, title = {Force Measurement of Bacterial Swimming Using Optical Tweezers.}, journal = {Methods in molecular biology (Clifton, N.J.)}, volume = {2646}, number = {}, pages = {169-179}, pmid = {36842115}, issn = {1940-6029}, mesh = {*Swimming ; *Optical Tweezers ; Biomechanical Phenomena ; Mechanical Phenomena ; Bacteria ; }, abstract = {Velocity is a physical parameter most commonly used to quantify bacterial swimming. In the steady-state motion at a low Reynolds number, the swimming force can be estimated from the swimming velocity and the drag coefficient based on the assumption that the swimming force balances with the drag force exerted on the bacterium. Though the velocity-force relation provides a significant clue to understand the swimming mechanism, the odd configuration of bacteria could develop problems with the accuracy of the force estimation. This chapter describes the force measurement using optical tweezers. The method uses parameters obtained from the shape and movement of a microsphere attached to the bacteria, improving the quantitativeness of force measurement.}, } @article {pmid36828913, year = {2023}, author = {Omrani, V and Targhi, MZ and Rahbarizadeh, F and Nosrati, R}, title = {High-throughput isolation of cancer cells in spiral microchannel by changing the direction, magnitude and location of the maximum velocity.}, journal = {Scientific reports}, volume = {13}, number = {1}, pages = {3213}, pmid = {36828913}, issn = {2045-2322}, mesh = {Humans ; Cell Line, Tumor ; Cell Separation/methods ; *Microfluidic Analytical Techniques ; *Neoplastic Cells, Circulating/pathology ; Microfluidics ; }, abstract = {Circulating tumor cells (CTCs) are scarce cancer cells that rarely spread from primary or metastatic tumors inside the patient's bloodstream. Determining the genetic characteristics of these paranormal cells provides significant data to guide cancer staging and treatment. Cell focusing using microfluidic chips has been implemented as an effective method for enriching CTCs. The distinct equilibrium positions of particles with different diameters across the microchannel width in the simulation showed that it was possible to isolate and concentrate breast cancer cells (BCCs) from WBCs at a moderate Reynolds number. Therefore we demonstrate high throughput isolation of BCCs using a passive, size-based, label-free microfluidic method based on hydrodynamic forces by an unconventional (combination of long loops and U-turn) spiral microfluidic device for isolating both CTCs and WBCs with high efficiency and purity (more than 90%) at a flow rate about 1.7 mL/min, which has a high throughput compared to similar ones. At this golden flow rate, up to 92% of CTCs were separated from the cell suspension. Its rapid processing time, simplicity, and potential ability to collect CTCs from large volumes of patient blood allow the practical use of this method in many applications.}, } @article {pmid36827557, year = {2023}, author = {Moore, CP and Husson, J and Boudaoud, A and Amselem, G and Baroud, CN}, title = {Clogging of a Rectangular Slit by a Spherical Soft Particle.}, journal = {Physical review letters}, volume = {130}, number = {6}, pages = {064001}, doi = {10.1103/PhysRevLett.130.064001}, pmid = {36827557}, issn = {1079-7114}, abstract = {The capture of a soft spherical particle in a rectangular slit leads to a nonmonotonic pressure-flow rate relation at low Reynolds number. Simulations reveal that the flow induced deformations of the trapped particle focus the streamlines and pressure drop to a small region. This increases the resistance to flow by several orders of magnitude as the driving pressure is increased. As a result, two regimes are observed in experiments and simulations: a flow-dominated regime for small particle deformations, where flow rate increases with pressure, and an elastic-dominated regime in which solid deformations block the flow.}, } @article {pmid36820228, year = {2023}, author = {Baba, YD and Chiacchia, M and Patwardhan, SV}, title = {A Novel Method for Understanding the Mixing Mechanisms to Enable Sustainable Manufacturing of Bioinspired Silica.}, journal = {ACS engineering Au}, volume = {3}, number = {1}, pages = {17-27}, pmid = {36820228}, issn = {2694-2488}, abstract = {Bioinspired silica (BIS) has received unmatched attention in recent times owing to its green synthesis, which offers a scalable, sustainable, and economical method to produce high-value silica for a wide range of applications, including catalysis, environmental remediation, biomedical, and energy storage. To scale-up BIS synthesis, it is critically important to understand how mixing affects the reaction at different scales. In particular, successful scale-up can be achieved if mixing time is measured, modeled, and kept constant across different production scales. To this end, a new image analysis technique was developed using pH, as one of the key parameters, to monitor the reaction and the mixing. Specifically, the technique involved image analysis of color (pH) change using a custom-written algorithm to produce a detailed pH map. The degree of mixing and mixing time were determined from this analysis for different impeller speeds and feed injection locations. Cross validation of the mean pH of selected frames with measurements using a pH calibration demonstrated the reliability of the image processing technique. The results suggest that the bioinspired silica formation is controlled by meso- and, to a lesser extent, micromixing. Based on the new data from this investigation, a mixing time correlation is developed as a function of Reynolds number-the first of a kind for green nanomaterials. Further, we correlated the effects of mixing conditions on the reaction and the product. These results provide valuable insights into the scale-up to enable sustainable manufacturing of BIS and other nanomaterials.}, } @article {pmid36813941, year = {2023}, author = {Han, F and Zhao, Y and Liu, M and Hu, F and Peng, Y and Ma, L}, title = {Wetting behavior during impacting bituminous coal surface for dust suppression droplets of fatty alcohol polyoxyethylene ether.}, journal = {Environmental science and pollution research international}, volume = {30}, number = {18}, pages = {51816-51829}, pmid = {36813941}, issn = {1614-7499}, support = {LJ2020JCL008//Scientific research project of Education Department of Liaoning Province/ ; JSK202104//Research Grant of Key Laboratory of Mine Thermodynamic Disasters and Control, Ministry of Education, Liaoning Technical University/ ; 51604143//National Natural Science Foundation of China/ ; }, mesh = {*Coal ; *Dust ; Fatty Alcohols ; Polyethylene Glycols ; Water ; Ethers ; }, abstract = {The wetting behavior of droplets during impacting coal surface widely exists in the dust control process. Understanding the effect of surfactants on the diffusion of water droplets on coal surface is critical. To study the effect of fatty alcohol polyoxyethylene ether (AEO) on the dynamic wetting behavior of droplets on bituminous coal surface, a high-speed camera is used to record the impact process of ultrapure water droplets and three different molecular weight AEO solution droplets. A dynamic evaluation index, dimensionless spreading coefficient ([Formula: see text]), is used to evaluate the dynamic wetting process. The research results show that maximum dimensionless spreading coefficient ([Formula: see text]) of AEO-3, AEO-6, and AEO-9 droplets is greater than that of ultrapure water droplets. With the increase of impact velocity, the [Formula: see text] increases, but the required time decreases. Moderately increasing the impact velocity is conducive to promoting the spreading of droplets on the coal surface. Below the critical micelle concentration (CMC), the concentration of AEO droplets is positively correlated with the [Formula: see text] and the required time. When the polymerization degree increases, the Reynolds number ([Formula: see text]) and Weber number ([Formula: see text]) of droplets decrease, and the [Formula: see text] decreases. AEO can effectively enhance the spreading of droplets on the coal surface, but the increase in polymerization degree can inhibit this process. Viscous force hinders droplet spreading during droplet interaction with the coal surface, and surface tension promotes droplet retraction. Under the experimental conditions of this paper ([Formula: see text], [Formula: see text]), there is a power exponential relationship between [Formula: see text] and [Formula: see text].}, } @article {pmid36813725, year = {2023}, author = {Rahimi, A and Shahsavari, A and Pakzad, H and Moosavi, A and Nouri-Borujerdi, A}, title = {Laminar drag reduction ability of liquid-infused microchannels by considering different infused lubricants.}, journal = {The Journal of chemical physics}, volume = {158}, number = {7}, pages = {074702}, doi = {10.1063/5.0137100}, pmid = {36813725}, issn = {1089-7690}, abstract = {We numerically investigate the pressure drop reduction (PDR) performance of microchannels equipped with liquid-infused surfaces, along with determining the shape of the interface between the working fluid and lubricant within the microgrooves. The effects of different parameters, such as the Reynolds number of working fluid, density and viscosity ratios between the lubricant and working fluid, the ratio of the thickness of the lubricant layer over the ridges to the depth of the groove, and the Ohnesorge number as a representative of the interfacial tension, on the PDR and interfacial meniscus within the microgrooves are comprehensively studied. The results reveal that the density ratio and Ohnesorge number do not significantly affect the PDR. On the other hand, the viscosity ratio considerably affects the PDR, and a maximum PDR of 62% compared to a smooth non-lubricated microchannel is achieved for a viscosity ratio of 0.01. Interestingly, the higher the Reynolds number of the working fluid, the higher the PDR. The meniscus shape within the microgrooves is strongly affected by the Reynolds number of the working fluid. Despite the insignificant effect of interfacial tension on the PDR, the interface shape within the microgrooves is appreciably influenced by this parameter.}, } @article {pmid36810678, year = {2023}, author = {O'Callaghan, F and Lehmann, FO}, title = {Flow development and leading edge vorticity in bristled insect wings.}, journal = {Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology}, volume = {209}, number = {2}, pages = {219-229}, pmid = {36810678}, issn = {1432-1351}, mesh = {Animals ; *Models, Biological ; *Wings, Animal/physiology ; Flight, Animal/physiology ; Insecta/physiology ; Biomechanical Phenomena/physiology ; }, abstract = {Small flying insects such as the tiny thrip Gynaikothrips ficorum have wings with bristles attached to a solid shaft instead of solid membranes. Air passing through the bristle fringe, however, makes bristled insect wings less effective for aerodynamic force production. In this study, we quantified the ability of bristled wings to generate a leading edge vortex (LEV) for lift support during wing flapping, scored its circulation during wing translation, and investigated its behaviour at the stroke reversals. The data were measured in robotic model wings flapping with a generic kinematic pattern at Reynolds number of ~ 3.4, while applying two-dimensional particle image velocimetry. We found that aerodynamic performance due to LEV circulation linearly decreases with increasing bristle spacing. The wings of Gynaikothrips ficorum might thus produce approximately 9% less aerodynamic force for flight than a solid membranous wing. At the stroke reversals, leading and trailing edge vortices dissipate quickly within no more than ~ 2% of the stroke cycle duration. This elevated dissipation makes vortex shedding obsolete during the reversals and allows a quick build-up of counter-vorticity when the wing reverses flapping direction. In sum, our findings highlight the flow conditions associated with bristled wing design in insects and are thus significant for assessing biological fitness and dispersal of insects flying in a viscosity-dominated fluid regime.}, } @article {pmid36789875, year = {2023}, author = {Hamlet, CL and Strickland, WC and Battista, N and Miller, LA}, title = {Multiscale flow between the branches and polyps of gorgonians.}, journal = {The Journal of experimental biology}, volume = {226}, number = {5}, pages = {}, pmid = {36789875}, issn = {1477-9145}, mesh = {Animals ; *Anthozoa ; Hydrodynamics ; }, abstract = {Gorgonians, including sea fans, are soft corals well known for their elaborate branching structure and how they sway in the ocean. This branching structure can modify environmental flows to be beneficial for feeding in a particular range of velocities and, presumably, for a particular size of prey. As water moves through the elaborate branches, it is slowed, and recirculation zones can form downstream of the colony. At the smaller scale, individual polyps that emerge from the branches expand their tentacles, further slowing the flow. At the smallest scale, the tentacles are covered in tiny pinnules where exchange occurs. In this paper, we quantified the gap to diameter ratios for various gorgonians at the scale of the branches, the polyp tentacles and the pinnules. We then used computational fluid dynamics to determine the flow patterns at all three levels of branching. We quantified the leakiness between the branches, tentacles and pinnules over the biologically relevant range of Reynolds numbers and gap-to-diameter ratios, and found that the branches and tentacles can act as either leaky rakes or solid plates depending upon these dimensionless parameters. The pinnules, in contrast, mostly impede the flow. Using an agent-based modeling framework, we quantified plankton capture as a function of the gap-to-diameter ratio of the branches and the Reynolds number. We found that the capture rate depends critically on both morphology and Reynolds number. The results of the study have implications for how gorgonians modify ambient flows for efficient feeding and exchange.}, } @article {pmid36785427, year = {2023}, author = {Liu, W and Yu, Z and Duan, F and Hu, H and Fu, X and Bao, R}, title = {Robust five-degree-of-freedom measurement system with self-compensation and air turbulence protection.}, journal = {Optics express}, volume = {31}, number = {3}, pages = {4652-4666}, doi = {10.1364/OE.480772}, pmid = {36785427}, issn = {1094-4087}, abstract = {A robust five-degree-of-freedom (5-DOF) measurement system is proposed in this paper. The compact optical configuration with high resolution is designed based on lens combination and multiple reflections. Beam drift and dual-beam parallelism are monitored and compensated by autocollimator units and a polarizer unit respectively. In addition, a protection method is proposed to reduce the intensity of air turbulence by reducing the Reynolds number of the beam path. The performance of the system is verified by experiments. The experimental results show that the self-compensation methods and air turbulence protection can effectively improve the accuracy and stability of the system under the long-term interference of external environments. The proposed system has high precision, desirable robustness, and convenient pre-calibration, which can be used for error measurement of precision machines.}, } @article {pmid36779398, year = {2023}, author = {Millett, PC}, title = {Rheology and structure of elastic capsule suspensions within rectangular channels.}, journal = {Soft matter}, volume = {19}, number = {9}, pages = {1759-1771}, doi = {10.1039/d3sm00055a}, pmid = {36779398}, issn = {1744-6848}, abstract = {Three-dimensional simulations of the pressure-driven flow dynamics of elastic capsule suspensions within both slit and rectangular cross-section channels are presented. The simulations utilize the Immersed Boundary Method and the Lattice-Boltzmann Method models. The capsule volume fraction is fixed at 0.1 (i.e., a semi-dilute suspension), while the channel Reynolds number (Re), the capillary number (Ca), and the cross-sectional channel dimensions are systematically varied. Comparing results for slit and rectangular channels, it is found that multi-directional confinement hinders inertial focusing due to the capsule-free layers that develop in the two transverse directions. Furthermore, the thicknesses of the capsule-free layers in the two transverse directions differ when the height and width of the channel are not equal. Both the size and aspect ratio of the channel impact the apparent viscosity. It is found that square channels exhibit maximal viscosity and that holding one dimension fixed while increasing or decreasing the other results in a decrease in viscosity. The results therefore represent an expansion of the Fahraeus-Lindqvist effect from 1D cylindrical channels to 2D rectangular channels.}, } @article {pmid36736259, year = {2023}, author = {Yang, G and Yu, Z and Baki, ABM and Yao, W and Ross, M and Chi, W and Zhang, W}, title = {Settling behaviors of microplastic disks in water.}, journal = {Marine pollution bulletin}, volume = {188}, number = {}, pages = {114657}, doi = {10.1016/j.marpolbul.2023.114657}, pmid = {36736259}, issn = {1879-3363}, mesh = {*Microplastics ; Water ; Plastics ; *Water Pollutants, Chemical/analysis ; }, abstract = {Microplastic (MP) disks have not been studied for settling behaviors in aquatic environments, which affects the transport and fate of MPs. Therefore, settling experiments were conducted on MP disks of three shapes and four common-seen materials. Lighter MP disks (with density ρs = 1.038 g/cm[3] and length l ≤ 5 mm) followed rectilinear vertical trajectories, while heavier MP disks (ρs = 1.161-1.343 g/cm[3] and l = 5 mm) followed zigzag trajectories with oscillations and rotations. The mean terminal settling velocities of MP disks were 19.6-48.8 mm/s. Instantaneous settling velocities of heavier MP disks fluctuated. Existing formulas could not accurately predict the settling velocity of MP disks; thus, a new model was proposed with an error of 15.5 %. Finally, the Red - I* diagram (Red is the disk Reynolds number and I* is the dimensionless moment of inertia) was extended for MP disks to predict settling trajectories.}, } @article {pmid36733611, year = {2022}, author = {Fahim, T and Laouedj, S and Abderrahmane, A and Driss, Z and Tag-ElDin, ESM and Guedri, K and Younis, O}, title = {Numerical study of perforated obstacles effects on the performance of solar parabolic trough collector.}, journal = {Frontiers in chemistry}, volume = {10}, number = {}, pages = {1089080}, pmid = {36733611}, issn = {2296-2646}, abstract = {The current work presents and discusses a numerical analysis of improving heat transmission in the receiver of a parabolic trough solar collector by introducing perforated barriers. While the proposed approach to enhance the collector's performance is promising, the use of obstacles results in increased pressure loss. The Computational Fluid Dynamics (CFD) model analysis is conducted based on the renormalization-group (RNG) k-ɛ turbulent model associated with standard wall function using thermal oil D12 as working fluid The thermo-hydraulic analysis of the receiver tube with perforated obstacles is taken for various configurations and Reynolds number ranging from 18,860 to 81,728. The results are compared with that of the receiver without perforated obstacles. The receiver tube with three holes (PO3) showed better heat transfer characteristics. In addition, the Nusselt number (Nu) increases about 115% with the increase of friction factor 5-6.5 times and the performance evaluation criteria (PEC) changes from 1.22 to 1.24. The temperature of thermal oil fluid attains its maximum value at the exit, and higher temperatures (462.1 K) are found in the absorber tube with perforated obstacles with three holes (PO3). Accordingly, using perforated obstacles receiver for parabolic trough concentrator is highly recommended where significant enhancement of system's performance is achieved.}, } @article {pmid36725545, year = {2023}, author = {Chen, X and Sun, S and Tian, X and Liu, L and Yang, J}, title = {A quasi-two-dimensional fluid experimental apparatus based on tank-in-tank configuration.}, journal = {The Review of scientific instruments}, volume = {94}, number = {1}, pages = {015115}, doi = {10.1063/5.0125679}, pmid = {36725545}, issn = {1089-7623}, abstract = {The fluid tank is an essential facility for experimental research on fluid mechanics. However, owing to the hydrostatic fluid pressure, a fine uniformity of the narrow channel is difficult to be maintained in a tall narrow-channel tank. To address this issue, we proposed a quasi-two-dimensional fluid experimental apparatus based on a "tank-in-tank" configuration and built with an outer tank and an inner tank. The outer tank was cuboid-shaped and used to load the fluid medium, while the inner tank, consisting of two parallel glass plates, was embedded into the outer tank and served as the experimental channel. The hydrostatic pressure acting on the channel was balanced so that a high level of uniformity was maintained over the whole channel. The available height and width of the channel were 2800 and 1500 mm, respectively, while its gap distance could be adaptive from 0 to 120 mm. Experimental research on motion characteristics of circular disks falling in the quasi-2D channel was implemented to investigate the effects of the falling environment and disk geometry. Four distinct falling types were observed, and the wake flow fields of the falling disks were visualized. The Reynolds numbers of falling disks ranged from 400 to 63 000 presently. Chaotic motion and regular motion were demarcated at Re ≈ 30 000. An analytical model was established to predict the final average falling velocity and Reynolds number. Finally, potential directions for future research and improvements to the apparatus were suggested.}, } @article {pmid36714791, year = {2023}, author = {Misiulia, D and Lidén, G and Antonyuk, S}, title = {Secondary Lip Flow in a Cyclone Separator.}, journal = {Flow, turbulence and combustion}, volume = {110}, number = {3}, pages = {581-600}, pmid = {36714791}, issn = {1573-1987}, abstract = {Three secondary flows, namely the inward radial flow along the cyclone lid, the downward axial flow along the external surface of the vortex finder, and the radial inward flow below the vortex finder (lip flow) have been studied at a wide range of flow rate 0.22-7.54 LPM using the LES simulations. To evaluate these flows the corresponding methods were originally proposed. The highly significant effect of the Reynolds number on these secondary flows has been described by equations. The main finding is that the magnitude of all secondary flows decrease with increasing Reynolds number. The secondary inward radial flow along the cyclone lid is not constant and reaches its maximum value at the central radial position between the vortex finder external wall and the cyclone wall. The secondary downward axial flow along the external surface of the vortex finder significantly increases at the lowest part of the vortex finder and it is much larger than the secondary flow along the cyclone lid. The lip flow is much larger than the secondary inward radial flow along the cyclone lid, which was assumed in cyclone models to be equal to the lip flow, and the ratio of these two secondary flows is practically independent of the Reynolds number.}, } @article {pmid36711805, year = {2023}, author = {Chang, R and Davydov, A and Jaroenlak, P and Budaitis, B and Ekiert, DC and Bhabha, G and Prakash, M}, title = {Energetics of the Microsporidian Polar Tube Invasion Machinery.}, journal = {bioRxiv : the preprint server for biology}, volume = {}, number = {}, pages = {}, pmid = {36711805}, support = {R01 AI147131/AI/NIAID NIH HHS/United States ; }, abstract = {UNLABELLED: Microsporidia are eukaryotic, obligate intracellular parasites that infect a wide range of hosts, leading to health and economic burdens worldwide. Microsporidia use an un-usual invasion organelle called the polar tube (PT), which is ejected from a dormant spore at ultra-fast speeds, to infect host cells. The mechanics of PT ejection are impressive. Anncaliia algerae microsporidia spores (3-4 μ m in size) shoot out a 100-nm-wide PT at a speed of 300 μ m/sec, creating a shear rate of 3000 sec [- 1] . The infectious cargo, which contains two nuclei, is shot through this narrow tube for a distance of ~60-140 μ m [1] and into the host cell. Considering the large hydraulic resistance in an extremely thin tube and the low-Reynolds-number nature of the process, it is not known how microsporidia can achieve this ultrafast event. In this study, we use Serial Block-Face Scanning Electron Microscopy to capture 3-dimensional snapshots of A. algerae spores in different states of the PT ejection process. Grounded in these data, we propose a theoretical framework starting with a systematic exploration of possible topological connectivity amongst organelles, and assess the energy requirements of the resulting models. We perform PT firing experiments in media of varying viscosity, and use the results to rank our proposed hypotheses based on their predicted energy requirement, pressure and power. We also present a possible mechanism for cargo translocation, and quantitatively compare our predictions to experimental observations. Our study provides a comprehensive biophysical analysis of the energy dissipation of microsporidian infection process and demonstrates the extreme limits of cellular hydraulics.

STATEMENT OF SIGNIFICANCE: Microsporidia are a group of spore-forming, intracellular parasites that infect a wide range of hosts (including humans). Once triggered, microsporidian spores (3-4 μ m in size) shoot out a specialized organelle called the polar tube (PT) (60-140 μ m long, 100 nm wide) at ultrafast speed (300 μ m/sec), penetrating host cells and acting as a conduit for the transport of infectious cargo. Although this process has fascinated biologists for a century, the biophysical mechanisms underlying PT extrusion are not understood. We thus take a data-driven approach to generate models for the physical basis of PT firing and cargo transport through the PT. Our approach here demonstrates the extreme limits of cellular hydraulics and the potential applications of biophysical approaches to other cellular architectures.}, } @article {pmid36709783, year = {2023}, author = {Jeganathan, V and Alba, K and Ostilla-Mónico, R}, title = {Exploring the origin of turbulent Taylor rolls.}, journal = {Philosophical transactions. Series A, Mathematical, physical, and engineering sciences}, volume = {381}, number = {2243}, pages = {20220130}, doi = {10.1098/rsta.2022.0130}, pmid = {36709783}, issn = {1471-2962}, abstract = {Since Taylor's seminal paper, the existence of large-scale quasi-axisymmetric structures has been a matter of interest when studying Taylor-Couette flow. In this article, we probe their formation in the highly turbulent regime by conducting a series of numerical simulations at a fixed Reynolds number [Formula: see text] while varying the Coriolis parameter to analyse the flow characteristics as the structures arise and dissipate. We show how the Coriolis force induces a one-way coupling between the radial and azimuthal velocity fields inside the boundary layer, but in the bulk, there is a two-way coupling that causes competing effects. We discuss how this complicates the analogy of narrow-gap Taylor-Couette to other convective flows. We then compare these statistics with a similar shear flow without no-slip boundary layers, showing how this double coupling causes very different effects. We finish by reflecting on the possible origins of turbulent Taylor rolls. This article is part of the theme issue 'Taylor-Couette and related flows on the centennial of Taylor's seminal Philosophical Transactions paper (part 1)'.}, } @article {pmid36709780, year = {2023}, author = {Baroudi, L and Majji, MV and Peluso, S and Morris, JF}, title = {Taylor-Couette flow of hard-sphere suspensions: overview of current understanding.}, journal = {Philosophical transactions. Series A, Mathematical, physical, and engineering sciences}, volume = {381}, number = {2243}, pages = {20220125}, doi = {10.1098/rsta.2022.0125}, pmid = {36709780}, issn = {1471-2962}, abstract = {Although inertial particle-laden flows occur in a wide range of industrial and natural processes, there is both a lack of fundamental understanding of these flows and continuum-level governing equations needed to predict transport and particle distribution. Towards this effort, the Taylor-Couette flow (TCF) system has been used recently to study the flow behaviour of particle-laden fluids under inertia. This article provides an overview of experimental, theoretical and computational work related to the TCF of neutrally buoyant non-Brownian suspensions, with an emphasis on the effect of finite-sized particles on the series of flow transitions and flow structures. Particles, depending on their size and concentration, cause several significant deviations from Newtonian fluid behaviour, including shifting the Reynolds number corresponding to transitions in flow structure and changing the possible structures present in the flow. Furthermore, particles may also migrate depending on the flow structure, leading to hysteretic effects that further complicate the flow behaviour. The current state of theoretical and computational modelling efforts to describe the experimental observations is discussed, and suggestions for potential future directions to improve the fundamental understanding of inertial particle-laden flows are provided. This article is part of the theme issue 'Taylor-Couette and related flows on the centennial of Taylor's seminal Philosophical Transactions paper (part 1)'.}, } @article {pmid36688050, year = {2022}, author = {Hasan, HA and Sherza, JS and Abed, AM and Togun, H and Ben Khedher, N and Sopian, K and Mahdi, JM and Talebizadehsardari, P}, title = {Thermal and flow performance analysis of a concentrated linear Fresnel solar collector with transverse ribs.}, journal = {Frontiers in chemistry}, volume = {10}, number = {}, pages = {1074581}, pmid = {36688050}, issn = {2296-2646}, abstract = {This article deals with the impact of including transverse ribs within the absorber tube of the concentrated linear Fresnel collector (CLFRC) system with a secondary compound parabolic collector (CPC) on thermal and flow performance coefficients. The enhancement rates of heat transfer due to varying governing parameters were compared and analyzed parametrically at Reynolds numbers in the range 5,000-13,000, employing water as the heat transfer fluid. Simulations were performed to solve the governing equations using the finite volume method (FVM) under various boundary conditions. For all Reynolds numbers, the average Nusselt number in the circular tube in the CLFRC system with ribs was found to be larger than that of the plain absorber tube. Also, the inclusion of transverse ribs inside the absorber tube increases the average Nusselt number by approximately 115% at Re = 5,000 and 175% at Re = 13,000. For all Reynolds numbers, the skin friction coefficient of the circular tube with ribs in the CLFRC system is larger than that of the plain absorber tube. The coefficient of surface friction reduces as the Reynolds number increases. The performance assessment criterion was found to vary between 1.8 and 1.9 as the Reynolds number increases.}, } @article {pmid36673306, year = {2023}, author = {Fuchs, M and Lubos, N and Kabelac, S}, title = {Numerical Calculation of the Irreversible Entropy Production of Additively Manufacturable Off-Set Strip Fin Heat-Transferring Structures.}, journal = {Entropy (Basel, Switzerland)}, volume = {25}, number = {1}, pages = {}, pmid = {36673306}, issn = {1099-4300}, support = {KK5174901SN0//Federal Ministry for Economic Affairs and Energy/ ; KK5174901SN0//German Federation of Industrial Research Associations/ ; }, abstract = {In this manuscript, off-set strip fin structures are presented which are adapted to the possibilities of additive manufacturing. For this purpose, the geometric parameters, including fin height, fin spacing, fin length, and fin longitudinal displacement, are varied, and the Colburn j-factor and the Fanning friction factor are numerically calculated in the Reynolds number range of 80-920. The structures are classified with respect to their entropy production number according to Bejan. This method is compared with the results from partial differential equations for the calculation of the irreversible entropy production rate due to shear stresses and heat conduction. This study reveals that the chosen temperature difference leads to deviation in terms of entropy production due to heat conduction, whereas the dissipation by shear stresses shows only small deviations of less than 2%. It is further shown that the variation in fin height and fin spacing has only a small influence on heat transfer and pressure drop, while a variation in fin length and fin longitudinal displacement shows a larger influence. With respect to the entropy production number, short and long fins, as well as large fin spacing and fin longitudinal displacement, are shown to be beneficial. A detailed examination of a single structure shows that the entropy production rate due to heat conduction is dominated by the entropy production rate in the wall, while the fluid has only a minor influence.}, } @article {pmid36673217, year = {2022}, author = {Rajupillai, K and Alessa, N and Eswaramoorthi, S and Loganathan, K}, title = {Thermal Behavior of the Time-Dependent Radiative Flow of Water-Based CNTs/Au Nanoparticles Past a Riga Plate with Entropy Optimization and Multiple Slip Conditions.}, journal = {Entropy (Basel, Switzerland)}, volume = {25}, number = {1}, pages = {}, pmid = {36673217}, issn = {1099-4300}, support = {Researchers Supporting Project number (PNURSP2023R59)//Princess Nourah Bint Abdulrahman University/ ; }, abstract = {This communication deliberates the time-reliant and Darcy-Forchheimer flow of water-based CNTs/gold nanoparticles past a Riga plate. In addition, nonlinear radiation, heat consumption and multiple slip conditions are considered. Entropy generation is computed through various flow parameters. A suitable transformation with symmetry variables is invoked to remodel the governing mathematical flow models into the ODE equations. The homotopy analysis scheme and MATLAB bvp4c method are imposed to solve the reduced ODE equations analytically and numerically. The impact of sundry flow variables on nanofluid velocity, nanofluid temperature, skin friction coefficient, local Nusselt number, entropy profile and Bejan number are computed and analyzed through graphs and tables. It is found that the nanofluid velocity is reduced by greater porosity and slip factors. The thickness of the thermal boundary layer increases with increasing radiation, temperature ratio, and heat consumption/generation parameters. The surface drag force is reduced when there is a higher Forchheimer number, unsteadiness parameter and porosity parameter. The amount of entropy created is proportional to the radiation parameter, porosity parameter and Reynolds number. The Bejan number profile increases with radiation parameter, heat consumption/generation parameter and the Forchheimer number.}, } @article {pmid36658185, year = {2023}, author = {Méry, F and Sebbane, D}, title = {Aerodynamic characterisation of porous fairings: pressure drop and Laser Doppler Velocimetry measurements.}, journal = {Scientific data}, volume = {10}, number = {1}, pages = {39}, pmid = {36658185}, issn = {2052-4463}, support = {8605383//EC | EU Framework Programme for Research and Innovation H2020 | H2020 Euratom (H2020 Euratom Research and Training Programme 2014-2018)/ ; }, abstract = {Wind tunnel measurements of pressure drop and steady and unsteady velocity field of a flow through fairing samples are described. 10 samples have been tested in pressure drop among which the velocity fields of 3 samples have been characterized by means of laser Doppler velocimetry. The samples are perforated plates, wiremesh plates or complex 3D geometries resulting from additive manufacturing methods. The Reynolds number of the experiments ranges from 55 000 to 117 000.}, } @article {pmid36649407, year = {2023}, author = {Li, Y and Pahlavan, AA and Chen, Y and Liu, S and Li, Y and Stone, HA and Granick, S}, title = {Oil-on-water droplets faceted and stabilized by vortex halos in the subphase.}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {120}, number = {4}, pages = {e2214657120}, pmid = {36649407}, issn = {1091-6490}, mesh = {*Water ; Surface Tension ; Thermodynamics ; *Convection ; }, abstract = {For almost 200 y, the dominant approach to understand oil-on-water droplet shape and stability has been the thermodynamic expectation of minimized energy, yet parallel literature shows the prominence of Marangoni flow, an adaptive gradient of interfacial tension that produces convection rolls in the water. Our experiments, scaling arguments, and linear stability analysis show that the resulting Marangoni-driven high-Reynolds-number flow in shallow water overcomes radial symmetry of droplet shape otherwise enforced by the Laplace pressure. As a consequence, oil-on-water droplets are sheared to become polygons with distinct edges and corners. Moreover, subphase flows beneath individual droplets can inhibit the coalescence of adjacent droplets, leading to rich many-body dynamics that makes them look alive. The phenomenon of a "vortex halo" in the liquid subphase emerges as a hidden variable.}, } @article {pmid36648820, year = {2023}, author = {Jo, BW and Majid, T}, title = {Enhanced Range and Endurance Evaluation of a Camber Morphing Wing Aircraft.}, journal = {Biomimetics (Basel, Switzerland)}, volume = {8}, number = {1}, pages = {}, pmid = {36648820}, issn = {2313-7673}, support = {2021K2A9A2A06049018//National Research Foundation of Korea/ ; 20210901//InnoScience Co. Ltd/ ; }, abstract = {Flight range, endurance, maneuverability, and agility are the key elements that determine an aircraft's performance. Both conventional and morphing wing aircraft have been well studied and estimated in all aspects of performance. When considering the performance of morphing aircraft, most works address aspects of the aerodynamical performance such as L and D as well as flight envelopes for flight dynamics and control perspectives. However, the actual benefits of adopting morphing technologies in practical aspects such as aircraft operation, mission planning, and sustainability have not been addressed so far. Thus, this paper addresses the practical aspect of the benefits when adopting a camber morphing wing aircraft. Identical geometrical and computational conditions were applied to an already-existing aircraft: the RQ-7a Shadow. The wing structure was switched between a fixed wing and a camber morphing wing to generate conventional and morphing wing geometries. The fixed-wing cases had varying flap deflection angles, and the camber morphing wing cases had varying camber rates from 4% to 8%. Once the CL values of the fixed and morphing wing cases were matched up to two significant figures, the CD and CL/CD were analyzed for these matching cases to calculate the flight endurance, range, and improvement. When NACA 6410 is adopted, a 17% improvement in flight range and endurance average was expected. In the case of NACA 8410, an average 60% improvement was expected.}, } @article {pmid36648720, year = {2023}, author = {Jain, PK and Lanjewar, A and Chaurasiya, PK and Tiwari, D and Sharma, VK}, title = {Experimental testing of solar-based air heater roughed with discrete V-down rib and staggered element.}, journal = {Environmental science and pollution research international}, volume = {30}, number = {15}, pages = {43137-43151}, pmid = {36648720}, issn = {1614-7499}, mesh = {*Sunlight ; *Air ; Hot Temperature ; Ribs ; }, abstract = {A rough rectangular channel of solar-based air heater (SBAH) is made and tested. The work consists of an effort to perceive the proportion of heat discharge and frictional behavior of air passing over a roughened rectangular channel. The absorber surface of SBAH is roughed with discrete V-down rib and staggered element roughness having different values of relative rib pitch (P/e) that ranged from 6 to 14. Fixed parameters such as relative gap size (g/e), relative staggered element pitch (P'/P), numeral of gaps (Ng), relative staggered element size (r/g), and relative rib height (e/D) are considered 4, 0.4, 3,1, and 0.0433, respectively, all throughout the study. The flow Reynolds number (Re) changes from 4000 to 14,000; consequently the Nusselt number (Nu) and friction factor (f) reach up to 2.16 and 2.73 times, respectively, with respect to plane surface. The optimum rise in terms of thermal-hydraulic performance (THP) is gained analogous to a P/e of 10. The correlation for heat transfer function, R(e[+]), and roughness function, G(e[+]), is given to anticipate the performance of roughness.}, } @article {pmid36643326, year = {2022}, author = {Voskoboinick, V and Onyshchenko, A and Voskoboinyk, O and Makarenkova, A and Voskobiinyk, A}, title = {Junction flow inside and around three-row cylindrical group on rigid flat surface.}, journal = {Heliyon}, volume = {8}, number = {12}, pages = {e12595}, doi = {10.1016/j.heliyon.2022.e12595}, pmid = {36643326}, issn = {2405-8440}, abstract = {Groups of bluff bodies are widespread in nature and technology. These are the supports of bridge crossings, high-rise buildings in cities, offshore drilling and wind platforms, algae and vegetation in the seas and rivers, forests and other objects. The flow of air or water around such structures has a complex vortex and jet character and requires significant efforts in the process of scientific research to improve the environmental situation and reduce material and technical costs in the process of operating such structures. The purpose of the research is study the features of the generation and evolution of vortex and jet flows near and inside the three-row group of cylinders, which are installed on the rigid flat surface. The results of experimental studies showed that the flow around the group of cylinders had a complex unsteady nature, which is due to the interaction of vortex and jet flows typical flow elements with the three-row cylindrical group, which was located installed on the rigid flat surface. The three-row cylindrical group (31 piles with a diameter of 0.027 m) is a model of a bridge support, which was streamlined at a velocity of 0.06 m/s to 0.5 m/s (Reynolds number Red=(1600-6700) and Froude number Fr=(0.04-0.18)). Visual investigations and measurements of the velocity field were carried out inside and around the three-row structure. The features of the formation and evolution of vortex and jet flows inside and near the cylindrical group were established. Integral, spectral and correlation characteristics of the velocity fluctuation field were obtained. Mean, root-mean-square values of velocity and probability density functions of velocity fluctuations integrally displayed the changes in the velocity field in the spatial and temporal domain in the junction area of grillage and plate. The power spectral densities of velocity fluctuations and mutual correlation functions made it possible to study the features of the generation of the velocity fluctuation field in the frequency domain and its interrelationships in space. It was revealed that the velocity field inside the horseshoe vortex structures was multimodal. The spectral levels of velocity fluctuations at the periphery of the quasistable horseshoe vortex structures were higher than in the cores of these structures. The highest levels of the velocity fluctuation spectra were observed in front of the second lateral cylinder where the interaction of the vortex and jet flows took place. Discrete peaks in the spectral levels of velocity fluctuations are found at the frequencies of formation of large-scale wake vortices and the frequencies of formation of small-scale vortex structures of the shear layer, which are due to the Kelvin-Helmholtz instability. It has been established that the frequency of formation of shear layer vortices is (10-40) times higher than the frequency of formation of wake vortices.}, } @article {pmid36622597, year = {2023}, author = {Munusamy, A and Barik, D and Sharma, P and Medhi, BJ and Bora, BJ}, title = {Performance analysis of parabolic type solar water heater by using copper-dimpled tube with aluminum coating.}, journal = {Environmental science and pollution research international}, volume = {}, number = {}, pages = {}, pmid = {36622597}, issn = {1614-7499}, abstract = {A solar water heater has been developed to convert solar radiation into heat for use in residential and commercial settings. The collector makes up the bulk of a solar water heating system. The solar energy is captured by the collector and transferred to the tube that delivers the working fluid, water. In addition to the collector's tube, which carries the working fluid, researchers have focused on the design of the collector's tube. This paper examines the performance of a parabolic plate solar water heater that uses a copper dimpled tube with aluminum-coated tube channels. During the test, the flow rate of base fluid was in the range of 1.0 to 3.0 kg/min in steps of 0.5. The performance of the solar water heater was also evaluated and verified using CFD. The test data such as friction factor, Reynolds number, uncertainty analysis, Nusselt number, solar collector efficiency, coefficient of convective heat transfer, linear dimpled tube velocity analysis, achieving maximum energy efficiency and thermal efficiency have been used to generate parametric values for parabolic plate solar water heaters. The results suggest that the best outcomes can be achieved with a mass flow rate of 2.5 kg/min and the overall thermal efficiency was raised to 31.85%, which is 11% greater than that of the plain tube with base fluid. At mass flow rates of 2.5 kg/min, the pressure drop was found to be 6.24% higher than that of 3.0 kg/min. The experimental results were analyzed and compared with the CFD results, and the overall deviation was ± 3.24% which is in the acceptable range.}, } @article {pmid36597964, year = {2023}, author = {Kanies, OS and Kremer, KR and Mason, BM and Dudley, MG and Hlavay, JM and Miller, CT and Spero, RC and Fisher, JK}, title = {A modular microfluidic device that uses magnetically actuatable microposts for enhanced magnetic bead-based workflows.}, journal = {Lab on a chip}, volume = {23}, number = {2}, pages = {330-340}, pmid = {36597964}, issn = {1473-0189}, support = {R41 GM136084/GM/NIGMS NIH HHS/United States ; R42 GM136084/GM/NIGMS NIH HHS/United States ; R44 AI150263/AI/NIAID NIH HHS/United States ; }, mesh = {*Microfluidic Analytical Techniques ; Workflow ; Microfluidics/methods ; Immunomagnetic Separation ; Magnetic Phenomena ; }, abstract = {Magnetic beads have been widely and successfully used for target enrichment in life science assays. There exists a large variety of commercially available magnetic beads functionalized for specific target capture, as well as options that enable simple surface modifications for custom applications. While magnetic beads are ideal for use in the macrofluidic context of typical laboratory workflows, their performance drops in microfluidic contexts, such as consumables for point-of-care diagnostics. A primary cause is the diffusion-limited analyte transport in these low Reynolds number environments. A new method, BeadPak, uses magnetically actuatable microposts to enhance analyte transport, improving yield of the desired targets. Critical parameters were defined for the operation of this technology and its performance characterized in canonical life-science assays. BeadPak achieved up to 1000× faster capture than a microfluidic chamber relying on diffusion alone, enabled a significant specimen concentration via volume reduction, and demonstrated compatibility with a range of biological specimens. The results shown in this work can be extended to other systems that utilize magnetic beads for target capture, concentration, and/or purification.}, } @article {pmid36597923, year = {2023}, author = {Tingting, Q and Jianzhong, L and Zhenyu, O and Jue, Z}, title = {Settling mode of a bottom-heavy squirmer in a narrow vessel.}, journal = {Soft matter}, volume = {19}, number = {4}, pages = {652-669}, doi = {10.1039/d2sm01442d}, pmid = {36597923}, issn = {1744-6848}, abstract = {The lattice Boltzmann-immersed boundary (IB-LB) method is used to numerically simulate the sedimentation motion of a single two-dimensional, bottom-heavy squirmer in a narrow vessel. The effects of the swimming Reynolds number Res = 0.1-3, eccentricity distance l = 0.15d-0.75d, and density ratio of squirmer to fluid γ = 1.1-2.0 on the settlement motion characteristics are investigated and analyzed. The results showed that four settling modes exist: vertical motion, unilateral oscillation, oscillation, and tilt. The bottom-heavy neutral squirmer and puller settle in the vessel during vertical motion when Res is 0.1-1.5. By increasing Res and swimming strength |β|, the bottom-heavy squirmer becomes more self-driven, shifting its settling mode from vertical motion to unilateral oscillation or oscillation. Increasing l or |β| does not affect the bottom-heavy neutral squirmer and puller's vertical settling mode but shifts the bottom-heavy pusher's settling mode from unilateral oscillation to oscillation or oscillation to unilateral oscillation. Similarly, altering γ or |β| has no impact on the eccentric neutral squirmer and puller's settling mode; however, pushers will switch from oscillation mode to attraction mode or from oscillation mode to tilt mode. Additionally, it was found that after the squirmer collided with the bottom wall, the bottom-heavy squirmer settled at the bottom of the vessel in a different state of motion.}, } @article {pmid36583152, year = {2022}, author = {Abed, AM and Mouziraji, HR and Bakhshi, J and Dulaimi, A and Mohammed, HI and Ibrahem, RK and Ben Khedher, N and Yaïci, W and Mahdi, JM}, title = {Numerical analysis of the energy-storage performance of a PCM-based triplex-tube containment system equipped with arc-shaped fins.}, journal = {Frontiers in chemistry}, volume = {10}, number = {}, pages = {1057196}, pmid = {36583152}, issn = {2296-2646}, abstract = {This study numerically intends to evaluate the effects of arc-shaped fins on the melting capability of a triplex-tube confinement system filled with phase-change materials (PCMs). In contrast to situations with no fins, where PCM exhibits relatively poor heat response, in this study, the thermal performance is modified using novel arc-shaped fins with various circular angles and orientations compared with traditional rectangular fins. Several inline and staggered layouts are also assessed to maximize the fin's efficacy. The effect of the nearby natural convection is further investigated by adding a fin to the bottom of the heat-storage domain. Additionally, the Reynolds number and temperature of the heat-transfer fluid (HTF) are evaluated. The outcomes showed that the arc-shaped fins could greatly enhance the PCMs' melting rate and the associated heat-storage properties. The melting rate is 17% and 93.1% greater for the case fitted with an inline distribution of the fins with a circular angle of 90° and an upward direction, respectively, than the cases with uniform rectangular fins and no fins, which corresponded to the shorter melting time of 14.5% and 50.4%. For the case with arc-shaped fins with a 90° circular angle, the melting rate increases by 9% using a staggered distribution. Compared to the staggered fin distribution, adding an extra fin to the bottom of the domain indicates adverse effects. The charging time reduces by 5.8% and 9.2% when the Reynolds number (Re) rises from 500 to 1000 and 1500, respectively, while the heat-storage rate increases by 6.3% and 10.3%. When the fluid inlet temperature is 55°C or 50°C, compared with 45°C, the overall charging time increases by 98% and 47%, respectively.}, } @article {pmid36579881, year = {2022}, author = {Issa, M and Haupt, D and Muddemann, T and Kunz, U and Sievers, M}, title = {Investigation of an electrolysis system with boron-doped diamond anode and gas diffusion cathode to remove water micropollutants.}, journal = {Water science and technology : a journal of the International Association on Water Pollution Research}, volume = {86}, number = {12}, pages = {3236-3247}, doi = {10.2166/wst.2022.390}, pmid = {36579881}, issn = {0273-1223}, mesh = {*Diamond ; Boron ; Water ; Wastewater ; Electrolysis/methods ; Oxidation-Reduction ; Electrodes ; *Water Pollutants, Chemical/analysis ; }, abstract = {Using electrolysis systems to degrade organics in wastewater encourages this technique to remove micropollutants (MPs) in different types of water. In this work, a cell consisting of an anode as a boron-doped diamond (BDD) electrode combined with a gas diffusion (GDE) cathode without a separator showed that MPs degradation can be effectively achieved. Investigating different operating parameters, it was stated that applying a low current density (2 mA/cm[2]) and setting the Reynolds number of the electrolyte flow through the cell at the laminar range raised the treatment time by 3-fold at the same energy demand. This arrangement increased the MPs removal. Some substances like diclofenac were removed up to 84% at a longer treatment time of 180 min coupled with an increase in energy demand. The results at the mentioned parameters indicated an adequate generation rate of radicals needed to remove MPs and the oxidation reactions were promoted. The results show high potential to the investigated electrolysis system in removing MPs in wastewater under considering the need for further reduction of the energy demand.}, } @article {pmid36574794, year = {2023}, author = {Al-Amshawee, SKA and Yunus, MYBM}, title = {Electrodialysis desalination: The impact of solution flowrate (or Reynolds number) on fluid dynamics throughout membrane spacers.}, journal = {Environmental research}, volume = {219}, number = {}, pages = {115115}, doi = {10.1016/j.envres.2022.115115}, pmid = {36574794}, issn = {1096-0953}, mesh = {Hydrodynamics ; *Membranes, Artificial ; *Water Purification/instrumentation/methods ; Salinity ; *Dialysis/instrumentation/methods ; Electrochemistry/instrumentation/methods ; }, abstract = {The incorporation of a spacer among membranes has a major influence on fluid dynamics and performance metrics. Spacers create feed channels and operate as turbulence promoters to increase mixing and reduce concentration/temperature polarization effects. However, spacer geometry remains unoptimized, and studies continue to investigate a wide range of commercial and custom-made spacer designs. The in-depth discussion of the present systematic review seeks to discover the influence of Reynolds number or solution flowrate on flow hydrodynamics throughout a spacer-filled channel. A fast-flowing solution sweeping one membrane's surface first, then the neighboring membrane's surface produces good mixing action, which does not happen commonly at laminar solution flowrates. A sufficient flowrate can suppress the polarization layer, which may normally require the utilization of a simple feed channel rather than complex spacer configurations. When a recirculation eddy occurs, it disrupts the continuous flow and effectively curves the linear fluid courses. The higher the flowrate, the better the membrane performance, the higher the critical flux (or recovery rate), and the lower the inherent limitations of spacer design, spacer shadow effect, poor channel hydrodynamics, and high concentration polarization. In fact, critical flow achieves an acceptable balance between improving flow dynamics and reducing the related trade-offs, such as pressure losses and the occurrence of concentration polarization throughout the cell. If the necessary technical flowrate is not used, the real concentration potential for transport is relatively limited at low velocities than would be predicted based on bulk concentrations. Electrodialysis stack therefore may suffer from the dissociation of water molecules. Next studies should consider that applying a higher flowrate results in greater process efficiency, increased mass transfer potential at the membrane interface, and reduced stack thermal and electrical resistance, where pressure drop should always be indicated as a consequence of the spacer and circumstances used, rather than a problem.}, } @article {pmid36562423, year = {2023}, author = {de Timary, G and Rousseau, CJ and Van Melderen, L and Scheid, B}, title = {Shear-enhanced sorting of ovoid and filamentous bacterial cells using pinch flow fractionation.}, journal = {Lab on a chip}, volume = {23}, number = {4}, pages = {659-670}, doi = {10.1039/d2lc00969b}, pmid = {36562423}, issn = {1473-0189}, mesh = {*Escherichia coli ; Rotation ; Cell Movement ; }, abstract = {In this paper, we experimentally investigate the influence of the flow rate on the trajectory of ovoid and filamentous bacterial cells of E. coli in a low aspect ratio pinch flow fractionation device. To that aim, we vary the Reynolds number over two orders of magnitude, while monitoring the dynamics of the cells across our device. At low flow rates, filamentous cells adopt several rotational motions in the pinched segment, which are induced both by the shear rate and by their close interactions with the nearest wall. As a result, the geometrical centre of the filamentous cells deviates towards the centre of the channel, which increases their effective sorting diameter depending on the length of their major axis as well as on the rotational mode they adopt in the pinch. As the flow rate increases, particles are forced to align vertically in the pinch, in the direction of the main shear gradient, which reduces the amplitude of the lateral deviation generated by their rotation. The trajectory of the particles in the expansion is directly determined by their position at the pinch outlet. As a consequence, the position of the filamentous cells at the outlet of the device strongly depends on the flow rate as well as on the length of their major axis. Based on these observations we optimized the flow conditions to successfully extract an ultra high purity sample of filamentous cells from a solution containing mainly ovoid cells.}, } @article {pmid36562333, year = {2023}, author = {Marnoto, S and Hashmi, SM}, title = {Application of droplet migration scaling behavior to microchannel flow measurements.}, journal = {Soft matter}, volume = {19}, number = {3}, pages = {565-573}, doi = {10.1039/d2sm00980c}, pmid = {36562333}, issn = {1744-6848}, abstract = {In confined channels in low Reynolds number flow, droplets drift perpendicular to the flow, moving across streamlines. The phenomenon has proven useful for understanding microfluidic droplet separation, drug delivery vehicle optimization, and single-cell genomic amplification. Particles or droplets undergo several migration mechanisms including wall migration, hydrodynamic diffusion, and migration down gradients of shear. In simple shear flow only wall migration and hydrodynamic diffusion are present. In parabolic flow, droplets also move down gradients of shear. The resulting separation depends on parameters including particle size and stiffness, concentration, and flow rate. Computational methods can incorporate these effects in an exact manner to predict margination phenomena for specific systems, but do not generate a descriptive parametric dependence. In this paper, we present a scaling model that elucidates the parametric dependence of margination on emulsion droplet size, volume fraction, shear rate and suspending fluid viscosity. We experimentally measure the droplet depletion layer of silicone oil droplets and compare the results to theoretical scaling behavior that includes hydrodynamic diffusion and wall migration with and without an added shear-gradient migration. Results demonstrate the viability and limitations of applying a simple scaling behavior to experimental systems to describe parametric dependence. Our conclusions open the possibility for parametric descriptions of migration with broad applicability to particle and droplet systems.}, } @article {pmid36559702, year = {2022}, author = {Ayas, M and Skočilas, J and Štípek, J and Gutiérrez, CA and Žitný, R and Jirout, T}, title = {An Approximate Method for Predicting the Friction Factor of Viscoplastic Shear-Thinning Fluids in Non-Circular Channels of Regular Cross-Sections.}, journal = {Polymers}, volume = {14}, number = {24}, pages = {}, pmid = {36559702}, issn = {2073-4360}, abstract = {The objective of this study is to provide a straightforward generalized simple and quick method for the prediction of the friction factor for fully developed laminar flow of viscoplastic shear-thinning fluids in non-circular channels of regular cross-sections. The most frequently represented substances processed under these conditions are polymers in the processing and plastics industry. A generalized approximate method was proposed to express the relationship between the friction factor and the Reynolds number for the Herschel-Bulkley rheological model. This method uses the generalized Reynolds number for power-law fluids. Moreover, an additional simplified method for rapid engineering calculations was obtained as well. The suggested method was verified by comparing experimental data for concentric annulus found in the literature and results from simulations for concentric annulus, rectangular, square duct with a central cylindrical core and elliptical cross-sections. The results showed that the suggested methods enable us to estimate the friction factor with high accuracy for the investigated geometries.}, } @article {pmid36559442, year = {2022}, author = {Moriconi, L and Pereira, RM}, title = {Statistics of extreme turbulent circulation events from multifractality breaking.}, journal = {Physical review. E}, volume = {106}, number = {5-1}, pages = {054121}, doi = {10.1103/PhysRevE.106.054121}, pmid = {36559442}, issn = {2470-0053}, abstract = {Recent numerical explorations of extremely intense circulation fluctuations at high Reynolds number flows have brought to light novel aspects of turbulent intermittency. Vortex gas modeling ideas, which are related to a picture of turbulence as a dilute system of vortex tube structures, have been introduced alongside such developments, leading to accurate descriptions of the core and the intermediate tails of circulation probability distribution functions (cPDFs), as well as the scaling exponents associated to statistical moments of circulation. We extend the predictive reach of the vortex gas picture of turbulence by emphasizing that multifractality breaking, one of its salient phenomenological ingredients, is the key concept to disclose the asymptotic form of cPDF tails. A remarkable analytical agreement is found with previous results derived within the framework of the instanton approach to circulation intermittency, a functional formalism devised to single out the statistically dominant velocity configurations associated to extreme circulation events.}, } @article {pmid36559415, year = {2022}, author = {Maity, R and Burada, PS}, title = {Near- and far-field hydrodynamic interaction of two chiral squirmers.}, journal = {Physical review. E}, volume = {106}, number = {5-1}, pages = {054613}, doi = {10.1103/PhysRevE.106.054613}, pmid = {36559415}, issn = {2470-0053}, abstract = {Hydrodynamic interaction strongly influences the collective behavior of microswimmers. With this work, we study the behavior of two hydrodynamically interacting self-propelled chiral swimmers in the low Reynolds number regime, considering both the near- and far-field interactions. We use the chiral squirmer model [see Burada et al., Phys. Rev. E 105, 024603 (2022)2470-004510.1103/PhysRevE.105.024603], a spherically shaped body with nonaxisymmetric surface slip velocity, which generalizes the well-known squirmer model. The previous work was restricted only to the case, while the far-field hydrodynamic interaction was influential among the swimmers. It did not approach the scenario while both the swimmers are very close and lubrication effects become dominant. We calculate the lubrication force between the swimmers when they are very close. By varying the slip coefficients and the initial configuration of the swimmers, we investigate their hydrodynamic behavior. In the presence of lubrication force, the swimmers either repel each other or exhibit bounded motion where the distance between the swimmers alters periodically. We identify the possible behaviors exhibited by the chiral squirmers, such as monotonic divergence, divergence, and bounded, as was found in the previous study. However, in the current study, we observe that both the monotonic convergence and the convergence states are converted into divergence states due to the arising lubrication effects. The lubrication force favors the bounded motion in some parameter regimes. This study helps to understand the collective behavior of dense suspension of ciliated microorganisms and artificial swimmers.}, } @article {pmid36559353, year = {2022}, author = {Lutz, T and Richter, SK and Menzel, AM}, title = {Effect of boundaries on displacements and motion in two-dimensional fluid or elastic films and membranes.}, journal = {Physical review. E}, volume = {106}, number = {5-1}, pages = {054609}, doi = {10.1103/PhysRevE.106.054609}, pmid = {36559353}, issn = {2470-0053}, abstract = {Thin fluid or elastic films and membranes are found in nature and technology, for instance, as confinements of living cells or in loudspeakers. When applying a net force, the resulting flows in an unbounded two-dimensional incompressible low-Reynolds-number fluid or displacements in a two-dimensional linearly elastic solid seem to diverge logarithmically with the distance from the force center, which has led to some debate. Recently, we have demonstrated that such divergences cancel when the total (net) force vanishes. Here, we illustrate that if a net force is present, the boundaries play a prominent role. Already a single no-slip boundary regulates the flow and displacement fields and leads to their decay to leading order inversely in distance from a force center and the boundary. In other words, it is the boundary that stabilizes the system in this situation, unlike the three-dimensional case, where an unbounded medium by itself is able to absorb a net force. We quantify the mobility and displaceability of an inclusion as a function of the distance from the boundary, as well as interactions between different inclusions. In the case of free-slip boundary conditions, a kinked boundary is necessary to achieve stabilization.}, } @article {pmid36557435, year = {2022}, author = {Guan, X and Xie, Z and Nan, G and Xi, K and Lu, Z and Ge, Y}, title = {Thermal-Hydrodynamic Behavior and Design of a Microchannel Pin-Fin Hybrid Heat Sink.}, journal = {Micromachines}, volume = {13}, number = {12}, pages = {}, pmid = {36557435}, issn = {2072-666X}, support = {51979278 and 51579244//National Natural Science Foundation of China/ ; }, abstract = {A three-dimensional convective heat transfer model of a microchannel pin-fin hybrid heat sink was established. Considering the non-uniform heat generation of 3D stacked chips, the splitting distance of pin-fins was optimized by minimizing the maximum heat sink temperature under different heat fluxes in the hotspot, the Reynolds numbers at the entrance of the microchannel, and the proportions of the pin-fin volume. The average pressure drop and the performance evaluation criteria were considered to be the performance indexes to analyze the influence of each parameter on the flow performance and comprehensive performance, respectively. The results showed that the maximum temperature of the hybrid heat sink attained a minimum value with an increase in the splitting distance. The average pressure drop in the center passage of the microchannel first increased and then decreased. Furthermore, the optimal value could not be simultaneously obtained with the maximum temperature. Therefore, it should be comprehensively considered in the optimization design. The heat flux in the hotspot was positively correlated with the maximum heat sink temperature. However, it had no effect on the flow pressure drop. When the Reynolds number and the pin-fin diameter increased, the maximum heat sink temperature decreased and the average pressure drop of the microchannel increased. The comprehensive performance of the hybrid heat sink was not good at small Reynolds numbers, but it significantly improved as the Reynolds number gradually increased. Choosing a bigger pin-fin diameter and the corresponding optimal value of the splitting distance in a given Reynolds number would further improve the comprehensive performance of a hybrid heat sink.}, } @article {pmid36547837, year = {2023}, author = {Salman, M and Chauhan, R and Singh, T and Prabakaran, R and Kim, SC}, title = {Experimental investigation and optimization of dimple-roughened impinging jet solar air collector using a novel AHP-MABAC approach.}, journal = {Environmental science and pollution research international}, volume = {30}, number = {13}, pages = {36259-36275}, pmid = {36547837}, issn = {1614-7499}, mesh = {Reproducibility of Results ; *Sunlight ; }, abstract = {The effect of the flow and geometric parameters of a dimple-roughened absorber plate on the enactment of solar air collectors (SACs) with air-impinged jets was investigated in this study. The performance-defining criteria (PDCs) of a jet-impinged dimple-roughened SAC (JIDRSAC)-forced convection airflow system are significantly affected by variations in the system's control factors (CFs), such as the arc angle (αaa) ranging from 30° to 75°, dimple pitch ratio (pd/Dh) ranging from 0.269 to 1.08, and dimple height ratio (ed/Dh) ranging from 0.016 to 0.0324. The constant parameters of the jet slot are a stream-wise pitch ratio (Xi/Dhd) is 1.079, a span-wise pitch ratio (Yi/Dhd) is 1.619, and a jet diameter(Di/Dhd) is 0.081. Based on the combined approach of the analytic hierarchy process and multi-attributive border approximation area comparison (AHP-MABAC), the Reynolds number (Re) = 15,000, αaa = 60°, pd/Dh = 0.27, and ed/Dh = 0.027 depicted the best alternative (A-9) set among 16 alternatives to deliver the optimal performance of the JIDRSAC. The jet impingement pass compared to the smooth pass, the Nusselt number increased by 2.16-2.81, and friction factor increased by 3.35-5.95, and JIDRSAC was compared to the jet impingement pass, exhibiting an enhancement in Nusselt number and friction factor in the range of 0.55-0.80 and 0.05-0.15, respectively. In addition, sensitivity analysis is used to examine the ranking's stability and reliability in relation to the PDC weights.}, } @article {pmid36547831, year = {2022}, author = {Raju, LB and Sastry, GR and Gugulothu, SK and Kumar, R and Balakrishnan, D}, title = {Computational analysis on solar air heater with combination of alternate dimple protrusions and intrusions on absorber plate with one rounded corner triangular duct.}, journal = {Environmental science and pollution research international}, volume = {}, number = {}, pages = {}, pmid = {36547831}, issn = {1614-7499}, abstract = {This study focuses on improving heat transfer by converting one of the corners of the duct to a rounded structure. To study the effect of dimpled shaped protrusions and intrusions on the rounded corner triangular duct with a constant radius of curvature by varying relative streamwise distance (z/e) with a constant transverse distance x'/e = 10,14 and 18. Steady-state, turbulent flow heat transfer under thermal boundary conditions is to be analyzed by varying different Reynolds numbers (5600 to 21000). The duct with dimple-shaped protrusions and intrusions is compared with a simple triangular duct. Optimization of relative horizontal distance (z'/e) by keeping constant protrusion to protrusion distance as z/e = 28 and relative transverse distance as x/e = 10, 14, and 18. It was noted that there was a significant loss in friction and a rise in heat transfer. The relationship between friction factor and Nusselt number was formulated using operating and roughness parameters, using the data collected from the numerical investigation. The friction factor increases significantly with roughness elements, and it is maximum for x'/e = 20 at a low Reynolds number. Nusselt number increases with roughness elements, and it is maximum for x'/e = 14 for all Reynolds numbers and all the models. Enhancement of Nusselt number is due to increase of local heat transfer because of local vortex neat heat transfer zone. The maximum outlet temperature is obtained at a low Reynolds number. The maximum temperature of the heated surface is obtained for Rc = 0.67 h and the minimum for Rc = 0.33 h.}, } @article {pmid36533860, year = {2022}, author = {Lim, S and Du, Y and Lee, Y and Panda, SK and Tong, D and Khalid Jawed, M}, title = {Fabrication, control, and modeling of robots inspired by flagella and cilia.}, journal = {Bioinspiration & biomimetics}, volume = {18}, number = {1}, pages = {}, doi = {10.1088/1748-3190/aca63d}, pmid = {36533860}, issn = {1748-3190}, mesh = {*Cilia ; *Flagella ; Locomotion ; }, abstract = {Flagella and cilia are slender structures that serve important functionalities in the microscopic world through their locomotion induced by fluid and structure interaction. With recent developments in microscopy, fabrication, biology, and modeling capability, robots inspired by the locomotion of these organelles in low Reynolds number flow have been manufactured and tested on the micro-and macro-scale, ranging from medicalin vivomicrobots, microfluidics to macro prototypes. We present a collection of modeling theories, control principles, and fabrication methods for flagellated and ciliary robots.}, } @article {pmid36517549, year = {2022}, author = {Hafez, NM and Alsemiry, RD and Alharbi, SA and Abd-Alla, AM}, title = {Peristaltic transport characteristics of a second-grade dusty fluid flown with heat transfer through a tube revisited.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {21605}, pmid = {36517549}, issn = {2045-2322}, abstract = {This paper provides a rudimentary insight into the influence of heat transfer on the transport characteristics of a second-grade dusty fluid flown in a flexible tube with walls subjected to the peristaltic motion. Both dust particles and fluid movements were modeled using the coupled differential equations. The effects of different types of parameters such as Reynolds number, Prandtl number, Grashof number, wave number, wave amplitude ratio, second grade parameter as well as nature of the heat source and sink are studies on the dust particles velocity, fluid velocity, temperature, pressure profiles of the fluid and streamline patterns of the fluid. The derived equations were solved analytically via the standard perturbation method to determine the fluid temperature, streamline pattern and velocity of the dust particles as well as fluid. The values in the increase of pressure and frictional forces were calculated numerically using DSolve of the Mathematica 11 software (https://www.wolfram.com/mathematica/new-in-11/). In addition, the trapping mechanisms were ascertained by computing the streamlines and various physical parameters. The obtained results were validated with the state-of-the-art literature reports. It was claimed that our systematic approach may constitute a basis for accurately examining the impact of heat transfer on the peristaltic transport of a complex fluid through narrow tubes, useful for diverse medical applications such as the gastric fluid flow through the small intestine during endoscopy. Numerical results are computed and discussed numerically and presented through graphs. The impacts of pertinent parameters on the aforementioned quantities are examined by plotting graphs on the basis of computational results. The results indicate that the effect of parameters is very pronounced. A suitable comparison has been made with the prior results in the literature as a limiting case of the considered problem.}, } @article {pmid36513785, year = {2022}, author = {Abd-Alla, AM and Abo-Dahab, SM and Thabet, EN and Abdelhafez, MA}, title = {Heat and mass transfer for MHD peristaltic flow in a micropolar nanofluid: mathematical model with thermophysical features.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {21540}, pmid = {36513785}, issn = {2045-2322}, abstract = {According to a survey of the literature, nanofluids are superior to traditional fluids at transferring heat. A detailed analysis of the models mentioned above is crucial since there are large gaps in the illumination of current solutions for improving heat transfer in nanomaterials. The ongoing investigation's purpose is to ascertain the tiny size gold particles drift in free with the heat and mass transfer, buoyancy forces, thermophoresis, and Brownian motion of a micropolar nanofluid being transported through a porous medium in an asymmetric channel with a uniform magnetic field using a long-wavelength and low Reynolds number approximation. The resulting dimensionless nonlinear governing equations have been numerically solved using a MATLAB software and the Runge-Kutta-Fehlberg integration scheme. Two comparisons with previously investigated problems are also made to confirm our findings, and an excellent concurrence is discovered. As a result, trustworthy results are being given. Numerical solutions are used to describe the effects of different thermal-fluidic parameters on velocity profiles, temperature, concentration, micropolar rotation, pressure gradient, shear stress, heat flux, and nanoparticle volume flux, etc. Tables, graphs, and bar charts are used to present and discuss numerical results that have been produced. A comparison of the resulting numerical solution to earlier literature also reveals a satisfactory level of agreement. Insight into real-world applications such nanofluidic, energy conservation, friction reduction, and power generation are provided by this work. Furthermore, the Brownian and thermophoresis parameters behave significantly differently in a concentration field. On the other hand, the study puts forward an important note that for peristaltic flow of a micropolar fluid with nanoparticles can be controlled by suitably adjusting the micropolar parameter, thermophoresis parameter, nanoparticle Grashof number, and Brownian motion parameter.}, } @article {pmid36506398, year = {2022}, author = {Shuvo, MS and Hasib, MH and Saha, S}, title = {Entropy generation and characteristics of mixed convection in lid-driven trapezoidal tilted enclosure filled with nanofluid.}, journal = {Heliyon}, volume = {8}, number = {12}, pages = {e12079}, pmid = {36506398}, issn = {2405-8440}, abstract = {The investigation of steady, incompressible, laminar mixed convective fluid flow within two different types of tilted lid-driven trapezoidal enclosures filled with nanofluid composed of water and Al2O3 nanoparticles has been carried out in this paper. The upper wall of the enclosure is an isothermal cold surface that travels at a constant speed, while the bottom surface of the cavity maintains a constant high temperature. Non-dimensional governing equations along with the appropriate boundary conditions are solved using Galerkin finite element technique. Parametric simulation has been conducted by varying tilt angle of the base wall from 0° to 45°, Reynolds number from 0.1 to 10[3], Grashof number from 10[-2] to 10[6], and Richardson number between 0.1 and 10 for three different cases. The streamlines and the isotherms are used to describe the fluid flow and heat transfer characteristics within the enclosure. Besides, the quantitative evaluations of thermal enhancement in terms of the average Nusselt number, average fluid temperature, and Bejan number of the enclosure are presented. Effects of base wall tilt angle and the presence of nanofluid on convection heat transmission characteristics as well as Bejan number are also explored.}, } @article {pmid36506374, year = {2022}, author = {Hamza, NFA and Aljabair, S}, title = {Evaluation of thermal performance factor by hybrid nanofluid and twisted tape inserts in heat exchanger.}, journal = {Heliyon}, volume = {8}, number = {12}, pages = {e11950}, pmid = {36506374}, issn = {2405-8440}, abstract = {The thermal performance parameters of an improved heat exchanger tube fitted with various vortex generator inserts were investigated using numerical and experimental methods. The governing equations have been solved numerically by a Finite Volume approach employing the turbulence model (κ - ε). Two twisted tape types, which being inserted across a circular pipe (plain twisted tape) and (Double V-cut twisted tape), have been achieved. The hybrid nanofluid is prepared by using metal oxide [Al2O3+CuO] with distilled water at volume fraction range (0.6%, 1.2% and 1.8%), Reynolds number range (3560-8320) at twisted ratio (9.25). The experimental data for a plain tube, plain twisted tapes and double v-cut twisted tape are validated using the standard correlations available in the literature. The effect of such variables upon the average Nusselt number, friction factor, and thermal performance factor have been investigated and compared with a plain tube at the same conditions. As compared to plain twisted tape, the tube equipped with a double V-cut twisted tape with hybrid nanofluid displayed increased thermal performance. The greater vortex flow induced by the V-cuts results in more active thermal boundary layer disturbance, resulting in a greater heat transfer rate. The results show that thermal performance factor for hybrid nanofluid in plain circular tube at (∅ = 1.8 %) and Reynolds number (8320) is about (1.068), when the plain twisted tape and double v-cut twisted tape inserted with hybrid nanofluid the thermal performance factor increased to (1.33) and (1.37), respectively. The results show a similar trend for both numerical and experimental cases. The comparison between the experimental and numerical results have maximum error was (9.7)%.}, } @article {pmid36500800, year = {2022}, author = {Arshad, M and Hassan, A and Haider, Q and Alharbi, FM and Alsubaie, N and Alhushaybari, A and Burduhos-Nergis, DP and Galal, AM}, title = {Rotating Hybrid Nanofluid Flow with Chemical Reaction and Thermal Radiation between Parallel Plates.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {23}, pages = {}, pmid = {36500800}, issn = {2079-4991}, abstract = {This research investigates the two different hybrid nanofluid flows between two parallel plates placed at two different heights, y0 and yh, respectively. Water-based hybrid nanofluids are obtained by using Al2O3, TiO2 and Cu as nanoparticles, respectively. The upper-level plate is fixed, while the lower-level plate is stretchable. The fluid rotates along the y-axis. The governing equations of momentum, energy and concentration are transformed into partial differential equations by using similarity transformations. These transformed equations are grasped numerically at MATLAB by using the boundary value problem technique. The influence of different parameters are presented through graphs. The numerical outcomes for rotation, Nusselt, Prandtl, and Schmidt numbers are obtained in the form of tables. The heat transfer rate increases by augmentation in the thermophoresis parameter, while it decays by increasing the Reynolds number. Oxide nanoparticles hybrid nanofluid proved more efficient as compared to mixed nanoparticles hybrid nanofluid. This research suggests using oxide nanoparticles for good heat transfer.}, } @article {pmid36475799, year = {2022}, author = {Dong, C and Wang, L and Huang, YM and Comisso, L and Sandstrom, TA and Bhattacharjee, A}, title = {Reconnection-driven energy cascade in magnetohydrodynamic turbulence.}, journal = {Science advances}, volume = {8}, number = {49}, pages = {eabn7627}, pmid = {36475799}, issn = {2375-2548}, abstract = {Magnetohydrodynamic turbulence regulates the transfer of energy from large to small scales in many astrophysical systems, including the solar atmosphere. We perform three-dimensional magnetohydrodynamic simulations with unprecedentedly large magnetic Reynolds number to reveal how rapid reconnection of magnetic field lines changes the classical paradigm of the turbulent energy cascade. By breaking elongated current sheets into chains of small magnetic flux ropes (or plasmoids), magnetic reconnection leads to a previously undiscovered range of energy cascade, where the rate of energy transfer is controlled by the growth rate of the plasmoids. As a consequence, the turbulent energy spectra steepen and attain a spectral index of -2.2 that is accompanied by changes in the anisotropy of turbulence eddies. The omnipresence of plasmoids and their consequences on, for example, solar coronal heating, can be further explored with current and future spacecraft and telescopes.}, } @article {pmid36464577, year = {2023}, author = {Song, F and Yan, Y and Sun, J}, title = {Review of insect-inspired wing micro air vehicle.}, journal = {Arthropod structure & development}, volume = {72}, number = {}, pages = {101225}, doi = {10.1016/j.asd.2022.101225}, pmid = {36464577}, issn = {1873-5495}, mesh = {Animals ; *Aircraft ; Biomechanical Phenomena ; *Equipment Design ; Flight, Animal ; Insecta ; *Models, Biological ; Wings, Animal ; }, abstract = {Micro air vehicles (MAVs) have wide application prospects in environmental monitoring, disaster rescue and other civil fields because of their flexibility and maneuverability. Compared with fixed wing and rotary wing aircraft, flapping wing micro air vehicles (FWMAVs) have higher energy utilization efficiency and lower cost and have attracted extensive attention from scientists. Insects have become excellent bionic objects for the study of FWMAVs due to their characteristics of low Reynolds number, low noise, hoverability, small size and light weight. By mimicking flying insects, it may be possible to create highly efficient biomimetic FWMAVs. In this paper, insect flight aerodynamics are reviewed, and the mechanism designs of insect-inspired FWMAVs and their aerodynamics are summarized, including the wing type effect, vibration characteristics and aerodynamic characteristics of the flapping wing.}, } @article {pmid36462002, year = {2022}, author = {Jiang, H and Wang, D and Liu, S and Sun, C}, title = {Experimental Evidence for the Existence of the Ultimate Regime in Rapidly Rotating Turbulent Thermal Convection.}, journal = {Physical review letters}, volume = {129}, number = {20}, pages = {204502}, doi = {10.1103/PhysRevLett.129.204502}, pmid = {36462002}, issn = {1079-7114}, abstract = {What is the final state of turbulence when the driving parameter approaches infinity? For the traditional Rayleigh-Bénard convection, a possible ultimate scaling dependence of the heat transport (quantified by the Nusselt number Nu) on the Rayleigh number (Ra), which can be extrapolated to arbitrarily high Ra, is predicted by theories. The existence of the ultimate scaling has been intensively debated in the past decades. In this Letter, we adopt a novel supergravitational thermal convection experimental setup to study the possible transition to the ultimate regime. This system is characterized by the combined effects of radial-dependent centrifugal force, the Earth's gravity, and the Coriolis force. With an effective gravity up to 100 times the Earth's gravity, both Ra and shear Reynolds number can be boosted due to the increase of the buoyancy driving and the additional Coriolis forces. With over a decade of Ra range, we demonstrate the existence of ultimate regime with four direct evidences: the ultimate scaling dependence of Nu versus Ra; the appearance of the turbulent velocity boundary layer profile; the enhanced strength of the shear Reynolds number; and the new statistical properties of local temperature fluctuations. The present findings will greatly improve the understanding of the flow dynamics in geophysical and astrophysical flows.}, } @article {pmid36461968, year = {2022}, author = {Rorai, C and Toschi, F and Pagonabarraga, I}, title = {Coexistence of Active and Hydrodynamic Turbulence in Two-Dimensional Active Nematics.}, journal = {Physical review letters}, volume = {129}, number = {21}, pages = {218001}, doi = {10.1103/PhysRevLett.129.218001}, pmid = {36461968}, issn = {1079-7114}, abstract = {In active nematic liquid crystals, activity is able to drive chaotic spatiotemporal flows referred to as active turbulence. Active turbulence has been characterized through theoretical and experimental work as a low Reynolds number phenomenon. We show that, in two dimensions, the active forcing alone is able to trigger hydrodynamic turbulence leading to the coexistence of active and inertial turbulence. This type of flow develops for sufficiently active and extensile flow-aligning nematics. We observe that the combined effect of an extensile nematic and large values of the flow-aligning parameter leads to a broadening of the elastic energy spectrum that promotes a growth of kinetic energy able to trigger an inverse energy cascade.}, } @article {pmid36437305, year = {2022}, author = {Robles, V and Gonzalez-Parra, JC and Cuando-Espitia, N and Aguilar, G}, title = {The effect of scalable PDMS gas-entrapping microstructures on the dynamics of a single cavitation bubble.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {20379}, pmid = {36437305}, issn = {2045-2322}, support = {825115//Consejo Nacional de Ciencia y Tecnología/ ; }, abstract = {The effect of gas-entrapping polydimethylsiloxane (PDMS) microstructures on the dynamics of cavitation bubbles laser-induced next to the PDMS surface is investigated and compared against the cavitation dynamics next to a flat smooth boundary. Local pressure gradients produced by a cavitation bubble cause the air pockets entrapped in the PDMS microstructures to expand and oscillate, leading to a repulsion of the cavitation bubble. The microstructures were fabricated as boxed crevices via a simple and scalable laser ablation technique on cast acrylic, allowing for testing of variable structure sizes and reusable molds. The bubble dynamics were observed using high speed photography and the surrounding flows were visualized and quantified using particle tracking velocimetry. Smaller entrapped air pockets showed an enhanced ability to withstand deactivation at three stand-off distances and over 50 subsequent cavitation events. This investigation provides insight into the potential to direct the collapse of a cavitation bubble away from a surface to mitigate erosion or to enhance microfluidic mixing in low Reynolds number flows.}, } @article {pmid36429949, year = {2022}, author = {Luo, J and Ma, X and Wang, L and Zhang, B and Yang, X and Yue, T}, title = {The Influence of Short-Term Heavy Rainfall on Hydraulic Characteristics and Rill Formation in the Yuanmou Dry-Hot Valley.}, journal = {International journal of environmental research and public health}, volume = {19}, number = {22}, pages = {}, pmid = {36429949}, issn = {1660-4601}, mesh = {*Water Movements ; *Rain ; Geologic Sediments ; Soil ; Rivers ; }, abstract = {Rill erosion is one of the major environmental problems in the world; it is an important factor with regard to land degradation and has a serious impact on production and daily life in the region. The widely distributed Yuanmou group stratum promotes the development of rill erosion, whereby the strong time-concentrated rainfall and the alternating arid-humid climate prepare the ground for the development of rills in soils. Therefore, a study of the processes of slope rill erosion was carried out, and a gravel-soil slope in the Yuanmou dry-hot valley was chosen to simulate short-term heavy rainfall (25 mm/h) (No. 1 plot) and moderate rainfall (15 mm/h) (No. 2 plot), to study the erosion processes of soil and the dynamic characteristics of runoff involved in erosion. The study results showed that the width of runoff was significantly different between the two plots, while the depth of runoff was not significantly different. During the rill formation process, the width of the two plots first decreased and then increased with increasing washout duration, while its depth did not change significantly. Flow was the key factor in determining the hydraulic characteristics of runoff, and it had a significant or extremely significant positive correlation with hydraulic characteristics parameters, except in the case of Fr (Froude number) (r = 0.039). The total sediment content (CS) of plot No. 1 (0.158 g/cm[3]) was significantly different from that of plot No. 2 (0.153 g/cm[3]), and both CSs in the two plots decreased with increasing washout duration. The CS had an extremely significant negative correlation with τ (runoff shear force) (r = -0.863 **) and DW-f (Darcy-Weisbach drag coefficient) (r = -0.863 **) and a significant negative correlation with Re (Reynolds number) (r = -0.735 *) in the short-term heavy rainfall experiment, while the CS had a significant positive correlation with V (velocity) (r = 0.814 *), R (hydraulic radius) (r = 0.811 *) and P (unit stream power) (r = 0.811 *) in the moderate rainfall experiment. The results of this study will help guide further examination of the processes involved in the dynamic mechanisms of rill erosion on slopes under short-term heavy rainfall conditions.}, } @article {pmid36422415, year = {2022}, author = {Kumari, N and Alam, T and Ali, MA and Yadav, AS and Gupta, NK and Siddiqui, MIH and Dobrotă, D and Rotaru, IM and Sharma, A}, title = {A Numerical Investigation on Hydrothermal Performance of Micro Channel Heat Sink with Periodic Spatial Modification on Sidewalls.}, journal = {Micromachines}, volume = {13}, number = {11}, pages = {}, pmid = {36422415}, issn = {2072-666X}, abstract = {Electronic gadgets have been designed to incorporating very small components such as microcontrollers, electronic chips, transistors, microprocessors, etc. These components are exceptionally heat sensitive and can be wrecked if heat is not released. As a result, the thermal control of such components is critical to their optimum performance and extended life. The use of a microchannel heat sink (MCHS) has shown promising solutions to remove the excess heat. In this paper, we have proposed a novel design of MCHS and investigated it numerically. Four different surface modifications on the sidewall of the passage, namely, extended triangular surface (ETS), extended circular surface (ECS), triangular groove surface (TGS), and the circular groove surface (CGS) in the passage of the microchannel have been exploited in the Reynolds number of 100-900. In the presence of geometrical modification, the cooling capacities have been enhanced. The results show that the Nusselt numbers of ETS-MCHS, ECS-MCHS, TGS-MCHS, and CGS-MCHS are increased by 4.30, 3.61, 1.62, and 1.41 times in comparison to the Nusselt number of MCHS with smooth passage, while the friction factor values are increased by 7.33, 6.03, 2.74, and 1.68 times, respectively. In addition, the thermohydraulic performance parameter (THPP) has been evaluated and discussed. The fact that MCHS have THPP values greater than unity demonstrates that the passage's geometries are a practical means of achieving effective thermal management.}, } @article {pmid36411532, year = {2022}, author = {Toyama, K and Togi, F and Harada, S}, title = {Mass Transfer from Mobile to Immobile Regions in Irregularly Shaped Micro-Channels at Low Reynolds Number.}, journal = {Ground water}, volume = {}, number = {}, pages = {}, doi = {10.1111/gwat.13276}, pmid = {36411532}, issn = {1745-6584}, abstract = {Transient mass transfer in rough-walled micro-channels was investigated experimentally. We conducted experiments using rough-walled channels with various irregularities at small Reynolds number conditions. Mass transfer in the mainstream (mobile region) and dead water region (immobile region) were quantified using an image analysis technique based on absorption photometry. The experimental results showed that the solute dispersion in the mobile region was influenced by the irregular shape of the channel wall complicatedly. In contrast, mass transfer in the immobile region occurred by molecular diffusion independently on the wall roughness in our experimental conditions. The irregular shape of channel wall may enhance the mass transfer in mobile region by distorting the velocity distribution (Togi et al., 2020), while the solute redistribution to immobile region may suppress it in streamwise direction, just on a longer time scale. We developed a mass transfer model analogous to Mobile-Immobile model (MIM model) proposed by previous studies. The concept of the model is the same as the previous study (Zhou et al., 2019) and the coefficients of the model describing mass transfer in each region were quantified from the experimental results as functions of geometric characteristics of the rough-walled channel. In addition, mass transfer coefficient from mobile to immobile regions were derived mathematically based on the experimental results. The MIM model with the coefficients derived in this study well describes solute dispersion in variously shaped irregular channels quantitatively.}, } @article {pmid36405040, year = {2022}, author = {Kaziz, S and Ben Mariem, I and Echouchene, F and Belkhiria, M and Belmabrouk, H}, title = {Taguchi optimization of integrated flow microfluidic biosensor for COVID-19 detection.}, journal = {European physical journal plus}, volume = {137}, number = {11}, pages = {1235}, pmid = {36405040}, issn = {2190-5444}, abstract = {In this research, Taguchi's method was employed to optimize the performance of a microfluidic biosensor with an integrated flow confinement for rapid detection of the SARS-CoV-2. The finite element method was used to solve the physical model which has been first validated by comparison with experimental results. The novelty of this study is the use of the Taguchi approach in the optimization analysis. An L 8 2 7 orthogonal array of seven critical parameters-Reynolds number (Re), Damköhler number (Da), relative adsorption capacity (σ), equilibrium dissociation constant (KD), Schmidt number (Sc), confinement coefficient (α) and dimensionless confinement position (X), with two levels was designed. Analysis of variance (ANOVA) methods are also used to calculate the contribution of each parameter. The optimal combination of these key parameters was Re = 10[-2], Da = 1000, σ = 0.5, K D = 5, Sc = 10[5], α = 2 and X = 2 to achieve the lowest dimensionless response time (0.11). Among the all-optimization factors, the relative adsorption capacity (σ) has the highest contribution (37%) to the reduction of the response time, while the Schmidt number (Sc) has the lowest contribution (7%).}, } @article {pmid36399789, year = {2023}, author = {Jhun, CS and Xu, L and Siedlecki, C and Bartoli, CR and Yeager, E and Lukic, B and Scheib, CM and Newswanger, R and Cysyk, JP and Shen, C and Bohnenberger, K and Weiss, WJ and Rosenberg, G}, title = {Kinetic and Dynamic Effects on Degradation of von Willebrand Factor.}, journal = {ASAIO journal (American Society for Artificial Internal Organs : 1992)}, volume = {69}, number = {5}, pages = {467-474}, pmid = {36399789}, issn = {1538-943X}, support = {R01 HL136369/HL/NHLBI NIH HHS/United States ; }, mesh = {Humans ; von Willebrand Factor/metabolism ; *von Willebrand Diseases ; *Heart-Assist Devices ; Kinetics ; Molecular Weight ; }, abstract = {The loss of high molecular weight multimers (HMWM) of von Willebrand factor (vWF) in aortic stenosis (AS) and continuous-flow left ventricular assist devices (cf-LVADs) is believed to be associated with high turbulent blood shear. The objective of this study is to understand the degradation mechanism of HMWM in terms of exposure time (kinetic) and flow regime (dynamics) within clinically relevant pathophysiologic conditions. A custom high-shear rotary device capable of creating fully controlled exposure times and flows was used. The system was set so that human platelet-poor plasma flowed through at 1.75 ml/sec, 0.76 ml/sec, or 0.38 ml/sec resulting in the exposure time (texp) of 22, 50, or 100 ms, respectively. The flow was characterized by the Reynolds number (Re). The device was run under laminar (Re = 1,500), transitional (Re = 3,000; Re = 3,500), and turbulent (Re = 4,500) conditions at a given texp followed by multimer analysis. No degradation was observed at laminar flow at all given texp . Degradation of HMWM at a given texp increases with the Re. Re (p < 0.0001) and texp (p = 0.0034) are significant factors in the degradation of HMWM. Interaction between Re and texp , however, is not always significant (p = 0.73).}, } @article {pmid36399753, year = {2022}, author = {Bermudez, G and Alexakis, A}, title = {Saturation of Turbulent Helical Dynamos.}, journal = {Physical review letters}, volume = {129}, number = {19}, pages = {195101}, doi = {10.1103/PhysRevLett.129.195101}, pmid = {36399753}, issn = {1079-7114}, abstract = {The presence of large scale magnetic fields in nature is often attributed to the inverse cascade of magnetic helicity driven by turbulent helical dynamos. In this Letter, we show that in turbulent helical dynamos, the inverse flux of magnetic helicity toward the large scales Π_{H} is bounded by |Π_{H}|≤cεk_{η}^{-1}, where ε is the energy injection rate, k_{η} is the Kolmogorov magnetic dissipation wave number, and c an order one constant. Assuming the classical isotropic turbulence scaling, the inverse flux of magnetic helicity Π_{H} decreases at least as a -3/4 power law with the magnetic Reynolds number Rm: |Π_{H}|≤cεℓ_{f}Rm^{-3/4}max[Pm,1]^{1/4}, where Pm is the magnetic Prandtl number and ℓ_{f} the forcing length scale. We demonstrate this scaling with Rm using direct numerical simulations of turbulent dynamos forced at intermediate scales. The results further indicate that nonlinear saturation is achieved by a balance between the inverse cascade and dissipation at domain size scales L for which the saturation value of the magnetic energy is bounded by E_{m}≤cL(εℓ_{f})^{2/3}Rm^{1/4}max[1,Pm]^{1/4}. Numerical simulations also demonstrate this bound. These results are independent of the dynamo mechanism considered. In our setup, they imply that inviscid mechanisms cannot explain large scale magnetic fields and have critical implications for the modeling of astrophysical dynamos.}, } @article {pmid36397500, year = {2022}, author = {Budanur, NB and Kantz, H}, title = {Scale-dependent error growth in Navier-Stokes simulations.}, journal = {Physical review. E}, volume = {106}, number = {4-2}, pages = {045102}, doi = {10.1103/PhysRevE.106.045102}, pmid = {36397500}, issn = {2470-0053}, abstract = {We estimate the maximal Lyapunov exponent at different resolutions and Reynolds numbers in large eddy simulations (LES) and direct numerical simulations of sinusoidally driven Navier-Stokes equations in three dimensions. Independent of the Reynolds number when nondimensionalized by Kolmogorov units, the LES Lyapunov exponent diverges as an inverse power of the effective grid spacing showing that the fine scale structures exhibit much faster error growth rates than the larger ones. Effectively, i.e., ignoring the cutoff of this phenomenon at the Kolmogorov scale, this behavior introduces an upper bound to the prediction horizon that can be achieved by improving the precision of initial conditions through refining of the measurement grid.}, } @article {pmid36388976, year = {2022}, author = {Yao, N and Wang, H and Wang, B and Wang, X and Huang, J}, title = {Convective thermal cloaks with homogeneous and isotropic parameters and drag-free characteristics for viscous potential flows.}, journal = {iScience}, volume = {25}, number = {11}, pages = {105461}, pmid = {36388976}, issn = {2589-0042}, abstract = {Although convective thermal cloaking has been advanced significantly, the majority of related researches have concentrated on creeping viscous potential flows. Here, we consider convective thermal cloaking works in non-creeping viscous potential flows, and propose a combination of the separation of variables method and the equivalent-medium integral method to analytically deduce the parameters of convective thermal cloaks with isotropic-homogeneous dynamic viscosity and thermal conductivity. Through numerical simulation, we demonstrate the cloaks can hide the object from thermo-hydrodynamic fields. Besides, by comparing the drag force cloaks bear in cloak case and the objects bear in object-existent case, we find convective thermal cloaks can considerably reduce the drag force, which appears drag-free characteristics. Finally, it is our hope that these developed methods can reduce the difficulties of metadevices fabrications, promote the development of drag reduction technology under higher Reynolds number, and shed light on the control of other multi-physics systems.}, } @article {pmid36384832, year = {2022}, author = {Cao, BZ and Wang, J and Zhao, YJ and Liu, C}, title = {[Hydrodynamic characteristics of grass swale runoff in Guanzhong area of Loess Plateau, Northwest China.].}, journal = {Ying yong sheng tai xue bao = The journal of applied ecology}, volume = {33}, number = {11}, pages = {2979-2986}, doi = {10.13287/j.1001-9332.202211.023}, pmid = {36384832}, issn = {1001-9332}, mesh = {*Poaceae ; *Water Movements ; Hydrodynamics ; Rain ; Soil ; China ; }, abstract = {Grass swale has been widely used in sponge city construction, which can effectively improve the urban ecological environment. To explore the regulation mechanism of runoff in grass swale, runoff scouring experiment was carried out to study the hydrodynamic characteristics of runoff and the distribution of cross-section velocity under the combined conditions of five slopes (1%, 2%, 3%, 4%, 5%) and five scour flows (20, 30, 40, 50, 60 L·min[-1]). With the increases of flow rate and slope, flow velocity, Reynolds number and Froude number all increased gradually, while the Manning roughness coefficient and Darcy-Weisbach friction coefficient decreased gradually. The velocity (V) could be expressed as a power function V=0.3387Q[0.555]S[0.6601] of flow rate (Q) and slope (S). The variation ranges of Reynolds number and Froude number were 1160.95-6596.82 and 0.17-1.21, respectively. The runoff flow patterns were all turbulent. The flow pattern was greatly affected by the slope. When flow rate and slope were small, they had great influence on friction coefficient. Under the experimental conditions, the Darcy-Weisbach friction coefficient was negatively correlated with Reynolds number. The velocity distribution of cross-section showed symmetrical distribution on both sides of the center. The maximum velocity point was located at the center of water surface. With the increases of flow rate and slope, the velocity contours of cross section gradually became dense and the gradient of the velocity change increased. Our results provide a theoretical basis for the design, application and hydraulic calculation of grass swale in the construction of sponge cities in loess areas, and reveal the runoff regulation mechanism by analyzing the hydraulic characteristics of grass swale runoff.}, } @article {pmid36383261, year = {2022}, author = {Karami, A and Ranjbar, B and Rahimi, M and Mohammadi, F}, title = {Novel hybrid neuro-fuzzy model to anticipate the heat transfer in a heat exchanger equipped with a new type of self-rotating tube insert.}, journal = {The European physical journal. E, Soft matter}, volume = {45}, number = {11}, pages = {92}, pmid = {36383261}, issn = {1292-895X}, mesh = {*Hot Temperature ; *Algorithms ; Friction ; }, abstract = {In this investigation, a combination of the wingsuit flying search (WFS) and teaching-learning-based optimization (TLBO) algorithms is developed as a new combinatorial optimization algorithm. The proposed combinatorial algorithm is tested over some well-known benchmark functions and then integrated with the artificial neural network (ANN) to construct a novel hybrid model. After that, the obtained hybrid model is employed to anticipate the experimentally obtained values of the average Nusselt number (Nu), average friction coefficient (f) as well as thermal-hydraulic performance ratio (η), in a heat exchanger equipped with a new type of self-rotating tube insert, against governing parameters. The insert is placed in the tube side of the water heater to heat natural gas. The proposed insert consists of various numbers of self-rotating modules. Indeed, the rotating insert is introduced to create effective secondary sweeping flow on the inner side of the tube. Since this type of tube insert simultaneously provides heat transfer enhancement and undesired pressure drop, a thermal-hydraulic performance ratio is defined to consider both of them. The governing parameters are the number of inserts (0 ≤ N ≤ 30), reservoir's temperature (40 °C ≤ TR ≤ 50 °C) as well as Reynolds number (6 × 10[3] ≤ Re ≤ 18 × 10[3]). It was found that the WFS-TLBO enhances the effectiveness of the main ANN in anticipating the Nusselt number (Nu), average friction coefficient (f) as well as performance ratio (η). Moreover, introducing the WFS-TLBO algorithm into the neural network provides an enhancement in the effectiveness of the hybrid models based on the single WFS and TLBO algorithms in anticipating the same parameters.}, } @article {pmid36378533, year = {2022}, author = {Wei, SX and Yang, H and Au, CT and Xie, TL and Yin, SF}, title = {Mixing Characteristic and High-Throughput Synthesis of Cadmium Sulfide Nanoparticles with Cubic Hexagonal Phase Junctions in a Chaotic Millireactor.}, journal = {Langmuir : the ACS journal of surfaces and colloids}, volume = {38}, number = {47}, pages = {14439-14450}, doi = {10.1021/acs.langmuir.2c02087}, pmid = {36378533}, issn = {1520-5827}, abstract = {A four-stage oscillating feedback millireactor with splitters (S-OFM) was designed to improve the mixing performance based on chaotic advection. Three-dimensional CFD simulations were used to investigate its flow characteristics and mixing performance, and the generation mechanisms of secondary flows were examined. The results show that the mixing index (MIcup) increased with the increase in the Reynolds number (Re), and MIcup could reach 99.8% at Re = 663. Poincaré mapping and Kolmogorov entropy were adopted to characterize the chaotic advection intensity, which indicates that there is a intensity increase with the increase in Re. In addition, the results of Villermaux-Dushman experiments demonstrate that S-OFM performs excellently, and the mixing time could reach 1.04 ms at Re = 2764. Finally, S-OFM was successfully used to synthesize CdS nanoparticles with cubic hexagonal phase junctions. At a flow rate of 180 mL/min, the average particle size was 10.5 nm and the particle size distribution was narrow (with a coefficient of variation of 0.14).}, } @article {pmid36374705, year = {2022}, author = {Antunes, GC and Malgaretti, P and Harting, J and Dietrich, S}, title = {Pumping and Mixing in Active Pores.}, journal = {Physical review letters}, volume = {129}, number = {18}, pages = {188003}, doi = {10.1103/PhysRevLett.129.188003}, pmid = {36374705}, issn = {1079-7114}, abstract = {We show both numerically and analytically that a chemically patterned active pore can act as a micro- or nanopump for fluids, even if it is fore-aft symmetric. This is possible due to a spontaneous symmetry breaking which occurs when advection rather than diffusion is the dominant mechanism of solute transport. We further demonstrate that, for pumping and tuning the flow rate, a combination of geometrical and chemical inhomogeneities is required. For certain parameter values, the flow is unsteady, and persistent oscillations with a tunable frequency appear. Finally, we find that the flow exhibits convection rolls and hence promotes mixing in the low Reynolds number regime.}, } @article {pmid36374283, year = {2022}, author = {Hopkins, CC and Shen, AQ and Haward, SJ}, title = {Effect of blockage ratio on flow of a viscoelastic wormlike micellar solution past a cylinder in a microchannel.}, journal = {Soft matter}, volume = {18}, number = {46}, pages = {8856-8866}, pmid = {36374283}, issn = {1744-6848}, abstract = {We present experiments on the flow of a viscoelastic wormlike micellar solution around cylinders (radius R) confined in straight microchannels (width W). Thirteen flow geometries are tested where the blockage ratio is varied over a wide range 0.055 ≤ BR = 2R/W ≤ 0.63. Experiments are performed at negligible Reynolds number, and for Weissenberg numbers Wi = λU/R up to 1000, where U is the average flow speed and λ is the relaxation time of the fluid. Micro-particle image velocimetry is used to characterise the flow state at each BR and Wi. In all of the geometries, a first critical Weissenberg number marks a transition from symmetric flow to an asymmetric but time-steady flow state, while a second higher critical Weissenberg number marks the onset of time-dependent flows. However, we report a clear shift in behaviour over a narrow intermediate range of 0.33 ≲ BR ≲ 0.41. Channels with BR ≤ 0.33 fall in a 'low' BR regime, with instabilities that originate from the downstream stagnation point, while those with BR ≥ 0.44 fall in a 'high' BR regime, with instabilities developing at the upstream stagnation point. Behaviour within the newly-identified intermediate BR regime is complex due to the competing influence of the two stagnation points. We summarise all our results in a flow state diagram covering Wi-BR parameter space, clearly defining the different regimes of blockage ratio for the first time. Our results contribute to the understanding of the complexities of viscoelastic flow in this benchmark geometry.}, } @article {pmid36369608, year = {2023}, author = {Chen, Y and Feng, X and Shi, X and Cai, W and Li, B and Zhao, Y}, title = {Evaluation of computational fluid dynamics models for predicting pediatric upper airway airflow characteristics.}, journal = {Medical & biological engineering & computing}, volume = {61}, number = {1}, pages = {259-270}, pmid = {36369608}, issn = {1741-0444}, support = {IR2021211//harbin institute of technology/ ; }, mesh = {Humans ; Child ; *Hydrodynamics ; Computer Simulation ; *Larynx ; Trachea ; Respiration ; }, abstract = {Computational fluid dynamics (CFD) has the potential for use as a clinical tool to predict the aerodynamics and respiratory function in the upper airway (UA) of children; however, careful selection of validated computational models is necessary. This study constructed a 3D model of the pediatric UA based on cone beam computed tomography (CBCT) imaging. The pediatric UA was 3D printed for pressure and velocity experiments, which were used as reference standards to validate the CFD simulation models. Static wall pressure and velocity distribution inside of the UA under inhale airflow rates from 0 to 266.67 mL/s were studied by CFD simulations based on the large eddy simulation (LES) model and four Reynolds-averaged Navier-Stokes (RANS) models. Our results showed that the LES performed best for pressure prediction; however, it was much more time-consuming than the four RANS models. Among the RANS models, the Low Reynolds number (LRN) SST k-ω model had the best overall performance at a series of airflow rates. Central flow velocity determined by particle image velocimetry was 3.617 m/s, while velocities predicted by the LES, LRN SST k-ω, and k-ω models were 3.681, 3.532, and 3.439 m/s, respectively. All models predicted jet flow in the oropharynx. These results suggest that the above CFD models have acceptable accuracy for predicting pediatric UA aerodynamics and that the LRN SST k-ω model has the most potential for clinical application in pediatric respiratory studies.}, } @article {pmid36365668, year = {2022}, author = {de Araujo, MT and Furlan, L and Brandi, A and Souza, L}, title = {A Semi-Analytical Method for Channel and Pipe Flows for the Linear Phan-Thien-Tanner Fluid Model with a Solvent Contribution.}, journal = {Polymers}, volume = {14}, number = {21}, pages = {}, pmid = {36365668}, issn = {2073-4360}, support = {2013/07375-0//São Paulo Research Foundation/ ; 001//Coordenação de Aperfeicoamento de Pessoal de Nível Superior/ ; }, abstract = {This work presents a semi-analytical method for laminar steady-state channel and pipe flows of viscoelastic fluids using the Linear Phan-Thien-Tanner (LPTT) constitutive equation, with solvent viscosity contribution. For the semi-analytical method validation, it compares its results and two analytical solutions: the Oldroyd-B model and the simplified LPTT model (without solvent viscosity contribution). The results adopted different values of the dimensionless parameters, showing their influence on the viscoelastic fluid flow. The results include the distribution of the streamwise velocity component and the extra-stress tensor components in the wall-normal direction. In order to investigate the proposed semi-analytical method, different solutions were obtained, both for channel and pipe flows, considering different values of Reynolds number, solvent viscosity contribution in the homogeneous mixture, elongational parameter, shear parameter, and Weissenberg number. The results show that the proposed semi-analytical method can find a laminar solution using the non-Newtonian LPTT model with solvent viscosity contribution and verify the effect of the parameters in the resulting flow field.}, } @article {pmid36364597, year = {2022}, author = {Baig, MF and Chen, GM and Tso, CP}, title = {The Thermal Performance Analysis of an Al2O3-Water Nanofluid Flow in a Composite Microchannel.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {21}, pages = {}, pmid = {36364597}, issn = {2079-4991}, support = {FRGS/1/2019/TK03/MMU/02/1.//Ministry of Higher Education Malaysia/ ; }, abstract = {Partial filling of porous medium insert in a channel alleviates the tremendous pressure drop associated with a porous medium saturated channel, and enhances heat transfer at an optimum fraction of porous medium filling. This study pioneered an investigation into the viscous dissipative forced convective heat transfer in a parallel-plate channel, partially occupied with a porous medium at the core, under local thermal non-equilibrium condition. Solving the thermal energy equation along the Darcy-Brinkman equation, new exact temperature fields and Nusselt number are presented under symmetrical isoflux thermal boundary condition. Noteworthy is the heat flux bifurcation at the interface between the clear fluid and porous medium driven by viscous dissipation, in cases where the combined hydrodynamic resistance to fluid flow and thermal resistance to fluid conduction is considerable in low Darcy number porous medium insert. However, viscous dissipation does not affect the qualitative variation of the Nusselt number with the fraction of porous medium filling. By using Al2O3-Water nanofluid as the working fluid in a uniformly heated microchannel, partially filled with an optimum volume fraction of porous medium, the heat transfer coefficient improves as compared to utilizing water. The accompanied viscous dissipation however has a more adverse impact on the heat transfer coefficient of nanofluids with an increasing Reynolds number.}, } @article {pmid36363954, year = {2022}, author = {Chen, Z and Wang, Y and Zhou, S}, title = {Numerical Analysis of Mixing Performance in an Electroosmotic Micromixer with Cosine Channel Walls.}, journal = {Micromachines}, volume = {13}, number = {11}, pages = {}, pmid = {36363954}, issn = {2072-666X}, support = {51705184//National Natural Science Foundation of China/ ; GDZB-062//Program for Distinguished Talents of Six Domains in Jiangsu Province of China/ ; SJCX22_1671//Jiangsu Province Graduate Research and Practice Innovation Program Project/ ; }, abstract = {Micromixers have significant potential in the field of chemical synthesis and biological pharmaceuticals, etc. In this study, the design and numerical simulations of a passive micromixer and a novel active electroosmotic micromixer by assembling electrode pairs were both presented with a cosine channel wall. The finite element method (FEM) coupled with Multiphysics modeling was used. To propose an efficient micromixer structure, firstly, different geometrical parameters such as amplitude-to-wavelength ratio (a/c) and mixing units (N) in the steady state without an electric field were investigated. This paper aims to seek a high-quality mixing solution. Therefore, based on the optimization of the above parameters of the passive micromixer, a new type of electroosmotic micromixer with an AC electric field was proposed. The results show that the vortices generated by electroosmosis can effectively induce fluid mixing. The effects of key parameters such as the Reynolds number, the number of electrode pairs, phase shift, voltage, and electrode frequency on the mixing performance were specifically discussed through numerical analysis. The mixing efficiency of the electroosmotic micromixer is quantitatively analyzed, which can be achieved at 96%. The proposed micromixer has a simple structure that can obtain a fast response and high mixing index.}, } @article {pmid36363898, year = {2022}, author = {Dai, Y and Cha, H and Nguyen, NK and Ouyang, L and Galogahi, F and Yadav, AS and An, H and Zhang, J and Ooi, CH and Nguyen, NT}, title = {Dynamic Behaviours of Monodisperse Double Emulsion Formation in a Tri-Axial Capillary Device.}, journal = {Micromachines}, volume = {13}, number = {11}, pages = {}, pmid = {36363898}, issn = {2072-666X}, support = {DP220100261//Australian Research Council/ ; }, abstract = {We investigated experimentally, analytically, and numerically the formation process of double emulsion formations under a dripping regime in a tri-axial co-flow capillary device. The results show that mismatches of core and shell droplets under a given flow condition can be captured both experimentally and numerically. We propose a semi-analytical model using the match ratio between the pinch-off length of the shell droplet and the product of the core growth rate and its pinch-off time. The mismatch issue can be avoided if the match ratio is lower than unity. We considered a model with the wall effect to predict the size of the matched double emulsion. The model shows slight deviations with experimental data if the Reynolds number of the continuous phase is lower than 0.06 but asymptotically approaches good agreement if the Reynolds number increases from 0.06 to 0.14. The numerical simulation generally agrees with the experiments under various flow conditions.}, } @article {pmid36363842, year = {2022}, author = {Cao, M and Cao, S and Zhao, J and Zhu, J}, title = {Numerical Study of Thermal Enhancement in a Single- and Double-Layer Microchannel Heat Sink with Different Ribs.}, journal = {Micromachines}, volume = {13}, number = {11}, pages = {}, pmid = {36363842}, issn = {2072-666X}, abstract = {In this paper, a microchannel heat sink model was proposed to realize single- and double- layer flow through built-in ribs. The finite element volume method was used to analyze the influence of the length, thickness and angle of the inner rib on the flow and heat transfer characteristics of the microchannel heat sink. The pressure drop, temperature field, flow field, and thermal characteristics are given. The numerical simulation results show that the rectangular rib plate makes the fluid in the microchannel heat sink flow alternately in the upper and lower layers, which can effectively enhance heat transfer. However, with the increase in rib length, the comprehensive evaluation factor decreases. The change of the angle of the rectangular rib plate has little influence on the Nusselt number. The change rate of the comprehensive evaluation factor of the thickness of the rectangular rib plate is the largest. When the Reynolds number is 1724, the comprehensive evaluation factor of Case 9 is 4.7% higher than that of Case 2. According to the parameter study of the built-in rib plate, the optimal parameter combination is given, in which the angle is 0°, the length is 7.5 mm, and the thickness is 0.2-0.3 mm.}, } @article {pmid36363584, year = {2022}, author = {Cancilla, N and Tamburini, A and Tarantino, A and Visconti, S and Ciofalo, M}, title = {Friction and Heat Transfer in Membrane Distillation Channels: An Experimental Study on Conventional and Novel Spacers.}, journal = {Membranes}, volume = {12}, number = {11}, pages = {}, pmid = {36363584}, issn = {2077-0375}, abstract = {The results of an experimental investigation on pressure drop and heat transfer in spacer-filled plane channels, which are representative of Membrane Distillation units, are presented and discussed. Local and mean heat transfer coefficients were obtained by using Thermochromic Liquid Crystals and Digital Image Processing. The performances of a novel spacer geometry, consisting of spheres that are connected by cylindrical rods, and are hereafter named spheres spacers, were compared with those of more conventional woven and overlapped spacers at equal values of the Reynolds number Re (in the range ~150 to ~2500), the pitch-to-channel height ratio, the flow attack angle and the thermal boundary conditions (two-side heat transfer). For any flow rate, the novel spacer geometry provided the least friction coefficient and a mean Nusselt number intermediate between those of the overlapped and the woven spacers. For any pressure drop and for any pumping power, the novel spacer provided the highest mean Nusselt number over the whole Reynolds number range that was investigated. The influence of buoyancy was also assessed for the case of the horizontal channels. Under the experimental conditions (channel height H ≈ 1 cm, ΔT ≈ 10 °C), it was found to be large in empty (spacer-less) channels that were up to Re ≈ 1200 (corresponding to a Richardson number Ri of ~0.1), but it was much smaller and limited to the range Re < ~500 (Ri < ~0.5) in the spacer-filled channels.}, } @article {pmid36359756, year = {2022}, author = {Soulsbury, CD and Humphries, S}, title = {Biophysical Determinants and Constraints on Sperm Swimming Velocity.}, journal = {Cells}, volume = {11}, number = {21}, pages = {}, pmid = {36359756}, issn = {2073-4409}, mesh = {Animals ; Male ; *Sperm Motility ; *Semen ; Spermatozoa ; Biological Evolution ; Flagella ; }, abstract = {Over the last 50 years, sperm competition has become increasingly recognised as a potent evolutionary force shaping male ejaculate traits. One such trait is sperm swimming speed, with faster sperm associated with increased fertilisation success in some species. Consequently, sperm are often thought to have evolved to be longer in order to facilitate faster movement. However, despite the intrinsic appeal of this argument, sperm operate in a different biophysical environment than we are used to, and instead increasing length may not necessarily be associated with higher velocity. Here, we test four predictive models (ConstantPower Density, Constant Speed, Constant Power Transfer, Constant Force) of the relationship between sperm length and speed. We collated published data on sperm morphology and velocity from 141 animal species, tested for structural clustering of sperm morphology and then compared the model predictions across all morphologically similar sperm clusters. Within four of five morphological clusters of sperm, we did not find a significant positive relationship between total sperm length and velocity. Instead, in four morphological sperm clusters we found evidence for the Constant Speed model, which predicts that power output is determined by the flagellum and so is proportional to flagellum length. Our results show the relationship between sperm morphology (size, width) and swimming speed is complex and that traditional models do not capture the biophysical interactions involved. Future work therefore needs to incorporate not only a better understanding of how sperm operate in the microfluid environment, but also the importance of fertilising environment, i.e., internal and external fertilisers. The microenvironment in which sperm operate is of critical importance in shaping the relationship between sperm length and form and sperm swimming speed.}, } @article {pmid36351992, year = {2022}, author = {Abdizadeh, GR and Farokhinejad, M and Ghasemloo, S}, title = {Numerical investigation on the aerodynamic efficiency of bio-inspired corrugated and cambered airfoils in ground effect.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {19117}, pmid = {36351992}, issn = {2045-2322}, mesh = {Animals ; *Flight, Animal ; *Wings, Animal ; Models, Biological ; Computer Simulation ; }, abstract = {This research numerically investigates the flapping motion effect on the flow around two subsonic airfoils near a ground wall. Thus far, the aerodynamic efficiency of the dragonfly-inspired flapping airfoil has not been challenged by an asymmetric cambered airfoil considering the ground effect phenomenon, especially in the MAV flight range. The analysis is carried out on the basis of an unsteady Reynolds-averaged Navier-stokes (URANS) simulation, whereby the Transition SST turbulence model simulates the flow characteristics. Dragonfly-inspired and NACA4412 airfoils are selected in this research to assess the geometry effect on aerodynamic efficiency. Moreover, the impacts of Reynolds number (Re), Strouhal number (St), and average ground clearance of the flapping airfoil are investigated. The results indicate a direct relationship between the airfoil's aerodynamic performance ([Formula: see text]/[Formula: see text]) and the ground effect. The [Formula: see text]/[Formula: see text] increases by reducing the airfoil and ground distance, especially at [Formula: see text]. At [Formula: see text], by increasing the St from 0.2 to 0.6, the values of [Formula: see text]/[Formula: see text] decrease from 10.34 to 2.1 and 3.22 to 1.8 for NACA4412 and dragonfly airfoils, respectively. As a result, the [Formula: see text]/[Formula: see text] of the NACA4412 airfoil is better than that of the dragonfly airfoil, especially at low oscillation frequency. The efficiency difference between the two airfoils at St=0.6 is approximately 14%, indicating that the [Formula: see text]/[Formula: see text] difference decreases substantially with increasing frequency. For [Formula: see text], the results show the dragonfly airfoil to have better [Formula: see text]/[Formula: see text] in all frequencies than the NACA4412 airfoil.}, } @article {pmid36340085, year = {2022}, author = {Dang, J and Duan, X and Tian, S}, title = {Wall Effects for Spheroidal Particle in Confined Bingham Plastic Fluids.}, journal = {ACS omega}, volume = {7}, number = {43}, pages = {38717-38727}, pmid = {36340085}, issn = {2470-1343}, abstract = {The wall effects on the sedimentation motion of a single spheroidal particle in cylindrical tubes filled with Bingham plastic fluid are investigated with the fixed computational domain using the Computational Fluid Dynamic (CFD) model in steady-state mode. The CFD model is validated with literature in both bounded and unbounded mediums. The rheological model of the Bingham plastic fluid is regularized with a smoothly varying viscosity. The retardation effects of the tube wall are presented in functions of Reynolds number Re, radius ratio λ (the radius of the tube to the semiaxis of the particle normal to the flow λ = R/r), aspect ratio E (the ratio of the semiaxis of the particle along the flow to r, E = b/r), and Bingham number Bn. The simulation results demonstrate that the drag coefficient C D declines with the rise in Reynolds number. The relative contribution to drag coefficient from the pressure force increases with larger Bingham number comparing with that from the friction force. The formation and size of the recirculation wake is suppressed by the yield stress. While Bn is approaching infinity, the limiting behavior is observed in the location of yield surface and the value of yield-gravity parameter. The values of critical yield-gravity parameter are explicitly given at different values of E, showing independence with Re and λ. For the flow with Bn ≥ 100, the influence of wall can be even ignored while λ is larger than 5.}, } @article {pmid36337262, year = {2022}, author = {Rutledge, KM}, title = {Sniffing out Stingray Noses: The Functional Morphology of Batoid Olfaction.}, journal = {Integrative organismal biology (Oxford, England)}, volume = {4}, number = {1}, pages = {obac043}, pmid = {36337262}, issn = {2517-4843}, abstract = {Batoid fishes (rays, skates, sawfishes, and guitarfishes) are macrosmatic, meaning they rely on their sense of smell as one of the primary senses for survival and reproduction. Olfaction is important for long-distance tracking and navigation, predator and prey recognition, and conspecific signaling. However, the mechanisms by which batoids harness odorants is unknown. Without a direct pump-like system, it is hypothesized that batoids irrigate their nostrils via one or a combination of the following: the motion pump, buccopharyngeal pump, pressure (ex. pitot-like mechanism), or a shearing force (ex. viscous entrainment). These mechanisms rely on the size, shape, and position of the nostrils with respect to the head and to each other. Batoids are united as a group by their dorsoventrally compressed body plans, with nostrils on the ventral side of their body. This position presents several challenges for odor capture and likely limits the effectivity of the motion pump. Batoid fishes display an expansive nasal morphology, with inlet nostrils ranging from thin, vertical slits to wide, horizontal ovals to protruding, tube-like funnels, and more. In this paper, a morphometric model is developed to quantify the vast diversity in batoid nose shapes, sizes, and positions on the head in an ecological and functional framework. Specifically, swimming mode, lifestyle, habitat, and diet are examined for correlations with observed nasal morphotypes. Morphometric measurements were taken on all 4 orders present in Batoidea to broadly encompass batoid nasal diversity (Rhinopristiformes 4/5 families; Rajiformes 2/4 families; Torpediniformes 4/4 families; Myliobatiformes 8/11 families). All batoid external nasal diversity was found to be categorized into 5 major morphological groups and were termed: flush nare [circle, comma, intermediate], open nare, and protruding nare. Several morphometric traits remained significant when accounting for shared ancestry, including the position and angle of the nostril on the head, the width of the inlet hole, and the spacing of the nostrils from each other. These measurements were found to be closely correlated and statistically significant with the swimming mode of the animal. This study provides the first crucial step in understanding batoid olfaction, by understanding the diversity of the morphology of the system. Because odor capture is a strictly hydrodynamic process, it may be that factors relating more directly to the fluid dynamics (i.e., swimming mode, velocity, Reynolds number) may be more important in shaping the evolution of the diversity of batoid noses than other ecological factors like habitat and diet.}, } @article {pmid36332888, year = {2023}, author = {Saleem, T and Powell, T and Walker, W and Raju, S}, title = {Assessment of flow mechanics in the lower extremity venous system.}, journal = {Journal of vascular surgery. Venous and lymphatic disorders}, volume = {11}, number = {2}, pages = {365-372.e3}, doi = {10.1016/j.jvsv.2022.10.009}, pmid = {36332888}, issn = {2213-3348}, mesh = {Humans ; Female ; Young Adult ; Adult ; Middle Aged ; Male ; *Femoral Vein/diagnostic imaging ; *Vena Cava, Inferior/diagnostic imaging ; Iliac Vein/diagnostic imaging ; Leg/blood supply ; Ultrasonography ; }, abstract = {BACKGROUND: The Reynolds number (Re) is a dimensionless parameter that describes fluid flow mechanics. Veins are compliant and collapsible vascular conduits that can accommodate large volume changes in response to small pressure changes. However, only sparse information is available about flow parameters such as the Re in the venous system.

METHODS: Bilateral duplex ultrasound examination of 15 healthy volunteers (30 limbs) was performed before and after exercise (four flights of stairs) of the veins of the lower extremity (left and right sides) and inferior vena cava. These volunteers had been confirmed to not have any signs or symptoms of lower extremity venous disease via focused history and physical examination findings.

RESULTS: Most of the volunteers were women (73%). Their mean age was 37 ± 12.8 years. The Re was highest in the inferior vena cava among all the veins examined (470 ± 144 before exercise and 589 ± 205 after exercise; P = .04). The association between the change in Re before and after exercise and the specific vein examined was also significant for the right and left external iliac veins, right and left common femoral veins, right and left profunda femoris veins, right and left femoral veins, and right common iliac vein. Resistance and velocity maps for the lower extremity venous system were also created. The velocity increased and the resistance decreased as one moved up the venous tree toward the right atrium.

CONCLUSIONS: The Re increased for most of the lower extremity veins after exercise in our healthy volunteers. However, the critical value for turbulent flow was not reached despite the exercise.}, } @article {pmid36329077, year = {2022}, author = {Roósz, A and Rónaföldi, A and Svéda, M and Veres, Z}, title = {Effect of crucible wall roughness on the laminar/turbulent flow transition of the Ga75In25 alloy stirred by a rotating magnetic field.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {18592}, pmid = {36329077}, issn = {2045-2322}, support = {ANN 130946//Hungarian National Research, Development, and Innovation Office/ ; ANN 130946//Hungarian National Research, Development, and Innovation Office/ ; ANN 130946//Hungarian National Research, Development, and Innovation Office/ ; ANN 130946//Hungarian National Research, Development, and Innovation Office/ ; }, abstract = {The critical magnetic induction (Bcr) values of a melt flow produced by a rotating magnetic field (RMF), remaining laminar or turbulent, are essential in different solidification processes. In an earlier paper (Metall Res Technol 100: 1043-1061, 2003), we showed that Bcr depends on the crucible radius (R) and frequency of the magnetic field (f). The effect of wall roughness (WR) on Bcr was investigated in this study. Using ten different wall materials, we determined the angular frequency (ω) and Reynolds number (Re) as a function of the magnetic induction (B) and f using two different measuring methods (pressure compensation method, PCM; height measuring method, HMM). The experiments were performed at room temperature; therefore, the Ga75wt%In25wt% alloy was chosen for the experiments. Based on the measured and calculated results, a simple relationship was determined between Bcr and Re*, f, R, and WR, where the constants K1, K2, K3, and K4 depended on the physical properties of the melt and wall material:[Formula: see text].}, } @article {pmid36319372, year = {2022}, author = {Datta, R and Russell, DR and Tang, I and Clayson, T and Suttle, LG and Chittenden, JP and Lebedev, SV and Hare, JD}, title = {Time-resolved velocity and ion sound speed measurements from simultaneous bow shock imaging and inductive probe measurements.}, journal = {The Review of scientific instruments}, volume = {93}, number = {10}, pages = {103530}, doi = {10.1063/5.0098823}, pmid = {36319372}, issn = {1089-7623}, abstract = {We present a technique to measure the time-resolved velocity and ion sound speed in magnetized, supersonic high-energy-density plasmas. We place an inductive ("b-dot") probe in a supersonic pulsed-power-driven plasma flow and measure the magnetic field advected by the plasma. As the magnetic Reynolds number is large (RM > 10), the plasma flow advects a magnetic field proportional to the current at the load. This enables us to estimate the flow velocity as a function of time from the delay between the current at the load and the signal at the probe. The supersonic flow also generates a hydrodynamic bow shock around the probe, the structure of which depends on the upstream sonic Mach number. By imaging the shock around the probe with a Mach-Zehnder interferometer, we determine the upstream Mach number from the shock Mach angle, which we then use to determine the ion sound speed from the known upstream velocity. We use the sound speed to infer the value of Z̄Te, where Z̄ is the average ionization and Te is the electron temperature. We use this diagnostic to measure the time-resolved velocity and sound speed of a supersonic (MS ∼ 8), super-Alfvénic (MA ∼ 2) aluminum plasma generated during the ablation stage of an exploding wire array on the Magpie generator (1.4 MA, 250 ns). The velocity and Z̄Te measurements agree well with the optical Thompson scattering measurements reported in the literature and with 3D resistive magnetohydrodynamic simulations in GORGON.}, } @article {pmid36313190, year = {2022}, author = {Qiao, Y and Ma, Z and Onyango, C and Cheng, X and Dorfman, KD}, title = {DNA fragmentation in a steady shear flow.}, journal = {Biomicrofluidics}, volume = {16}, number = {5}, pages = {054109}, pmid = {36313190}, issn = {1932-1058}, abstract = {We have determined the susceptibility of T4 DNA (166 kilobase pairs, kbp) to fragmentation under steady shear in a cone-and-plate rheometer. After shearing for at least 30 min at a shear rate of 6000 s - 1 , corresponding to a Reynolds number of O (10 3) and a Weissenberg number of O (10 3) , 97.9 ± 1.3 % of the sample is broken into a polydisperse mixture with a number-averaged molecular weight of 62.6 ± 3.2 kbp and a polydispersity index of 1.29 ± 0.03 , as measured by pulsed-field gel electrophoresis (with a 95% confidence interval). The molecular weight distributions observed here from a shear flow are similar to those produced by a (dominantly extensional) sink flow of DNA and are qualitatively different than the midpoint scission observed in simple extensional flow. Given the inability of shear flow to produce a sharp coil-stretch transition, the data presented here support a model where polymers can be fragmented in flow without complete extension. These results further indicate that DNA fragmentation by shear is unlikely to be a significant issue in microfluidic devices, and anomalous molecular weight observations in experiments are due to DNA processing prior to observation in the device.}, } @article {pmid36301473, year = {2023}, author = {Bryan, MT}, title = {Assessing the Challenges of Nanotechnology-Driven Targeted Therapies: Development of Magnetically Directed Vectors for Targeted Cancer Therapies and Beyond.}, journal = {Methods in molecular biology (Clifton, N.J.)}, volume = {2575}, number = {}, pages = {105-123}, pmid = {36301473}, issn = {1940-6029}, mesh = {Humans ; *Neoplasms/genetics/therapy ; Nanotechnology ; Magnetics ; Drug Delivery Systems/methods ; Motion ; }, abstract = {Targeted delivery, in which therapeutic agents are preferentially concentrated at the diseased site, has the potential to improve therapeutic outcomes by minimizing off-target interactions in healthy tissue. Both passive and active methods of targeting delivery have been proposed, often with particular emphasis on cancer treatment. Passive methods rely on the overexpression of a biomarker in diseased tissue that can then be used to target the therapy. Active techniques involve physically guiding therapeutic agents toward the target region. Since the motion of magnetic particles can be remotely controlled by external magnetic fields, magnetic technologies have the potential to drive and hold drugs or other cargo at the required therapeutic site, increasing the localized dose while minimizing overall exposure. Directed motion may be generated either by simple magnetic attraction or by causing the particles to perform swimming strokes to produce propulsion. This chapter will compare the different strategies using magnetic nanotechnology to produce directed motion compatible with that required for targeted cargo delivery and magnetically assisted therapies and assess their potential to meet the challenges of operating within the human body.}, } @article {pmid36296816, year = {2022}, author = {Beck, J and Palmer, M and Inman, K and Wohld, J and Cummings, M and Fulmer, R and Scherer, B and Vafaei, S}, title = {Heat Transfer Enhancement in the Microscale: Optimization of Fluid Flow.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {20}, pages = {}, pmid = {36296816}, issn = {2079-4991}, abstract = {The focus of this paper is to investigate the effects of the addition of a connector between two serial microchannels. The idea of adding connector at the inlet of microchannels to enhance the random motion of molecules or nanoparticles in low Reynolds numbers was developed in our research group for the first time. It was experimentally determined that the shape of a connector between two microchannels has a significant impact on the enhancement of the random motion of molecules or nanoparticles. Consequently, the heat transfer coefficient is improved inside the second microchannel. The connector is large enough to refresh the memory of the fluid before entering the second channel, causing a higher maximum heat transfer coefficient in the second channel. It was also observed that the heat transfer coefficient can be increased at the end of the channel when the outlet temperature is relatively high. This may be explained by the fact that as temperature increases, the fluid viscosity tends to decrease, which generally drives an increase in the local random motion of base fluid molecules and nanoparticles. This causes an increase in the microchannel heat transfer coefficient. It was found that the addition of nanoparticles significantly modified the impact of the connector on the microchannel heat transfer coefficient. In addition, the effects of changing the Reynolds number and the shape of the connector were investigated through use of computational fluid dynamics (CFD) calculations. It was found that both factors have an important impact on the variation of velocity and enhancement of random motion of molecules and consequently significantly affect the heat transfer coefficient.}, } @article {pmid36296785, year = {2022}, author = {Chang, Q and Fu, Z and Zhang, S and Wang, M and Pan, X}, title = {Experimental Investigation of Reynolds Number and Spring Stiffness Effects on Vortex-Induced Vibration Driven Wind Energy Harvesting Triboelectric Nanogenerator.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {20}, pages = {}, pmid = {36296785}, issn = {2079-4991}, support = {51979045//National Natural Science Foundation of China/ ; }, abstract = {Vortex-induced vibration (VIV) is a process that wind energy converts to the mechanical energy of the bluff body. Enhancing VIV to harvest wind energy is a promising method to power wireless sensor nodes in the Internet of Things. In this work, a VIV-driven square cylinder triboelectric nanogenerator (SC-TENG) is proposed to harvest broadband wind energy. The vibration characteristic and output performance are studied experimentally to investigate the effect of the natural frequency by using five different springs in a wide range of stiffnesses (27 N/m

PURPOSE: To evaluate the effect of baseline blood flow rates and injection conditions on the extent of contrast reflux. To estimate arterial flow rates based on measurement of contrast reflux length.

MATERIALS AND METHODS: Iodinated contrast was injected into an idealized tube as well as a physiologically accurate model of the cervico-cerebral vasculature. A total of 194 high-speed angiograms were acquired under varying "blood" flow rates and injection conditions (catheter size, injection rate, and injection time). The length of contrast reflux was compared to the input variables and to dimensionless fluid dynamics parameters at the catheter-tip. Arterial blood flow rates were estimated using contrast reflux length as well as a traditional transit-time method and compared to measured flow rates.

RESULTS: Contrast reflux lengths were significantly affected by contrast injection rate (p < 0.0001), baseline blood flow rate (p = 0.0004), and catheter size (p = 0.04), but not by contrast injection time (p = 0.4). Reflux lengths were found to be correlated to dimensionless fluid dynamics parameters by an exponential function (R[2] = 0.6-0.99). When considering the entire dataset in unison, flow estimation errors with the reflux-length method (39% ± 33%) were significantly higher (p = 0.003) than the transit-time method (33% ± 36%). However, when subgrouped by catheter, the error with the reflux-length method was substantially reduced and was significantly lower (14% ± 14%, p < 0.0001) than the transit-time method.

CONCLUSION: Results show correlations between contrast reflux length and baseline hemodynamic parameters that have not been reported previously. Clinically relevant blood flow rate estimation is feasible by simple measurement of reflux length. In vivo and clinical studies are required to confirm these correlations and to refine the methodology of estimating blood flow by reflux.}, } @article {pmid36014668, year = {2022}, author = {Shi, R and Lin, J and Yang, H}, title = {Particle Distribution and Heat Transfer of SiO2/Water Nanofluid in the Turbulent Tube Flow.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {16}, pages = {}, pmid = {36014668}, issn = {2079-4991}, support = {12132015//National Natural Science Foundation of China/ ; }, abstract = {In order to clarify the effect of particle coagulation on the heat transfer properties, the governing equations of nanofluid together with the equation for nanoparticles in the SiO2/water nanofluid flowing through a turbulent tube are solved numerically in the range of Reynolds number 3000 ≤ Re ≤ 16,000 and particle volume fraction 0.005 ≤ φ ≤ 0.04. Some results are validated by comparing with the experimental results. The effect of particle convection, diffusion, and coagulation on the pressure drop ∆P, particle distribution, and heat transfer of nanofluid are analyzed. The main innovation is that it gives the effect of particle coagulation on the pressure drop, particle distribution, and heat transfer. The results showed that ∆P increases with the increase in Re and φ. When inlet velocity is small, the increase in ∆P caused by adding particles is relatively large, and ∆P increases most obviously compared with the case of pure water when the inlet velocity is 0.589 m/s and φ is 0.004. Particle number concentration M0 decreases along the flow direction, and M0 near the wall is decreased to the original 2% and decreased by about 90% in the central area. M0 increases with increasing Re but with decreasing φ, and basically presents a uniform distribution in the core area of the tube. The geometric mean diameter of particle GMD increases with increasing φ, but with decreasing Re. GMD is the minimum in the inlet area, and gradually increases along the flow direction. The geometric standard deviation of particle diameter GSD increases sharply at the inlet and decreases in the inlet area, remains almost unchanged in the whole tube, and finally decreases rapidly again at the outlet. The effects of Re and φ on the variation in GSD along the flow direction are insignificant. The values of convective heat transfer coefficient h and Nusselt number Nu are larger for nanofluids than that for pure water. h and Nu increase with the increase in Re and φ. Interestingly, the variation in φ from 0.005 to 0.04 has little effect on h and Nu.}, } @article {pmid36014601, year = {2022}, author = {Akram, S and Athar, M and Saeed, K and Razia, A and Alghamdi, M and Muhammad, T}, title = {Impact of Partial Slip on Double Diffusion Convection of Sisko Nanofluids in Asymmetric Channel with Peristaltic Propulsion and Inclined Magnetic Field.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {16}, pages = {}, pmid = {36014601}, issn = {2079-4991}, abstract = {The current article discusses the outcomes of the double diffusion convection of peristaltic transport in Sisko nanofluids along an asymmetric channel having an inclined magnetic field. Consideration is given to the Sisko fluid model, which can forecast both Newtonian and non-Newtonian fluid properties. Lubricating greases are the best examples of Sisko fluids. Experimental research shows that most realistic fluids, including human blood, paint, dirt, and other substances, correspond to Sisko's proposed definition of viscosity. Mathematical modelling is considered to explain the flow behavior. The simpler non-linear PEDs are deduced by using an elongated wavelength and a minimal Reynolds number. The expression is also numerically calculated. The impacts of the physical variables on the quantities of flow are plotted graphically as well as numerically. The results reveal that there is a remarkable increase in the concentration, temperature, and nanoparticle fraction with the rise in the Dufour and thermophoresis variables.}, } @article {pmid36001259, year = {2023}, author = {Canli, E and Kucuksariyildiz, H and Carman, K}, title = {Impact assessment of new generation high-speed agricultural tractor aerodynamics on transportation fuel consumption and related phenomena.}, journal = {Environmental science and pollution research international}, volume = {30}, number = {3}, pages = {6658-6680}, pmid = {36001259}, issn = {1614-7499}, mesh = {*Accidents, Occupational ; *Transportation ; Agriculture ; Carbon ; Gravitation ; }, abstract = {New generation agricultural tractors contribute to transportation by increased travel speeds. There is not any available aerodynamic data on the authentic agricultural tractor form. On-road transportation by tractors is between 8 and 30% of their operational time. In this work, two agricultural tractors are modelled via computational fluid dynamics for nine different speeds to determine aerodynamic resistances. Constant speed travel scenarios are analyzed. Corresponding speeds are 5 and 10 to 80 km/h with 10 km/h increments. Reynolds number changes between 1.6 × 10[5] and 2.98 × 10[6]. The characteristic lengths are taken as the square root of the streamwise projected area of the tractor geometries. Aerodynamic forces exerted on the tractors change between 3 and 746 N. The calculated drag coefficients are found as independent from Reynolds number and are 0.6 and 0.78 for the two different types of driver compartments. The approximated aerodynamic related fuel consumptions for 1-h changes between 0.002 and 8.28 lt/s which correspond to 0.001 to 5.76 kg/s carbon emission. A potential improvement in decreasing aerodynamic resistance about 20% is discussed by spatial data. Since the conducted work is being regarded as the first instance in the literature, it is estimated that several consecutive reports will be triggered.}, } @article {pmid35999194, year = {2022}, author = {Nan, K and Shi, Y and Zhao, T and Tang, X and Zhu, Y and Wang, K and Bai, J and Zhao, W}, title = {Mixing and Flow Transition in an Optimized Electrokinetic Turbulent Micromixer.}, journal = {Analytical chemistry}, volume = {94}, number = {35}, pages = {12231-12239}, doi = {10.1021/acs.analchem.2c02960}, pmid = {35999194}, issn = {1520-6882}, abstract = {Micromixer is a key element in a lab on a chip for broad applications in the analysis and measurement of chemistry and engineering. Previous investigations reported that electrokinetic (EK) turbulence could be realized in a "Y" type micromixer with a cross-sectional dimension of 100 μm order. Although the ultrafast turbulent mixing can be generated at a bulk flow Reynolds number on the order of unity, the micromixer has not been optimized. In this investigation, we systematically investigated the influence of electric field intensity, AC frequency, electric conductivity ratio, and channel width at the entrance on the mixing effect and transition electric Rayleigh number in the "Y" type electrokinetic turbulent micromixer. It is found that the optimal mixing is realized in a 350 μm wide micromixer, under 100 kHz and 1.14 × 10[5] V/m AC electric field, with an electric conductivity ratio of 1:3000. Under these conditions, a degree of mixedness of 0.93 can be achieved at 84 μm from the entrance and 100 ms. A further investigation of the critical electric field and the critical electric Rayleigh number indicates that the most unstable condition of EK flow instability is inconsistent with that of the optimal mixing in EK turbulence. To predict the evolution of EK flow under high Raσ and guide the design of EK turbulent micromixers, it is necessary to apply a computational turbulence model instead of linear instability analysis.}, } @article {pmid35990482, year = {2022}, author = {Mondal, T and Hnaien, N and Ajmi, M and Ghachem, K and Kolsi, L}, title = {CFD Investigation of Thermal Characteristics for a Dual Jet with a Parallel Co-flow.}, journal = {ACS omega}, volume = {7}, number = {32}, pages = {27864-27875}, pmid = {35990482}, issn = {2470-1343}, abstract = {A combined turbulent wall jet and offset jet (also known as the dual jet) with and without the presence of a parallel co-flow stream is studied. The standard k-ω turbulence model is used to predict the turbulent flow. The study focuses on the effects of the co-flow velocity (CFV) on the heat-transfer characteristics of the dual jet flow with the bottom wall maintained at a constant wall temperature. The CFV is varied up to 40% of the jet inlet velocity, and the height of the offset jet is varied from 5 to 11 times the jet width with the inlet Reynolds number taken as 15,000. The heat-transfer results reveal that the local Nusselt number (Nu x) along the bottom wall exhibits a peak at the immediate downstream of the nozzle exit, followed by a continuous decay in the rest of the converging region before showing a small rise for a short streamwise distance in the merging region. Further downstream, in the combined region, Nu x gradually decreases with the downstream distance. Except the merging region, no influence of co-flow is observed in the other two flow zones (converging and combined regions). In the merging region, for a given offset ratio (OR), Nu x remains nearly constant for a certain axial distance, and it decreases as the CFV increases. As a result of the increase in the CFV, the average Nusselt number decreases, indicating a reduction in overall convective heat transfer for higher values of the CFV. A regression analysis among the average Nusselt number (), CFV, and OR results in a correlation function in the form of within the range OR = 5-11 and CFV = 0-40%.}, } @article {pmid35965667, year = {2022}, author = {Wüthrich, D and Shi, R and Chanson, H}, title = {Hydraulic jumps with low inflow Froude numbers: air-water surface patterns and transverse distributions of two-phase flow properties.}, journal = {Environmental fluid mechanics (Dordrecht, Netherlands : 2001)}, volume = {22}, number = {4}, pages = {789-818}, pmid = {35965667}, issn = {1567-7419}, abstract = {ABSTRACT: Hydraulic jumps are commonly employed as energy dissipators to guarantee long-term operation of hydraulic structures. A comprehensive and in-depth understanding of their main features is therefore fundamental. In this context, the current study focused on hydraulic jumps with low Froude numbers, i.e. Fr1 = 2.1 and 2.4, at relatively high Reynolds number: Re ~2 × 10[5]. Experimental tests employed a combination of dual-tip phase-detection probes and ultra-high-speed video camera to provide a comprehensive characterisation of the main air-water flow properties of the hydraulic jump, including surface flow features, void fraction, bubble count rate and interfacial velocities. The current research also focused on the transverse distributions of air-water flow properties, i.e. across the channel width, with the results revealing lower values of void fraction and bubble count rate next to the sidewalls compared to the channel centreline data. Such a spatial variability in the transverse direction questions whether data near the side walls may be truly representative of the behaviour in the bulk of the flow, raising the issue of sidewall effects in image-based techniques. Overall, these findings provide new information to both researchers and practitioners for a better understanding of the physical processes inside the hydraulic jump with low Froude numbers, leading to an optimised design of hydraulic structures.

ARTICLE HIGHLIGHTS: Experimental investigation of air-water flow properties in hydraulic jumps with low Froude numbersDetailed description of the main air-water surface features on the breaking rollerTransversal distribution of the air-water flow properties across the channel width and comparison between centreline and sidewall.}, } @article {pmid35958096, year = {2022}, author = {Mohanty, RK and Setia, N and Khurana, G and Manchanda, G}, title = {High precision compact numerical approximation in exponential form for the system of 2D quasilinear elliptic BVPs on a discrete irrational region.}, journal = {MethodsX}, volume = {9}, number = {}, pages = {101790}, pmid = {35958096}, issn = {2215-0161}, abstract = {This article presents a new approximation of order four in exponential form for two-dimensional (2D) quasilinear partial differential equation (PDE) of elliptic form with solution domain being irrational. It is further extended for application to a system of quasilinear elliptic PDEs with Dirichlet boundary conditions (DBCs). The main highlights of the method framed in this article are as under:•It uses a 9-point stencil with unequal mesh to approach the solution. The error analysis is discussed to authenticate the order of convergence of the proposed numerical approximation.•Various validating problems, for instance the Burgers' equation, Poisson equation in cylindrical coordinates, Navier-Stokes (NS) equations in rectangular and cylindrical coordinates are solved using the proposed techniques to depict their stability. The proposed approximation produces solution free of oscillations for large values of Reynolds Number in the vicinity of a singularity.•The results of the proposed method are superior in comparison to the existing methods of [49] and [56].}, } @article {pmid35957150, year = {2022}, author = {Togun, H and Homod, RZ and Yaseen, ZM and Abed, AM and Dhabab, JM and Ibrahem, RK and Dhahbi, S and Rashidi, MM and Ahmadi, G and Yaïci, W and Mahdi, JM}, title = {Efficient Heat Transfer Augmentation in Channels with Semicircle Ribs and Hybrid Al2O3-Cu/Water Nanofluids.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {15}, pages = {}, pmid = {35957150}, issn = {2079-4991}, abstract = {Global technological advancements drive daily energy consumption, generating additional carbon-induced climate challenges. Modifying process parameters, optimizing design, and employing high-performance working fluids are among the techniques offered by researchers for improving the thermal efficiency of heating and cooling systems. This study investigates the heat transfer enhancement of hybrid "Al2O3-Cu/water" nanofluids flowing in a two-dimensional channel with semicircle ribs. The novelty of this research is in employing semicircle ribs combined with hybrid nanofluids in turbulent flow regimes. A computer modeling approach using a finite volume approach with k-ω shear stress transport turbulence model was used in these simulations. Six cases with varying rib step heights and pitch gaps, with Re numbers ranging from 10,000 to 25,000, were explored for various volume concentrations of hybrid nanofluids Al2O3-Cu/water (0.33%, 0.75%, 1%, and 2%). The simulation results showed that the presence of ribs enhanced the heat transfer in the passage. The Nusselt number increased when the solid volume fraction of "Al2O3-Cu/water" hybrid nanofluids and the Re number increased. The Nu number reached its maximum value at a 2 percent solid volume fraction for a Reynolds number of 25,000. The local pressure coefficient also improved as the Re number and volume concentration of "Al2O3-Cu/water" hybrid nanofluids increased. The creation of recirculation zones after and before each rib was observed in the velocity and temperature contours. A higher number of ribs was also shown to result in a larger number of recirculation zones, increasing the thermal performance.}, } @article {pmid35926485, year = {2022}, author = {Bhattacharjee, A and Jabbarzadeh, M and Kararsiz, G and Fu, HC and Kim, MJ}, title = {Bacteria-inspired magnetically actuated rod-like soft robot in viscous fluids.}, journal = {Bioinspiration & biomimetics}, volume = {17}, number = {6}, pages = {}, doi = {10.1088/1748-3190/ac870f}, pmid = {35926485}, issn = {1748-3190}, mesh = {Magnets ; Models, Biological ; *Robotics ; Swimming ; Viscosity ; }, abstract = {This paper seeks to design, develop, and explore the locomotive dynamics and morphological adaptability of a bacteria-inspired rod-like soft robot propelled in highly viscous Newtonian fluids. The soft robots were fabricated as tapered, hollow rod-like soft scaffolds by applying a robust and economic molding technique to a polyacrylamide-based hydrogel polymer. Cylindrical micro-magnets were embedded in both ends of the soft scaffolds, which allowed bending (deformation) and actuation under a uniform rotating magnetic field. We demonstrated that the tapered rod-like soft robot in viscous Newtonian fluids could perform two types of propulsion; boundary rolling was displayed when the soft robot was located near a boundary, and swimming was displayed far away from the boundary. In addition, we performed numerical simulations to understand the swimming propulsion along the rotating axis and the way in which this propulsion is affected by the soft robot's design, rotation frequency, and fluid viscosity. Our results suggest that a simple geometrical asymmetry enables the rod-like soft robot to perform propulsion in the low Reynolds number (Re≪ 1) regime; these promising results provide essential insights into the improvements that must be made to integrate the soft robots into minimally invasivein vivoapplications.}, } @article {pmid35918493, year = {2022}, author = {Xiao, L and Liu, Q and Huang, W}, title = {Experimental research and analysis on the resistance characteristics of simulated ore bin in water.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {13211}, pmid = {35918493}, issn = {2045-2322}, support = {51774193//National Natural Science Foundation of China/ ; ZR2017MEE025//Shandong Provincial Natural Science Foundation/ ; }, abstract = {In order to research the variation law of the longitudinal resistance coefficient of the ore bin in the marine mining system under different length-diameter ratio, external shape, additional weight and Reynolds number, a set of experimental system for testing the resistance coefficient was designed and built independently. By analyzing the experimental results, it can be seen that under the same conditions, the resistance coefficient decreases gradually with the increase of Reynolds number and finally fluctuates around a certain value. Increasing the excitation displacement will reduce the overall resistance coefficient of the ore bin. The smaller the length-diameter ratio is, the larger the corresponding force value when the vibration acceleration of the ore bin is 0, and the larger the overall resistance coefficient is. The resistance coefficient of the cylindrical section is greater than that of the rectangular shape. In order to reduce the longitudinal vibration and the transverse towing offset, the shape of the ore bin should be cylindrical in actual design and production. At low Reynolds number, the increase of added weight will increase the resistance coefficient, while at high Reynolds number, the change of added weight will not cause the change of resistance coefficient.}, } @article {pmid35912042, year = {2022}, author = {Ram, D and Bhandari, DS and Tripathi, D and Sharma, K}, title = {Propagation of H1N1 virus through saliva movement in oesophagus: a mathematical model.}, journal = {European physical journal plus}, volume = {137}, number = {7}, pages = {866}, pmid = {35912042}, issn = {2190-5444}, abstract = {H1N1 (Swine flu) is caused by the influenza A virus which belongs to the Orthomyxoviridae family. Influenza A is very harmful to the elderly, and people with chronic respiratory disease and cardiovascular disease. Therefore, it is essential to analyse the behaviour of virus transmission through the saliva movement in oesophagus. A mathematical paradigm is developed to study the saliva movement under the applications of transverse magnetic field. Jeffrey fluid model is considered for saliva to show the viscoelastic nature. The flow nature is considered creeping and assumptions of long wavelength and low Reynolds number are adopted for analytical solutions. The Basset-Boussinesq-Oseen equation is employed to understand the propagation of H1N1 virus through saliva under the effect of applicable forces such as gravity, virtual mass, basset force, and drag forces. The suitable data for saliva, oesophagus and H1N1 virus are taken from the existing literature for simulation of the results using MATLAB software. From the graphical results, it is observed that the susceptibility to viral infections is less because the magnetic field reduces the motion of the virus particle. Further, the chances of infections in males are more as compared to females and children due to variation in viscosity of saliva. Such findings provide an understanding of the mechanics of the virus floating through the saliva (viscoelastic fluids) in the oesophagus.}, } @article {pmid35912036, year = {2022}, author = {Strazzullo, M and Girfoglio, M and Ballarin, F and Iliescu, T and Rozza, G}, title = {Consistency of the full and reduced order models for evolve-filter-relax regularization of convection-dominated, marginally-resolved flows.}, journal = {International journal for numerical methods in engineering}, volume = {123}, number = {14}, pages = {3148-3178}, pmid = {35912036}, issn = {0029-5981}, abstract = {Numerical stabilization is often used to eliminate (alleviate) the spurious oscillations generally produced by full order models (FOMs) in under-resolved or marginally-resolved simulations of convection-dominated flows. In this article, we investigate the role of numerical stabilization in reduced order models (ROMs) of marginally-resolved, convection-dominated incompressible flows. Specifically, we investigate the FOM-ROM consistency, that is, whether the numerical stabilization is beneficial both at the FOM and the ROM level. As a numerical stabilization strategy, we focus on the evolve-filter-relax (EFR) regularization algorithm, which centers around spatial filtering. To investigate the FOM-ROM consistency, we consider two ROM strategies: (i) the EFR-noEFR, in which the EFR stabilization is used at the FOM level, but not at the ROM level; and (ii) the EFR-EFR, in which the EFR stabilization is used both at the FOM and at the ROM level. We compare the EFR-noEFR with the EFR-EFR in the numerical simulation of a 2D incompressible flow past a circular cylinder in the convection-dominated, marginally-resolved regime. We also perform model reduction with respect to both time and Reynolds number. Our numerical investigation shows that the EFR-EFR is more accurate than the EFR-noEFR, which suggests that FOM-ROM consistency is beneficial in convection-dominated, marginally-resolved flows.}, } @article {pmid35905362, year = {2022}, author = {Wang, X and Shih, HY and Goldenfeld, N}, title = {Stochastic Model for Quasi-One-Dimensional Transitional Turbulence with Streamwise Shear Interactions.}, journal = {Physical review letters}, volume = {129}, number = {3}, pages = {034501}, doi = {10.1103/PhysRevLett.129.034501}, pmid = {35905362}, issn = {1079-7114}, abstract = {The transition to turbulence in wall-bounded shear flows is typically subcritical, with a poorly understood interplay between spatial fluctuations, pattern formation, and stochasticity near the critical Reynolds number. Here, we present a spatially extended stochastic minimal model for the energy budget in transitional pipe flow, which successfully recapitulates the way localized patches of turbulence (puffs) decay, split, and grow, respectively, as the Reynolds number increases through the laminar-turbulent transition. Our approach takes into account the flow geometry, as we demonstrate by extending the model to quasi-one-dimensional Taylor-Couette flow, reproducing the observed directed percolation pattern of turbulent patches in space and time.}, } @article {pmid35899947, year = {2022}, author = {Godeau, AL and Leoni, M and Comelles, J and Guyomar, T and Lieb, M and Delanoë-Ayari, H and Ott, A and Harlepp, S and Sens, P and Riveline, D}, title = {3D single cell migration driven by temporal correlation between oscillating force dipoles.}, journal = {eLife}, volume = {11}, number = {}, pages = {}, pmid = {35899947}, issn = {2050-084X}, mesh = {*Actins/metabolism ; Cell Movement/physiology ; Cell Nucleus/metabolism ; *Cell Polarity/physiology ; Myosins/metabolism ; }, abstract = {Directional cell locomotion requires symmetry breaking between the front and rear of the cell. In some cells, symmetry breaking manifests itself in a directional flow of actin from the front to the rear of the cell. Many cells, especially in physiological 3D matrices, do not show such coherent actin dynamics and present seemingly competing protrusion/retraction dynamics at their front and back. How symmetry breaking manifests itself for such cells is therefore elusive. We take inspiration from the scallop theorem proposed by Purcell for micro-swimmers in Newtonian fluids: self-propelled objects undergoing persistent motion at low Reynolds number must follow a cycle of shape changes that breaks temporal symmetry. We report similar observations for cells crawling in 3D. We quantified cell motion using a combination of 3D live cell imaging, visualization of the matrix displacement, and a minimal model with multipolar expansion. We show that our cells embedded in a 3D matrix form myosin-driven force dipoles at both sides of the nucleus, that locally and periodically pinch the matrix. The existence of a phase shift between the two dipoles is required for directed cell motion which manifests itself as cycles with finite area in the dipole-quadrupole diagram, a formal equivalence to the Purcell cycle. We confirm this mechanism by triggering local dipolar contractions with a laser. This leads to directed motion. Our study reveals that these cells control their motility by synchronizing dipolar forces distributed at front and back. This result opens new strategies to externally control cell motion as well as for the design of micro-crawlers.}, } @article {pmid35896094, year = {2022}, author = {Zhang, JD and Sung, HJ and Huang, WX}, title = {Hydrodynamic interaction of dorsal fin and caudal fin in swimming tuna.}, journal = {Bioinspiration & biomimetics}, volume = {17}, number = {6}, pages = {}, doi = {10.1088/1748-3190/ac84b8}, pmid = {35896094}, issn = {1748-3190}, mesh = {*Animal Fins ; Animals ; Biomechanical Phenomena ; Hydrodynamics ; *Swimming ; Tuna ; }, abstract = {Tuna, which are known for high-performance swimming, possess a large crescent dorsal fin (DF) and a caudal fin (CF) that differ from those of other fishes. The hydrodynamic interaction between the DF and CF in tuna, which are represented by two tandem 3D flapping plates, is numerically explored in the present study. Hydrodynamic properties and wake structures of the models with and without a DF are compared to investigate the effects of the DF. The thrust on the CF is substantially enhanced by the DF, whereas the force on the DF is not affected by the CF. The constructive interaction between the leading-edge vortex (LEV) on the CF and the vortices shed from the dorsal fin (DFVs) is identified from 3D wake topology and 2D vorticity distributions. The circulation of spanwise vorticity quantitatively reveals that the LEV on the CF is strengthened by the same-signed DFV. The effect of the flapping phase of the CF is examined. The DF-CF interaction is sensitive to the flapping phase at a short spacing, whereas a long spacing between the two fins enables a robust constructive interaction in tuna swimming. A systematic study is carried out to explore the effects of the Strouhal number (St) and the Reynolds number (Re) on the interaction of the fins. The enhancement of thrust due to the DF is diminished at St = 0.63, whereas the Re does not substantially influence the constructive DF-CF interaction.}, } @article {pmid35892036, year = {2022}, author = {Mane, NS and Puri, DB and Mane, S and Hemadri, V and Banerjee, A and Tripathi, S}, title = {Separation of motile human sperms in a T-shaped sealed microchannel.}, journal = {Biomedical engineering letters}, volume = {12}, number = {3}, pages = {331-342}, pmid = {35892036}, issn = {2093-985X}, abstract = {UNLABELLED: Microfluidic methods act as an effective motile sperm separation technique used in infertility treatments. This work presents a standalone microfluidic device to separate motile sperm cells from non-motile sperm cells and debris. The separation mechanism is based on the centrifugal force acting on sperms and the ability of progressive motile sperms to swim upstream. The separation of motile sperm is carried out using a simple T-shaped microchannel which constitutes three reservoirs: one inlet and two outlets. Herein, one of the outlets is kept sealed. The sealed channel leads to a high-velocity gradient and a rheotaxis zone at the T junction resulting in the separation of motile sperms. Separated sperms are isolated in a sealed channel with a low Reynolds number flow so that sperms cannot have a net displacement, which ensures that the sperms do not re-enter the fluid flow. CFD simulation is conducted to study the flow fields inside the channel and experimental investigation is carried to observe the separation behaviour of sperms. The reported device provides 100% sperm separation efficiency and ensures the entrapment of sperm cells for a longer period. A modified colorimetric nitroblue tetrazolium test conducted on separated sperm cells shows that there is only a marginal increase in superoxide (O2 [-]) production, proving normal sperm integrity. This device offers an effective and safe alternative to conventional sperm sorting methods.

SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13534-022-00229-9.}, } @article {pmid35889690, year = {2022}, author = {Ghachem, K and Selimefendigil, F and Alshammari, BM and Maatki, C and Kolsi, L}, title = {Coupled Effects of Using Magnetic Field, Rotation and Wavy Porous Layer on the Forced Convection of Hybrid Nanoliquid Flow over 3D-Backward Facing Step.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {14}, pages = {}, pmid = {35889690}, issn = {2079-4991}, support = {PNURSP2022R41//Princess Nourah bint Abdulrahman University/ ; }, abstract = {In the present study, the effects of using a corrugated porous layer on the forced convection of a hybrid nanofluid flow over a 3D backward facing step are analyzed under the coupled effects of magnetic field and surface rotation. The thermal analysis is conducted for different values of the Reynolds number (Re between 100 and 500), the rotational Reynolds number (Rew between 0 and 2000), the Hartmann number (Ha between 0 and 15), the permeability of the porous layer (the Darcy number, Da between 10-5 and 10-2) and the amplitude (ax between 0.01 ap and 0.7 ap) and wave number (N between 1 and 16) of the porous layer corrugation. When rotations are activated, the average Nusselt number (Nu) and pressure coefficient values rise, while the increment of the latter is less. The increment in the average Nu is higher for the case with a higher permeability of the layer. When the corrugation amplitude and wave number are increased, favorable impacts of the average Nu are observed, but at the same time pressure coefficients are increased. Successful thermal performance estimations are made by using a neural-based modeling approach with a four input-two output system.}, } @article {pmid35889569, year = {2022}, author = {Minea, AA and El-Maghlany, WM and Massoud, EZ}, title = {Heat Transfer Analysis of Nanocolloids Based on Zinc Oxide Nanoparticles Dispersed in PEG 400.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {14}, pages = {}, pmid = {35889569}, issn = {2079-4991}, abstract = {Cooling and heating are extremely important in many industrial applications, while the thermal performance of these processes generally depends on many factors, such as fluid flow rate, inlet temperature, and many more. Hence, tremendous efforts are dedicated to the investigation of several parameters to reach an efficient cooling or heating process. The interest in adding nanoparticles in regular heat transfer fluids delivered new fluids to the market, the nanofluids. In this paper, a new nanoparticle-enhanced fluid based on polyethylene glycol with ZnO nanoparticles is considered and its hydrothermal performance is investigated for HVAC applications. The thermophysical properties of PEG 400-ZnO and their variation with temperature at different nanoparticle loading are previously determined on experimental bases and here implemented in a numerical application. The numerical results are completed at Reynolds number from 200 to 2000, while the nanoparticle concentration varies from 0.5 to 5%. Results are discussed in terms of Nusselt number, friction factor, and dimensionless pressure drop ratio at different temperatures and ZnO loading in the PEG 400 base fluid. Additionally, the evaluation performance criteria (EC) are calculated and discussed. Concluding, the newly developed fluid enhances the heat transfer up to 16% with a 13% pressure drop penalty, while the performance evaluation criteria are enhanced. Plus, several correlations are developed for both Nusselt number and friction factor as a function of relevant operating conditions.}, } @article {pmid35888927, year = {2022}, author = {Wang, Y and Yin, Z and Bao, F and Shen, J}, title = {CFD-DEM Coupling Model for Deposition Process Analysis of Ultrafine Particles in a Micro Impinging Flow Field.}, journal = {Micromachines}, volume = {13}, number = {7}, pages = {}, pmid = {35888927}, issn = {2072-666X}, abstract = {Gas with ultrafine particle impaction on a solid surface is a unique case of curvilinear motion that can be widely used for the devices of surface coatings or instruments for particle size measurement. In this work, the Eulerian-Lagrangian method was applied to calculate the motion of microparticles in a micro impinging flow field with consideration of the interactions between particle to particle, particle to wall, and particle to fluid. The coupling computational fluid dynamics (CFD) with the discrete element method (DEM) was employed to investigate the different deposition patterns of microparticles. The vortex structure and two types of particle deposits ("halo" and "ring") have been discussed. The particle deposition characteristics are affected both by the flow Reynolds number (Re) and Stokes number (stk). Moreover, two particle deposition patterns have been categorized in terms of Re and stk. Finally, the characteristics and mechanism of particle deposits have been analyzed using the particle inertia, the process of impinging (particle rebound or no rebound), vortical structures, and the kinetic energy conversion in two-phase flow, etc.}, } @article {pmid35888885, year = {2022}, author = {Zhou, Y and Dai, L and Jiao, N}, title = {Review of Bubble Applications in Microrobotics: Propulsion, Manipulation, and Assembly.}, journal = {Micromachines}, volume = {13}, number = {7}, pages = {}, pmid = {35888885}, issn = {2072-666X}, support = {Nos. 62127811, 91748212, 61821005//National Natural Science Foundation of China/ ; }, abstract = {In recent years, microbubbles have been widely used in the field of microrobots due to their unique properties. Microbubbles can be easily produced and used as power sources or tools of microrobots, and the bubbles can even serve as microrobots themselves. As a power source, bubbles can propel microrobots to swim in liquid under low-Reynolds-number conditions. As a manipulation tool, microbubbles can act as the micromanipulators of microrobots, allowing them to operate upon particles, cells, and organisms. As a microrobot, microbubbles can operate and assemble complex microparts in two- or three-dimensional spaces. This review provides a comprehensive overview of bubble applications in microrobotics including propulsion, micromanipulation, and microassembly. First, we introduce the diverse bubble generation and control methods. Then, we review and discuss how bubbles can play a role in microrobotics via three functions: propulsion, manipulation, and assembly. Finally, by highlighting the advantages and current challenges of this progress, we discuss the prospects of microbubbles in microrobotics.}, } @article {pmid35888870, year = {2022}, author = {Juraeva, M and Kang, DJ}, title = {Mixing Enhancement of a Passive Micromixer with Submerged Structures.}, journal = {Micromachines}, volume = {13}, number = {7}, pages = {}, pmid = {35888870}, issn = {2072-666X}, support = {BOKUK2022//BOKUK/ ; }, abstract = {A passive micromixer combined with two different mixing units was designed by submerging planar structures, and its mixing performance was simulated over a wider range of the Reynolds numbers from 0.1 to 80. The two submerged structures are a Norman window and rectangular baffles. The mixing performance was evaluated in terms of the degree of mixing (DOM) at the outlet and the required pressure load between inlet and outlet. The amount of submergence was varied from 30 μm to 70 μm, corresponding to 25% to 58% of the micromixer depth. The enhancement of mixing performance is noticeable over a wide range of the Reynolds numbers. When the Reynolds number is 10, the DOM is improved by 182% from that of no submergence case, and the required pressure load is reduced by 44%. The amount of submergence is shown to be optimized in terms of the DOM, and the optimum value is about 40 μm. This corresponds to a third of the micromixer depth. The effects of the submerged structure are most significant in the mixing regime of convection dominance from Re = 5 to 80. In a circular passage along the Norman window, one of the two Dean vortices burst into the submerged space, promoting mixing in the cross-flow direction. The submerged baffles in the semi-circular mixing units generate a vortex behind the baffles that contributes to the mixing enhancement as well as reducing the required pressure load.}, } @article {pmid35888205, year = {2022}, author = {Vatsa, A and Alam, T and Siddiqui, MIH and Ali, MA and Dobrotă, D}, title = {Performance of Microchannel Heat Sink Made of Silicon Material with the Two-Sided Wedge.}, journal = {Materials (Basel, Switzerland)}, volume = {15}, number = {14}, pages = {}, pmid = {35888205}, issn = {1996-1944}, abstract = {New designs of the microchannel with a two-sided wedge shape at the base were studied numerically. Five different wedge angles ranging from 3° to 15° were incorporated into the microchannel design. Simulation of this novel microchannel was carried out using Computational Fluid Dynamics (CFD). Three-dimensional models of the microchannel heat sink were created, discretized, and based on Navier-Stokes and energy equations; laminar numerical solutions were obtained for heat transfer and pressure drop. Flow characteristics of water as coolant in a microchannel were studied. It was observed that numerical results are in good agreement with experimental results. It was found that the Nusselt number and friction factor are significantly varied with the increase in Reynolds number. The Nusselt number varies in the following ranges of 5.963-8.521, 5.986-8.550, 6.009-8.568, 6.040-8.609, and 6.078-8.644 at 3°, 6°, 9°, 12°, and 15°, respectively. The microchannel with a wedge angle of 15° was found to be better in terms of Nusselt number and thermo-hydraulic performance. The enhancement in the Nusselt number is found as 1.017-1.036 for a wedge angle of 15°; however, friction factors do not show the perceptible values at distinct values of wedge angle. Moreover, the thermo-hydraulic performance parameters (THPP) were evaluated and found to be maximum in the range of 1.027-1.045 for a wedge angle of 15°. However, minimum THPP was found in the range of 1.005-1.0185 for a wedge angle of 3°.}, } @article {pmid35885078, year = {2022}, author = {Qi, T and Lin, J and Ouyang, Z}, title = {Hydrodynamic Behavior of Self-Propelled Particles in a Simple Shear Flow.}, journal = {Entropy (Basel, Switzerland)}, volume = {24}, number = {7}, pages = {}, pmid = {35885078}, issn = {1099-4300}, support = {12132015//National Natural Science Foundation of China/ ; }, abstract = {The hydrodynamic properties of a squirmer type of self-propelled particle in a simple shear flow are investigated using the immersed boundary-lattice Boltzmann method in the range of swimming Reynolds number 0.05 ≤ Res ≤ 2.0, flow Reynolds number 40 ≤ Rep ≤ 160, blocking rate 0.2 ≤ κ ≤ 0.5. Some results are validated by comparing with available other results. The effects of Res, Rep and κ on the hydrodynamic properties of squirmer are discussed. The results show that there exist four distinct motion modes for the squirmer, i.e., horizontal mode, attractive oscillation mode, oscillation mode, and chaotic mode. Increasing Res causes the motion mode of the squirmer to change from a constant tumbling near the centerline to a stable horizontal mode, even an oscillatory or appealing oscillatory mode near the wall. Increasing the swimming intensity of squirmer under the definite Res will induce the squirmer to make periodic and stable motion at a specific distance from the wall. Increasing Rep will cause the squirmer to change from a stable swimming state to a spiral motion or continuous rotation. Increasing κ will strengthen the wall's attraction to the squirmer. Increasing swimming intensity of squirmer will modify the strength and direction of the wall's attraction to the squirmer if κ remains constant.}, } @article {pmid35879876, year = {2022}, author = {Punyaratabandhu, N and Dechadilok, P and Triampo, W and Katavetin, P}, title = {Hydrodynamic model for renal microvascular filtration: Effects of physiological and hemodynamic changes on glomerular size-selectivity.}, journal = {Microcirculation (New York, N.Y. : 1994)}, volume = {29}, number = {8}, pages = {e12779}, doi = {10.1111/micc.12779}, pmid = {35879876}, issn = {1549-8719}, mesh = {Humans ; Hydrodynamics ; *Diabetic Nephropathies ; Models, Biological ; Hemodynamics/physiology ; *Hypertension ; Glomerular Filtration Rate/physiology ; }, abstract = {OBJECTIVE: The first step in renal urine formation is ultrafiltration across the glomerular barrier. The change in its nanostructure has been associated with nephrotic syndromes. Effects of physiological and hemodynamic factor alterations associated with diabetic nephropathy (DN) on glomerular permselectivity are examined through a mathematical model employing low-Reynolds-number hydrodynamics and hindered transport theory.

METHODS: Glomerular capillaries are represented as networks of cylindrical tubes with multilayered walls. Glomerular basement membrane (GBM) is a fibrous medium with bimodal fiber sizes. Epithelial slit fiber spacing follows a lognormal distribution based on reported electron micrographs with the highest resolution. Endothelial fenestrae are filled with fibers the size of glycosaminoglycans (GAGs). Effects of fiber-macromolecule steric and hydrodynamic interactions are included. Focusing on diabetic nephropathy, the physiological and hemodynamic factors employed in the computation are those reported for healthy humans and patients with early-but-overt diabetic nephropathy. The macromolecule concentration is obtained as a finite element solution of the convection-diffusion equation.

RESULTS: Computed sieving coefficients averaged along the capillary length agree well with ficoll sieving coefficients from studies in humans for most solute radii. GBM thickening and the loss of the slit diaphragm hardly affect glomerular permselectivity. GAG volume fraction reduction in the endothelial fenestrae, however, significantly increases macromolecule filtration. Increased renal plasma flow rate (RPF), glomerular hypertension, and reduction of lumen osmotic pressure cause a slight sieving coefficient decrease. These effects are amplified by an increased macromolecule size.

CONCLUSION: Our results indicate that glomerular hypertension and the reduction in the oncotic pressure decreases glomerular macromolecule filtration. Reduction of RPF and changes in the glomerular barrier structure associated with DN, however, increase the solute sieving. Damage to GAGs caused by hyperglycemia is likely to be the most prominent factor affecting glomerular size-selectivity.}, } @article {pmid35879342, year = {2022}, author = {Skotnicka-Siepsiak, A}, title = {Pressure distribution on a flat plate in the context of the phenomenon of the Coanda effect hysteresis.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {12687}, pmid = {35879342}, issn = {2045-2322}, abstract = {As a result of the Coanda effect, a symmetrical free jet will flow as an asymmetrical wall jet. At the same time, at the obstacle along which the flow is observed, the wall jet generates pressure distribution. In this study, the obstacle located at the diffuser outlet is a flat plate with a variable inclination angle. The article presents results of the study on pressure distributions on a flat plate with a variable angle of inclination. In the experiment, the Reynolds number ranged from 16,192 to 42,240. A fixed geometry diffuser (Witoszyński nozzle) with a height of 0.60 m, width of 0.02 m and outlet velocity of 11.33-29.57 m/s was used. A plate with a length of 1.00 m and a variable inclination angle was installed at the diffuser outlet. What is new, however, is that the presented results of the experimental research include the influence of the Coanda effect hysteresis on the pressure distribution on the plate. The article shows how pressure distributions change on the plate depending on whether the initial angle of inclination was 0° and was increased gradually in the course of the experiment until a detachment of the jet flowing from the plate was observed, or the initial angle of inclination was close to 90° in the primal state and as the angle of the plate inclination was decreased, the jet flowing towards the plate reached the state of attachment to the plate surface. The study demonstrated that for a turbulent jet, pressure distribution on a flat plate is determined not only by the plate's inclination angle, but also by the direction of its rotation.}, } @article {pmid35863190, year = {2022}, author = {Hatte, S and Pitchumani, R}, title = {Novel nonwetting solid-infused surfaces for superior fouling mitigation.}, journal = {Journal of colloid and interface science}, volume = {627}, number = {}, pages = {308-319}, doi = {10.1016/j.jcis.2022.06.155}, pmid = {35863190}, issn = {1095-7103}, mesh = {*Calcium Sulfate ; *Copper ; Lubricants ; }, abstract = {Fouling is a ubiquitous issue in several environmental and energy applications. Here we introduce novel nonwetting solid-infused surfaces (SIS) with superior anti-fouling characteristics that are durable than conventional nonwetting surfaces in a dynamic flow environment. A systematic study is presented to elucidate the fouling mitigation performance of SIS in comparison to lubricant-infused surface (LIS) and conventional smooth surface. Copper tubes with SIS, LIS or smooth inner walls are fabricated and subjected to accelerated calcium sulfate fouling in a flow fouling experimental setup. Fouling on the various surface types is quantified in terms of asymptotic fouling resistance, and the fundamental morphological differences in the interactions of the foulant and the various surface types are analyzed. Based on a systematic sweep of the parameter combinations using design of experiments and Taguchi analysis, an analytical dependence of asymptotic fouling resistance on the governing parameters namely, Reynolds number, foulant concentration and temperature is derived. The analytical model is shown to predict the asymptotic fouling resistance to within 20% accuracy with a 95% confidence. In addition, for the first time, the effects of shear durability on the fouling mitigation performance of LIS vis-à-vis SIS are studied. It is shown that the novel nonwetting SIS offers a robust option for superior fouling mitigation over LIS in the long run.}, } @article {pmid35859200, year = {2022}, author = {Pumm, AK and Engelen, W and Kopperger, E and Isensee, J and Vogt, M and Kozina, V and Kube, M and Honemann, MN and Bertosin, E and Langecker, M and Golestanian, R and Simmel, FC and Dietz, H}, title = {A DNA origami rotary ratchet motor.}, journal = {Nature}, volume = {607}, number = {7919}, pages = {492-498}, pmid = {35859200}, issn = {1476-4687}, support = {724261/ERC_/European Research Council/International ; }, mesh = {*DNA/chemistry ; *Facilitated Diffusion ; Hydrogen-Ion Concentration ; *Molecular Motor Proteins/chemistry/metabolism ; Motion ; Movement ; Osmolar Concentration ; Proton-Translocating ATPases/chemistry/metabolism ; Stochastic Processes ; Temperature ; Thermodynamics ; }, abstract = {To impart directionality to the motions of a molecular mechanism, one must overcome the random thermal forces that are ubiquitous on such small scales and in liquid solution at ambient temperature. In equilibrium without energy supply, directional motion cannot be sustained without violating the laws of thermodynamics. Under conditions away from thermodynamic equilibrium, directional motion may be achieved within the framework of Brownian ratchets, which are diffusive mechanisms that have broken inversion symmetry[1-5]. Ratcheting is thought to underpin the function of many natural biological motors, such as the F1F0-ATPase[6-8], and it has been demonstrated experimentally in synthetic microscale systems (for example, to our knowledge, first in ref. [3]) and also in artificial molecular motors created by organic chemical synthesis[9-12]. DNA nanotechnology[13] has yielded a variety of nanoscale mechanisms, including pivots, hinges, crank sliders and rotary systems[14-17], which can adopt different configurations, for example, triggered by strand-displacement reactions[18,19] or by changing environmental parameters such as pH, ionic strength, temperature, external fields and by coupling their motions to those of natural motor proteins[20-26]. This previous work and considering low-Reynolds-number dynamics and inherent stochasticity[27,28] led us to develop a nanoscale rotary motor built from DNA origami that is driven by ratcheting and whose mechanical capabilities approach those of biological motors such as F1F0-ATPase.}, } @article {pmid35854607, year = {2022}, author = {Bandak, D and Goldenfeld, N and Mailybaev, AA and Eyink, G}, title = {Dissipation-range fluid turbulence and thermal noise.}, journal = {Physical review. E}, volume = {105}, number = {6-2}, pages = {065113}, doi = {10.1103/PhysRevE.105.065113}, pmid = {35854607}, issn = {2470-0053}, abstract = {We revisit the issue of whether thermal fluctuations are relevant for incompressible fluid turbulence and estimate the scale at which they become important. As anticipated by Betchov in a prescient series of works more than six decades ago, this scale is about equal to the Kolmogorov length, even though that is several orders of magnitude above the mean free path. This result implies that the deterministic version of the incompressible Navier-Stokes equation is inadequate to describe the dissipation range of turbulence in molecular fluids. Within this range, the fluctuating hydrodynamics equation of Landau and Lifschitz is more appropriate. In particular, our analysis implies that both the exponentially decaying energy spectrum and the far-dissipation-range intermittency predicted by Kraichnan for deterministic Navier-Stokes will be generally replaced by Gaussian thermal equipartition at scales just below the Kolmogorov length. Stochastic shell model simulations at high Reynolds numbers verify our theoretical predictions and reveal furthermore that inertial-range intermittency can propagate deep into the dissipation range, leading to large fluctuations in the equipartition length scale. We explain the failure of previous scaling arguments for the validity of deterministic Navier-Stokes equations at any Reynolds number and we provide a mathematical interpretation and physical justification of the fluctuating Navier-Stokes equation as an "effective field theory" valid below some high-wave-number cutoff Λ, rather than as a continuum stochastic partial differential equation. At Reynolds number around a million, comparable to that in Earth's atmospheric boundary layer, the strongest turbulent excitations observed in our simulation penetrate down to a length scale of about eight microns, still two orders of magnitude greater than the mean free path of air. However, for longer observation times or for higher Reynolds numbers, more extreme turbulent events could lead to a local breakdown of fluctuating hydrodynamics.}, } @article {pmid35854520, year = {2022}, author = {Margazoglou, G and Biferale, L and Cencini, M and Gallavotti, G and Lucarini, V}, title = {Nonequilibrium ensembles for the three-dimensional Navier-Stokes equations.}, journal = {Physical review. E}, volume = {105}, number = {6-2}, pages = {065110}, doi = {10.1103/PhysRevE.105.065110}, pmid = {35854520}, issn = {2470-0053}, abstract = {At the molecular level fluid motions are, by first principles, described by time reversible laws. On the other hand, the coarse grained macroscopic evolution is suitably described by the Navier-Stokes equations, which are inherently irreversible, due to the dissipation term. Here, a reversible version of three-dimensional Navier-Stokes is studied, by introducing a fluctuating viscosity constructed in such a way that enstrophy is conserved, along the lines of the paradigm of microcanonical versus canonical treatment in equilibrium statistical mechanics. Through systematic simulations we attack two important questions: (a) What are the conditions that must be satisfied in order to have a statistical equivalence between the two nonequilibrium ensembles? (b) What is the empirical distribution of the fluctuating viscosity observed by changing the Reynolds number and the number of modes used in the discretization of the evolution equation? The latter point is important also to establish regularity conditions for the reversible equations. We find that the probability to observe negative values of the fluctuating viscosity becomes very quickly extremely small when increasing the effective Reynolds number of the flow in the fully resolved hydrodynamical regime, at difference from what was observed previously.}, } @article {pmid35854514, year = {2022}, author = {Choudhury, A and Samanta, A}, title = {Linear stability of a falling film over a heated slippery plane.}, journal = {Physical review. E}, volume = {105}, number = {6-2}, pages = {065112}, doi = {10.1103/PhysRevE.105.065112}, pmid = {35854514}, issn = {2470-0053}, abstract = {A detailed parametric study on the linear stability analysis of a three-dimensional thin liquid film flowing down a uniformly heated slippery inclined plane is carried out for disturbances of arbitrary wavenumbers, where the liquid film satisfies Newton's law of cooling at the film surface. A coupled system of boundary value problems is formulated in terms of the amplitudes of perturbation normal velocity and perturbation temperature, respectively. Analytical solution of the boundary value problems demonstrates the existence of three dominant modes, the so-called H mode, S mode, and P mode, where the S mode and P mode emerge due to the thermocapillary effect. It is found that the onset of instabilities for the H mode, S mode, and P mode reduces in the presence of wall slip and leads to a destabilizing influence. Numerical solution based on the Chebyshev spectral collocation method unveils that the finite wavenumber H-mode instability can be stabilized, but the S-mode instability and the finite wavenumber P-mode instability can be destabilized by increasing the value of the Marangoni number. On the other hand, the Biot number shows a dual role in the H-mode and S-mode instabilities. But the P-mode instability can be made stable with the increasing value of the Biot number and the decreasing values of the Marangoni number and the Prandtl number. Furthermore, the H-mode and S-mode instabilities become weaker, but the P-mode instability becomes stronger, with the increasing value of the spanwise wavenumber. In addition, the shear mode emerges in the numerical simulation when the Reynolds number is large, which can be destabilized slightly with the increasing value of the Marangoni number; however, it can be stabilized with the increasing value of the slip length and introducing the spanwise wavenumber to the infinitesimal perturbation.}, } @article {pmid35854482, year = {2022}, author = {Ishimoto, K and Moreau, C and Yasuda, K}, title = {Self-organized swimming with odd elasticity.}, journal = {Physical review. E}, volume = {105}, number = {6-1}, pages = {064603}, doi = {10.1103/PhysRevE.105.064603}, pmid = {35854482}, issn = {2470-0053}, abstract = {We theoretically investigate self-oscillating waves of an active material, which were recently introduced as a nonsymmetric part of the elastic moduli, termed odd elasticity. Using Purcell's three-link swimmer model, we reveal that an odd-elastic filament at low Reynolds number can swim in a self-organized manner and that the time-periodic dynamics are characterized by a stable limit cycle generated by elastohydrodynamic interactions. Also, we consider a noisy shape gait and derive a swimming formula for a general elastic material in the Stokes regime with its elasticity modulus being represented by a nonsymmetric matrix, demonstrating that the odd elasticity produces biased net locomotion from random noise.}, } @article {pmid35851297, year = {2022}, author = {Shahzad, H and Wang, X and Ghaffari, A and Iqbal, K and Hafeez, MB and Krawczuk, M and Wojnicz, W}, title = {Fluid structure interaction study of non-Newtonian Casson fluid in a bifurcated channel having stenosis with elastic walls.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {12219}, pmid = {35851297}, issn = {2045-2322}, mesh = {Arteries ; Blood Flow Velocity ; Computer Simulation ; Constriction, Pathologic ; *Hemodynamics ; Humans ; *Models, Cardiovascular ; Stress, Mechanical ; }, abstract = {Fluid-structure interaction (FSI) gained a huge attention of scientists and researchers due to its applications in biomedical and mechanical engineering. One of the most important applications of FSI is to study the elastic wall behavior of stenotic arteries. Blood is the suspension of various cells characterized by shear thinning, yield stress, and viscoelastic qualities that can be assessed by using non-Newtonian models. In this study we explored non-Newtonian, incompressible Casson fluid flow in a bifurcated artery with a stenosis. The two-dimensional Casson model is used to study the hemodynamics of the flow. The walls of the artery are supposed to be elastic and the stenosis region is constructed in both walls. Suitable scales are used to transform the nonlinear differential equations into a dimensionless form. The problem is formulated and discretized using Arbitrary Lagrangian-Eulerian (ALE) approach. The finite element method (FEM) technique is used to solve the system of equations, together with appropriate boundary conditions. The analysis is carried out for the Bingham number, Hartmann number, and Reynolds number. The graphical results of pressure field, velocity profile, and load on the walls are assessed and used to study the influence of hemodynamic effects on stenotic arteries, bifurcation region, and elastic walls. This study shows that there is an increase in wall shear stresses (WSS) with increasing values of Bingham number and Hartmann number. Also, for different values of the Bingham number, the load on the upper wall is computed against the Hartmann number. The result indicate that load at the walls increases as the values of Bingham number and Hartmann number increase.}, } @article {pmid35820476, year = {2022}, author = {Zhao, X and Zuo, H and Jia, G}, title = {Effects of the continuous pulsation regeneration on the soot combustion in diesel particulate filter for heavy-duty truck.}, journal = {Chemosphere}, volume = {306}, number = {}, pages = {135651}, doi = {10.1016/j.chemosphere.2022.135651}, pmid = {35820476}, issn = {1879-1298}, mesh = {Dust ; Motor Vehicles ; *Soot/analysis ; Temperature ; *Vehicle Emissions/analysis ; }, abstract = {Continuous pulsation regeneration combustion of soot is employed for sine and cosine simulation study. Data showed that pressure uniformity of sine condition is better than that of cosine condition with the maximum pressure difference of 4353.5 Pa under the same simulation boundary conditions. The maximum regeneration temperature under cosine pressure is 46.12 K which is higher than that in sine form. Regeneration combustion reaction zone tends to be more stable laminar flow and Reynolds number of sine condition is 435.23 less than that of under cosine condition. The maximum Stanton number of cosine pressure condition is 3.67 and that of sine pressure condition is 5.15, which investigates heat transfer capacity of the sine pressure condition is better than that of the pressure of cosine form. The regeneration efficiency of inlet gradually increased from the minimum regeneration efficiency 74.18%-88.45% of sine and cosine. The soot under both pressure forms has achieved complete regeneration and the regeneration efficiency has exceeded 88% of porous medium filter body section. The soot regeneration combustion efficiency of the porous media filter section and outlet section is more sufficient under sine condition and the heat carried by the fluid can maintain the soot regeneration.}, } @article {pmid35811899, year = {2022}, author = {Sun, R and Chen, P and Li, L and Liu, Y and Zhai, X}, title = {Experimental Investigation of the Combustion Behavior of Transformer Oil Jet Flame.}, journal = {ACS omega}, volume = {7}, number = {26}, pages = {22969-22976}, pmid = {35811899}, issn = {2470-1343}, abstract = {Transformer oil jet fire is one of the most dangerous types of fires in substations. The combustion behavior of transformer oil jet fire produces uncontrollable hazards to personnel and equipment and even triggers a domino effect. However, the jet fire combustion behavior of such materials as transformer oil has not been revealed before. Investigation of the combustion behavior of transformer oil jet fire has positive implications for the prevention and control of substation fires. In this paper, KI25X transformer oil was used as fuel. A series of transformer oil jet fire experiments were conducted with variable orifice diameters (5, 10, and 15 mm) with heat release rates ranging from 200 to 659.2 kW. The results showed that the entrainment coefficient of transformer oil jet fire was greater than that of pure gas phase jet fire. The entrainment coefficient of transformer oil jet fire was 0.029. Using dimensionless theory, it was proposed that the imaginary point source was proportional to the 0.317 power of Froude number. Based on the point source model, a dimensional analysis model with Reynolds number was developed. The radiation fraction of transformer oil jet fire was proportional to the -0.133 power of Reynolds number. This study played an important role in improving the jet combustion behavior of transformer oil.}, } @article {pmid35787191, year = {2022}, author = {Jamshed, W and Safdar, R and Rehman, Z and Lashin, MMA and Ehab, M and Moussa, M and Rehman, A}, title = {Computational technique of thermal comparative examination of Cu and Au nanoparticles suspended in sodium alginate as Sutterby nanofluid via extending PTSC surface.}, journal = {Journal of applied biomaterials & functional materials}, volume = {20}, number = {}, pages = {22808000221104004}, doi = {10.1177/22808000221104004}, pmid = {35787191}, issn = {2280-8000}, mesh = {*Alginates ; Copper ; Gold ; Hot Temperature ; *Metal Nanoparticles ; }, abstract = {Current research underscores entropy investigation in an infiltrating mode of Sutterby nanofluid (SNF) stream past a dramatically expanding flat plate that highlights Parabolic Trough Solar Collector (PTSC). Satisfactory likeness factors are utilized to change halfway differential conditions (PDEs) to nonlinear conventional differential conditions (ODEs) along with relating limit requirements. A productive Keller-box system is locked in to achieve approximated arrangement of decreased conventional differential conditions. In the review, two sorts of nanofluids including Copper-sodium alginate (Cu-SA) and Gold-sodium alginate (Au-SA) are dissected. Results are graphically plotted as well as talked about in actual viewpoints. As indicated by key discoveries, an improvement in Brinkmann, as well as Reynolds number, brings about expanding the general framework entropy. Sutterby nanofluid boundary improves heat rate in PTSC. Additionally, Copper-sodium alginate nanofluid is detected as a superior thermal conductor than Gold-sodium alginate nanofluid. Further to that, the reported breakthroughs are beneficial to updating extremely bright lighting bulbs, heating and cooling machinery, ﬁber required to generate light, power production, numerous boilers, and other similar technologies.}, } @article {pmid35771996, year = {2022}, author = {Saro-Cortes, V and Cui, Y and Dufficy, T and Boctor, A and Flammang, BE and Wissa, AW}, title = {An Adaptable Flying Fish Robotic Model for Aero- and Hydrodynamic Experimentation.}, journal = {Integrative and comparative biology}, volume = {}, number = {}, pages = {}, doi = {10.1093/icb/icac101}, pmid = {35771996}, issn = {1557-7023}, abstract = {Flying fishes (family Exocoetidae) are known for achieving multi-modal locomotion through air and water. Previous work on understanding this animal's aerodynamic and hydrodynamic nature has been based on observations, numerical simulations, or experiments on preserved dead fish, and has focused primarily on flying pectoral fins. The first half of this paper details the design and validation of a modular flying fish inspired robotic model organism (RMO). The second half delves into a parametric aerodynamic study of flying fish pelvic fins, which to date have not been studied in-depth. Using wind tunnel experiments at a Reynolds number of 30,000, we investigated the effect of the pelvic fin geometric parameters on aerodynamic efficiency and longitudinal stability. The pelvic fin parameters investigated in this study include the pelvic fin pitch angle and its location along the body. Results show that the aerodynamic efficiency is maximized for pelvic fins located directly behind the pectoral fins and is higher for more positive pitch angles. In contrast, pitching stability is neither achievable for positive pitching angles nor pelvic fins located directly below the pectoral fin. Thus, there is a clear a trade-off between stability and lift generation, and an optimal pelvic fin configuration depends on the flying fish locomotion stage, be it gliding, taxiing, or taking off. The results garnered from the RMO experiments are insightful for understanding the physics principles governing flying fish locomotion and designing flying fish inspired aerial-aquatic vehicles.}, } @article {pmid35764779, year = {2022}, author = {Wu, YK and Liu, YP and Sun, M}, title = {Aerodynamics of two parallel bristled wings in low Reynolds number flow.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {10928}, pmid = {35764779}, issn = {2045-2322}, mesh = {Animals ; Biomechanical Phenomena ; *Flight, Animal/physiology ; Insecta/physiology ; Models, Biological ; *Wings, Animal/physiology ; }, abstract = {Most of the smallest flying insects use bristled wings. It was observed that during the second half of their upstroke, the left and right wings become parallel and close to each other at the back, and move upward at zero angle of attack. In this period, the wings may produce drag (negative vertical force) and side forces which tend to push two wings apart. Here we study the aerodynamic forces and flows of two simplified bristled wings experiencing such a motion, compared with the case of membrane wings (flat-plate wings), to see if there is any advantage in using the bristled wings. The method of computational fluid dynamics is used in the study. The results are as follows. In the motion of two bristled wings, the drag acting on each wing is 40% smaller than the case of a single bristled wing conducting the same motion, and only a very small side force is produced. But in the case of the flat-plate wings, although there is similar drag reduction, the side force on each wing is larger than that of the bristled wing by an order of magnitude (the underlying physical reason is discussed in the paper). Thus, if the smallest insects use membrane wings, their flight muscles need to overcome large side forces in order to maintain the intended motion for less negative lift, whereas using bristled wings do not have this problem. Therefore, the adoption of bristled wings can be beneficial during upward movement of the wings near the end of the upstroke, which may be one reason why most of the smallest insects adopt them.}, } @article {pmid35755331, year = {2022}, author = {Huang, X and Wang, Y and Wang, L and Yu, G and Wang, F}, title = {Effect of Structural Optimization of Scrubbing Cooling Rings on Vertical Falling Film Flow Characteristics.}, journal = {ACS omega}, volume = {7}, number = {24}, pages = {21291-21305}, pmid = {35755331}, issn = {2470-1343}, abstract = {In order to study the influence of the structural optimization of the scrubbing cooling ring in the scrubbing cooling chamber on the flow characteristics of the vertical falling film, the flow characteristics of the turbulent falling film in the rising section of the development region at different internal platform heights of the scrubbing cooling ring and a high Reynolds number were studied by FLUENT software. First, the correctness of the model was verified by the maximum error of simulation and experimental results of no more than 9.836%. Then, the distribution of liquid film thickness (δ), velocity (V), and turbulence intensity (I z) at 0° of the tube in the axial direction x = 0-500 mm were calculated and obtained when the platform height (H) was 0-30 mm and the liquid film Reynolds number (Re l) = 1.1541 × 10[4]-3.4623 × 10[4]. The results showed that δ in the entrance region increased sharply due to the "jet" effect with solid wall constraints formed by the structure of the water inlet pipe and the scrubbing cooling ring. On the contrary, the liquid film in the fully developed region showed a stable fluctuation trend due to the weakening of the "jet" effect. When H = 30 mm, the change of δ was relatively stable and the change of I z was small, indicating that this platform height is conducive to the stable and uniform distribution of the liquid film. In addition, when Re l < 1.1541 × 10[4], the liquid film was unstable due to the low flow rate and insufficient cohesion of the liquid film, but V increased slightly. In addition, with the increase of Re l, δ did not change significantly along the axial direction, that is, the Plateau-Rayleigh hindered the growth of δ. Finally, the empirical formula for δ applicable to Re l = 1.1541 × 10[4]-3.4623 × 10[4] at the axial fixed position was fitted for the first time.}, } @article {pmid35751170, year = {2022}, author = {Ducos, S and Pugliese, S and Demolliens, M and Beraud, L and Boussard, A and Delmas, A and Agostini, S and Garcia, J and Aiello, A and Durieux, EDH}, title = {Ontogeny of swimming performance of hatchery-reared post-larvae and juvenile fish: a case of two threatened Mediterranean species.}, journal = {Journal of fish biology}, volume = {101}, number = {4}, pages = {846-856}, pmid = {35751170}, issn = {1095-8649}, support = {//European Regional Fund FEDER 2017-2020/ ; //National funding CPER 2020-2022/ ; //Territorial collectivity of Corsica (CdC)/ ; }, mesh = {Animals ; *Endangered Species ; Fishes/physiology ; Larva/physiology ; *Perciformes/physiology ; *Swimming/physiology ; }, abstract = {Swimming performance is a well-established key physiological parameter of fish that is highly linked to their fitness in the wild. In the context of fish restocking purposes, it therefore appears crucial to study this specific behaviour. Here, the authors investigated intra and interspecies differences in the swimming performance of hatchery-reared post-larvae and juveniles belonging to two Mediterranean candidate threatened species, the common dentex, Dentex dentex (Sparidae), and the brown meagre, Sciaena umbra (Sciaenidae), with body sizes ranging from 8 to 37 mm total length (TL, from 24 to 58 days post-hatch). The swimming abilities were estimated through the calculation of their critical swimming speed (Ucrit), their relative Ucrit and their Reynolds number (Re). Two different patterns were observed between D. dentex and S. umbra, showing a different effect of ontogeny on the performance of both species. The relative Ucrit of S. umbra decreased linearly through ontogeny, whereas the relative Ucrit and Ucrit of D. dentex increased linearly through the range of sizes tested. The ontogenetic change in Ucrit of S. umbra occurred in two stages: a first stage of sharp improvement and a second stage of a slow decrease in performance. Both stages were separated by a breakpoint that coincided with the appearance of a refusal to swim behaviour that occurred shortly after the end of metamorphosis and can potentially be associated with the establishment of this species sedentary behaviour. The swimming performance of both species showed ontogenetic differences. Sciaena umbra had the highest relative performance when its body sizes were the smallest, whereas D. dentex showed the highest relative performance when its body sizes were the largest. These results will be linked to future research on both of these species concerning their escape, exploratory and predatory behaviours, and for restocking purposes to draw a more realistic overview of hatchery-reared juvenile performance. Knowledge of both species' behavioural and swimming performance through ontogeny is important to consider when using hatchery-reared fish juveniles for restocking, as size-at-release can have a large impact on fish survival and thus on restocking success.}, } @article {pmid35750772, year = {2022}, author = {Zhang, S and Ahmad, F and Khan, A and Ali, N and Badran, M}, title = {Performance improvement and thermodynamic assessment of microchannel heat sink with different types of ribs and cones.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {10802}, pmid = {35750772}, issn = {2045-2322}, abstract = {The present study aims to investigate the performance of microchannel heat sink via numerical simulations, based on the first and second law of thermodynamics. The heat transfer and flow characteristics of rectangular microchannel heat sinks have been improved by adding six different types of surface enhancers. The cross-sections include rectangular, triangular, and hexagonal-shaped ribs and cones. The cones have been created from the same cross-sections of ribs by drafting them at an angle of 45° orthogonal to the base, which is expected to decrease the pressure drop, dramatically. The performance of ribs and cones has been evaluated using different parameters such as friction factor, wall shear stress, entropy generation rate, augmentation entropy generation number, thermal resistance, and transport efficiency of thermal energy. The results of the present study revealed that the novel effect of coning at an angle of 45° reduces frictional losses (Maximum pressure drop reduced is 85%), however; a compromise on thermal behavior has been shown (Maximum Nusselt number reduced is 25%). Similarly, the application of coning has caused a significant reduction in wall shear stress and friction factor which can lead to reducing the pumping power requirements. Moreover, triangular ribs have more ability to transfer thermal energy than rectangular and hexagonal ribs. Furthermore, it has been examined in the present study that the trend of total entropy generation rate for triangular ribs decreases up to Re = 400 and then increases onwards which means that thermal losses are more significant than frictional losses at lower Reynolds number. However, frictional losses dominate over thermal losses at higher Reynolds numbers, where vortex generation takes place, especially in triangular ribs.}, } @article {pmid35749192, year = {2022}, author = {Buaria, D and Sreenivasan, KR}, title = {Scaling of Acceleration Statistics in High Reynolds Number Turbulence.}, journal = {Physical review letters}, volume = {128}, number = {23}, pages = {234502}, doi = {10.1103/PhysRevLett.128.234502}, pmid = {35749192}, issn = {1079-7114}, abstract = {The scaling of acceleration statistics in turbulence is examined by combining data from the literature with new data from well-resolved direct numerical simulations of isotropic turbulence, significantly extending the Reynolds number range. The acceleration variance at higher Reynolds numbers departs from previous predictions based on multifractal models, which characterize Lagrangian intermittency as an extension of Eulerian intermittency. The disagreement is even more prominent for higher-order moments of the acceleration. Instead, starting from a known exact relation, we relate the scaling of acceleration variance to that of Eulerian fourth-order velocity gradient and velocity increment statistics. This prediction is in excellent agreement with the variance data. Our Letter highlights the need for models that consider Lagrangian intermittency independent of the Eulerian counterpart.}, } @article {pmid35745944, year = {2022}, author = {Chen, D and Lin, J}, title = {Steady State of Motion of Two Particles in Poiseuille Flow of Power-Law Fluid.}, journal = {Polymers}, volume = {14}, number = {12}, pages = {}, pmid = {35745944}, issn = {2073-4360}, support = {12132015//National Natural Science Foundation of China/ ; }, abstract = {The steady state of motion of two particles in Poiseuille flow of power-law fluid is numerically studied using the lattice Boltzmann method in the range of Reynolds number 20 ≤ Re ≤ 60, diameter ratio of two particles 0.125 ≤ β ≤ 2.4, and power-law index of the fluid 0.4 ≤ n ≤ 1.2. Some results are validated by comparing with other available results. The effects of Re, β, and n on the steady state of motion of two particles are discussed. The results show that, for two particles of the same diameter, the particle spacing l in the steady state is independent of n. In shear-thinning fluid, l increases rapidly at first and then slowly, finally approaching a constant for different Re. In shear-thickening fluid, although l tends to be stable in the end, the values of l after stabilization are different. For two particles of different sizes, l does not always reach a stable state, and whether it reaches a stable state depends on n. When the small particle is downstream, l increases rapidly at first and then slowly in shear-thickening fluid, but increases rapidly at first and then decreases slowly, finally approaching a constant in a shear-thinning fluid. In shear-thinning fluid, the larger n is, the smaller l is. In shear-thickening fluid, β has no effect on l in steady-state. When the large particle is downstream, l increases rapidly at first and then slowly in shear-thinning fluid but increases rapidly at first and then decreases in a shear-thickening fluid. The effect of n on l in the steady state is obvious. In shear-thinning fluid, l increases rapidly at first and then slowly, the larger Re is, the smaller l is. In shear- thickening fluid, l will reach a stable state.}, } @article {pmid35745906, year = {2022}, author = {Bui, CM and Ho, AT and Nguyen, XB}, title = {Flow Behaviors of Polymer Solution in a Lid-Driven Cavity.}, journal = {Polymers}, volume = {14}, number = {12}, pages = {}, pmid = {35745906}, issn = {2073-4360}, support = {T2021-06-03//University of Technology and Education - The University of Danang/ ; }, abstract = {In this work, a numerical study of polymer flow behaviors in a lid-driven cavity, which is inspired by the coating process, at a broad range of Oldroyd numbers (0≤Od≤50), is carried out. The Reynolds number is height-based and kept at Re=0.001. The fluid investigated is of Carbopol gel possessing yield stress and shear-thinning properties. To express rheological characteristics, the Herschel-Bulkley model cooperated with Papanastasiou's regularization scheme is utilized. Results show that the polymer flow characteristics, i.e., velocity, viscosity, and vortex distributions, are considerably influenced by viscoplastic behaviors. Additionally, there exist solid-like regions which can be of either moving rigid or static dead types in the flow patterns; they become greater and tend to merge together to construct larger ones when Od increases. Furthermore, various polymer flow aspects in different cavity configurations are discussed and analyzed; the cavity width/aspect ratio and skewed angle are found to have significant impacts on the vortex structures and the formation of solid-like regions. Moreover, results for the critical aspect ratio at which the static dead zone is broken into two parts and the characteristic height of this zone are also reported in detail.}, } @article {pmid35744569, year = {2022}, author = {Saghir, MZ and Rahman, MM}, title = {Thermo-Hydraulic Performance of Pin-Fins in Wavy and Straight Configurations.}, journal = {Micromachines}, volume = {13}, number = {6}, pages = {}, pmid = {35744569}, issn = {2072-666X}, abstract = {Pin-fins configurations have been investigated recently for different engineering applications and, in particular, for a cooling turbine. In the present study, we investigated the performance of three different pin-fins configurations: pin-fins forming a wavy mini-channel, pin-fins forming a straight mini-channel, and a mini-channel without pin-fins considering water as the working fluid. The full Navier-Stokes equations and the energy equation are solved numerically using the finite element technique. Different flow rates are studied, represented by the Reynolds number in the laminar flow regime. The thermo-hydraulic performance of the three configurations is determined by examining the Nusselt number, the pressure drop, and the performance evaluation criterion. Results revealed that pin-fins forming a wavy mini-channel exhibited the highest Nusselt number, the lowest pressure drop, and the highest performance evaluation criterion. This finding is valid for any Reynolds number under investigation.}, } @article {pmid35744548, year = {2022}, author = {Tayeb, NT and Hossain, S and Khan, AH and Mostefa, T and Kim, KY}, title = {Evaluation of Hydrodynamic and Thermal Behaviour of Non-Newtonian-Nanofluid Mixing in a Chaotic Micromixer.}, journal = {Micromachines}, volume = {13}, number = {6}, pages = {}, pmid = {35744548}, issn = {2072-666X}, abstract = {Three-dimensional numerical investigations of a novel passive micromixer were carried out to analyze the hydrodynamic and thermal behaviors of Nano-Non-Newtonian fluids. Mass and heat transfer characteristics of two heated fluids have been investigated to understand the quantitative and qualitative fluid faction distributions with temperature homogenization. The effect of fluid behavior and different Al2O3 nanoparticles concentrations on the pressure drop and thermal mixing performances were studied for different Reynolds number (from 0.1 to 25). The performance improvement simulation was conducted in intervals of various Nanoparticles concentrations (φ = 0 to 5%) with Power-law index (n) using CFD. The proposed micromixer displayed a mixing energy cost of 50-60 comparable to that achieved for a recent micromixer (2021y) in terms of fluid homogenization. The analysis exhibited that for high nanofluid concentrations, having a strong chaotic flow enhances significantly the hydrodynamic and thermal performances for all Reynolds numbers. The visualization of vortex core region of mass fraction and path lines presents that the proposed design exhibits a rapid thermal mixing rate that tends to 0.99%, and a mass fraction mixing rate of more than 0.93% with very low pressure losses, thus the proposed micromixer can be utilized to enhance homogenization in different Nano-Non-Newtonian mechanism with minimum energy.}, } @article {pmid35739213, year = {2022}, author = {Abd-Alla, AM and Abo-Dahab, SM and Thabet, EN and Abdelhafez, MA}, title = {Peristaltic pump with heat and mass transfer of a fractional second grade fluid through porous medium inside a tube.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {10608}, pmid = {35739213}, issn = {2045-2322}, mesh = {Friction ; *Hot Temperature ; Magnetic Fields ; *Peristalsis ; Porosity ; }, abstract = {In magnetic resonance imaging (MRI), this MRI is used for the diagnosis of the brain. The dynamic of these particles occurs under the action of the peristaltic waves generated on the flexible walls of the brain. Studying such fluid flow of a Fractional Second-Grade under this action is therefore useful in treating tissues of cancer. This paper deals with a theoretical investigation of the interaction of heat and mass transfer in the peristaltic flow of a magnetic field fractional second-grade fluid through a tube, under the assumption of low Reynolds number and long-wavelength. The analytical solution to a problem is obtained by using Caputo's definition. The effect of different physical parameters, the material constant, magnetic field, and fractional parameter on the temperature, concentration, axial velocity, pressure gradient, pressure rise, friction forces, and coefficient of heat and mass transfer are discussed with particular emphasis. The computed results are presented in graphical form. It is because the nature of heat and mass transfer coefficient is oscillatory which is following the physical expectation due to the oscillatory nature of the tube wall. It is perceived that with an increase in Hartmann number, the velocity decreases. A suitable comparison has been made with the prior results in the literature as a limiting case of the considered problem.}, } @article {pmid35736684, year = {2022}, author = {Zubairova, US and Kravtsova, AY and Romashchenko, AV and Pushkareva, AA and Doroshkov, AV}, title = {Particle-Based Imaging Tools Revealing Water Flows in Maize Nodal Vascular Plexus.}, journal = {Plants (Basel, Switzerland)}, volume = {11}, number = {12}, pages = {}, pmid = {35736684}, issn = {2223-7747}, support = {19-74-10037//Russian Science Foundation/ ; 19-79-10217//Russian Science Foundation/ ; }, abstract = {In plants, water flows are the major driving force behind growth and play a crucial role in the life cycle. To study hydrodynamics, methods based on tracking small particles inside water flows attend a special place. Thanks to these tools, it is possible to obtain information about the dynamics of the spatial distribution of the flux characteristics. In this paper, using contrast-enhanced magnetic resonance imaging (MRI), we show that gadolinium chelate, used as an MRI contrast agent, marks the structural characteristics of the xylem bundles of maize stem nodes and internodes. Supplementing MRI data, the high-precision visualization of xylem vessels by laser scanning microscopy was used to reveal the structural and dimensional characteristics of the stem vascular system. In addition, we propose the concept of using prototype "Y-type xylem vascular connection" as a model of the elementary connection of vessels within the vascular system. A Reynolds number could match the microchannel model with the real xylem vessels.}, } @article {pmid35699409, year = {2022}, author = {Martin, AR and Finlay, WH}, title = {Empirical Deposition Correlations.}, journal = {Journal of aerosol medicine and pulmonary drug delivery}, volume = {35}, number = {3}, pages = {109-120}, doi = {10.1089/jamp.2022.29062.arm}, pmid = {35699409}, issn = {1941-2703}, mesh = {Administration, Inhalation ; Aerosols ; *Lung/diagnostic imaging ; Particle Size ; *Pharynx ; }, abstract = {Traditionally, empirical correlations for predicting respiratory tract deposition of inhaled aerosols have been developed using limited available in vivo data. More recently, advances in medical image segmentation and additive manufacturing processes have allowed researchers to conduct extensive in vitro deposition experiments in realistic replicas of the upper and central branching airways. This work has led to a collection of empirical equations for predicting regional aerosol deposition, especially in the upper, nasal and oral airways. The present section reviews empirical correlations based on both in vivo and in vitro data, which may be used to predict total and regional deposition. Equations are presented for predicting total respiratory deposition fraction, mouth-throat fraction, nasal, and nose-throat fractions for a large variety of aerosol sizes, subject age groups, and breathing maneuvers. Use of these correlations to estimate total lung deposition is also described.}, } @article {pmid35683052, year = {2022}, author = {George, GR and Bockelmann, M and Schmalhorst, L and Beton, D and Gerstle, A and Lindermeir, A and Wehinger, GD}, title = {Influence of Foam Morphology on Flow and Heat Transport in a Random Packed Bed with Metallic Foam Pellets-An Investigation Using CFD.}, journal = {Materials (Basel, Switzerland)}, volume = {15}, number = {11}, pages = {}, pmid = {35683052}, issn = {1996-1944}, support = {ZF 4640501VS8//Federal Ministry for Economic Affairs and Energy/ ; }, abstract = {Open-cell metallic foams used as catalyst supports exhibit excellent transport properties. In this work, a unique application of metallic foam, as pelletized catalyst in a packed bed reactor, is examined. By using a wall-segment Computational Fluid Dynamics (CFD) setup, parametric analyses are carried out to investigate the influence of foam morphologies (cell size ϕ=0.45−3 mm and porosity ε=0.55−0.95) and intrinsic conductivity on flow and heat transport characteristics in a slender packed bed (N=D/dp=6.78) made of cylindrical metallic foam pellets. The transport processes have been modeled using an extended version of conventional particle-resolved CFD, i.e., flow and energy in inter-particle spaces are fully resolved, whereas the porous-media model is used for the effective transport processes inside highly-porous foam pellets. Simulation inputs include the processing parameters relevant to Steam Methane Reforming (SMR), analyzed for low (Rep~100) and high (Rep~5000) flow regimes. The effect of foam morphologies on packed beds has shown that the desired requirements contradict each other, i.e., an increase in cell size and porosity favors the reduction in pressure drop, but, it reduces the heat transfer efficiency. A design study is also conducted to find the optimum foam morphology of a cylindrical foam pellet at a higher Rep~5000, which yields ϕ = 0.45, ε = 0.8. Suitable correlations to predict the friction factor and the overall heat transfer coefficient in a foam-packed bed have been presented, which consider the effect of different foam morphologies over a range of particle Reynolds number, 100≤Rep≤5000.}, } @article {pmid35676272, year = {2022}, author = {Castro, JM and Feisel, Y}, title = {Eruption of ultralow-viscosity basanite magma at Cumbre Vieja, La Palma, Canary Islands.}, journal = {Nature communications}, volume = {13}, number = {1}, pages = {3174}, pmid = {35676272}, issn = {2041-1723}, abstract = {The viscosity of magma exerts control on all aspects of its migration through the crust to eruption. This was particularly true for the 2021 eruption of Cumbre Vieja (La Palma), which produced exceptionally fast and fluid lava at high discharge rates. We have performed concentric cylinder experiments to determine the effective viscosities of the Cumbre Vieja magma, while accounting for its chemistry, crystallinity, and temperature. Here we show that this event produced a nepheline-normative basanite with the lowest viscosity of historical basaltic eruptions, exhibiting values of less than 10 to about 160 Pa s within eruption temperatures of ~1200 to ~1150 °C. The magma's low viscosity was responsible for many eruptive phenomena that lead to particularly impactful events, including high-Reynolds number turbulent flow and supercritical states. Increases in viscosity due to crystallization-induced melt differentiation were subdued in this eruption, due in part to subtle degrees of silica enrichment in alkaline magma.}, } @article {pmid35662323, year = {2022}, author = {Ruszczyk, M and Webster, DR and Yen, J}, title = {Trends in Stroke Kinematics, Reynolds Number, and Swimming Mode in Shrimp-Like Organisms.}, journal = {Integrative and comparative biology}, volume = {}, number = {}, pages = {}, doi = {10.1093/icb/icac067}, pmid = {35662323}, issn = {1557-7023}, abstract = {Metachronal propulsion is commonly seen in organisms with the caridoid facies body plan, i.e. shrimp-like organisms, as they beat their pleopods in an adlocomotory sequence. These organisms exist across length scales ranging several orders of Reynolds number magnitude, from 10 to 104, during locomotion. Further, by altering their stroke kinematics, these organisms achieve three distinct swimming modes. To better understand the relationship between Reynolds number, stroke kinematics, and resulting swimming mode, Euphausia pacifica stroke kinematics were quantified using high-speed digital recordings and compared to the results for the larger E. superba. Euphausia pacifica consistently operate with a greater beat frequency and smaller stroke amplitude than E. superba for each swimming mode, suggesting that length scale may affect the kinematics needed to achieve similar swimming modes. To expand on this observation, these euphausiid data are used in combination with previously-published stroke kinematics from mysids and stomatopods to identify broad trends across swimming mode and length scale in metachrony. Principal component analysis (PCA) reveals trends in stroke kinematics and Reynolds number as well as the variation among taxonomic order. Overall, larger beat frequencies, stroke amplitudes, between-cycle phase lags, and Reynolds numbers are more representative of the fast forward swimming mode compared to the slower hovering mode. Additionally, each species has a unique combination of kinematics that result in metachrony, indicating that there are other factors, perhaps morphological, which affect the overall metachronal characteristics of an organism. Finally, uniform phase lag, in which the timing between power strokes of all pleopods is equal, in 5-paddle systems is achieved at different Reynolds numbers for different swimming modes, highlighting the importance of taking into consideration stroke kinematics, length scale, and the resulting swimming mode.}, } @article {pmid35642428, year = {2022}, author = {Broadley, P and Nabawy, MRA and Quinn, MK and Crowther, WJ}, title = {Dynamic experimental rigs for investigation of insect wing aerodynamics.}, journal = {Journal of the Royal Society, Interface}, volume = {19}, number = {191}, pages = {20210909}, pmid = {35642428}, issn = {1742-5662}, mesh = {Animals ; Biomechanical Phenomena ; *Flight, Animal ; Insecta ; *Models, Biological ; Wings, Animal ; }, abstract = {This paper provides a systematic and critical review of dynamic experimental rigs used for insect wing aerodynamics research. The goal is to facilitate meaningful comparison of data from existing rigs and provide insights for designers of new rigs. The scope extends from simple one degree of freedom rotary rigs to multi degrees of freedom rigs allowing various rotation and translation motions. Experimental methods are characterized using a consistent set of parameters that allows objective comparison of different approaches. A comprehensive catalogue is presented for the tested flow conditions (assessed through Reynolds number, Rossby number and advance ratio), wing morphologies (assessed through aspect ratio, planform shape and thickness to mean chord ratio) and kinematics (assessed through motion degrees of freedom). Links are made between the type of aerodynamic characteristics being studied and the type of experimental set-up used. Rig mechanical design considerations are assessed, and the aerodynamic measurements obtained from these rigs are discussed.}, } @article {pmid35637889, year = {2022}, author = {Semenov, AP and Mendgaziev, RI and Stoporev, AS and Istomin, VA and Sergeeva, DV and Tulegenov, TB and Vinokurov, VA}, title = {Dataset for the dimethyl sulfoxide as a novel thermodynamic inhibitor of carbon dioxide hydrate formation.}, journal = {Data in brief}, volume = {42}, number = {}, pages = {108289}, pmid = {35637889}, issn = {2352-3409}, abstract = {The temperatures and pressures of the three-phase equilibrium V-Lw-H (gas - aqueous solution - gas hydrate) were measured in the CO2 - H2O - dimethyl sulfoxide (DMSO) system at concentrations of organic solute in the aqueous phase up to 50 mass%. Measurements of CO2 hydrate equilibrium conditions were carried out using a constant volume autoclave by continuous heating at a rate of 0.1 K/h with simultaneous stirring of fluids by a four-blade agitator at 600 rpm. The equilibrium temperature and pressure of CO2 hydrate were determined for the endpoint of the hydrate dissociation in each experiment. The CO2 gas fugacity was calculated by the equation of state for carbon dioxide for the measured points. The flow regime in the autoclave during the operation of the stirring system was characterized by calculating the Reynolds number using literature data on the viscosity and density of water and DMSO aqueous solutions. We employed regression analysis to approximate the dependences of equilibrium pressure (CO2 gas fugacity) on temperature by two- and three-parameter equations. For each measured point, the value of CO2 hydrate equilibrium temperature suppression ΔTh was computed. The dependences of this quantity on CO2 gas fugacity are considered for all DMSO concentrations. The coefficients of empirical correlation describing ΔTh as a function of the DMSO mass fraction in solution and the equilibrium gas pressure are determined. This article is a co-submission with a paper [1].}, } @article {pmid35635664, year = {2022}, author = {Eldesoukey, A and Hassan, H}, title = {Study of the performance of thermoelectric generator for waste heat recovery from chimney: impact of nanofluid-microchannel cooling system.}, journal = {Environmental science and pollution research international}, volume = {29}, number = {49}, pages = {74242-74263}, pmid = {35635664}, issn = {1614-7499}, abstract = {A huge number of chimneys all over the world utilized in many industrial applications and applications like restaurants, homes, etc. contribute badly on the global warming and climate change due to their waste heat. So, in this paper, the performance of thermoelectric generator (TEG) cooled by microchannel heat spreader having nanofluid and used for waste heat recovery from vertical chimney is investigated. Using heat spreader with microchannel cooling system increases the output TEG power compared to natural convection cooling system. In this paper, the impact of microchannel sizes, using nanofluid and heat spreader with different sizes on the TEG performance and cooling, is considered. Three-dimensional mathematical models including TEG, microchannel, nanofluid, and heat spreader are presented and solved by Ansys Fluent software utilizing user-defined memory, user-defined function, and user-defined scalar. All TEG effects (Joule, Seebeck, and Thomson) are considered in TEG model. Results indicate that TEG power rises with increasing the heat spreader and microchannel sizes together. Increasing microchannel and heat spreader sizes four times of TEG size raises the TEG output power by 10%. This also achieves the maximum cooling system efficiency of 88.9% and the maximum net output power. Microchannel heat spreader cooling system raises the system (TEG power-pumping power) net power by 125.2% compared to the normal channel and decreases the required cooling fluid flow rate. Utilizing copper-water and Al2O3-water nanofluids rises maximally the TEG output power by 14% and 4%, respectively; however, it increases the pumping power. Moreover, using nanofluids increases the net output power at low Reynolds number and decreases it at higher Reynolds number.}, } @article {pmid35630837, year = {2022}, author = {Souayeh, B and Ramesh, K and Hdhiri, N and Yasin, E and Alam, MW and Alfares, K and Yasin, A}, title = {Heat Transfer Attributes of Gold-Silver-Blood Hybrid Nanomaterial Flow in an EMHD Peristaltic Channel with Activation Energy.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {10}, pages = {}, pmid = {35630837}, issn = {2079-4991}, support = {AN00052//Deanship of Scientific Research at King Faisal University/ ; }, abstract = {The heat enhancement in hybrid nanofluid flow through the peristaltic mechanism has received great attention due to its occurrence in many engineering and biomedical systems, such as flow through canals, the cavity flow model and biomedicine. Therefore, the aim of the current study was to discuss the hybrid nanofluid flow in a symmetric peristaltic channel with diverse effects, such as electromagnetohydrodynamics (EMHD), activation energy, gyrotactic microorganisms and solar radiation. The equations governing this motion were simplified under the approximations of a low Reynolds number (LRN), a long wavelength (LWL) and Debye-Hückel linearization (DHL). The numerical solutions for the non-dimensional system of equations were tackled using the computational software Mathematica. The influences of diverse physical parameters on the flow and thermal characteristics were computed through pictorial interpretations. It was concluded from the results that the thermophoresis parameter and Grashof number increased the hybrid nanofluid velocity near the right wall. The nanoparticle temperature decreased with the radiation parameter and Schmidt number. The activation energy and radiation enhanced the nanoparticle volume fraction, and motile microorganisms decreased with an increase in the Peclet number and Schmidt number. The applications of the current investigation include chyme flow in the gastrointestinal tract, the control of blood flow during surgery by altering the magnetic field and novel drug delivery systems in pharmacological engineering.}, } @article {pmid35630375, year = {2022}, author = {Soares, A and Gomes, LC and Monteiro, GA and Mergulhão, FJ}, title = {Hydrodynamic Effects on Biofilm Development and Recombinant Protein Expression.}, journal = {Microorganisms}, volume = {10}, number = {5}, pages = {}, pmid = {35630375}, issn = {2076-2607}, support = {LA/P/0045/2020 (ALiCE), UIDB/00511/2020 and UIDP/00511/2020 (LEPABE)//FCT/MCTES (PIDDAC)/ ; PTDC/BII-BIO/29589/2017 - POCI-01-0145-FEDER-029589//FEDER funds through COMPETE2020 - Programa Operacional Competitividade e Internacionalização (POCI) and by national funds (PIDDAC) through FCT/MCTES/ ; SFRH/BD/141614/2018; CEECIND/01700/2017//FCT/ ; }, abstract = {Hydrodynamics play an important role in the rate of cell attachment and nutrient and oxygen transfer, which can affect biofilm development and the level of recombinant protein production. In the present study, the effects of different flow conditions on the development of Escherichia coli biofilms and the expression of a model recombinant protein (enhanced green fluorescent protein, eGFP) were examined. Planktonic and biofilm cells were grown at two different flow rates in a recirculating flow cell system for 7 days: 255 and 128 L h[-1] (corresponding to a Reynolds number of 4600 and 2300, respectively). The fluorometric analysis showed that the specific eGFP production was higher in biofilms than in planktonic cells under both hydrodynamic conditions (3-fold higher for 255 L h[-1] and 2-fold higher for 128 L h[-1]). In the biofilm cells, the percentage of eGFP-expressing cells was on average 52% higher at a flow rate of 255 L h[-1]. Furthermore, a higher plasmid copy number (PCN) was obtained for the highest flow rate for both planktonic (244 PCN/cell versus 118 PCN/cell) and biofilm cells (43 PCN/cell versus 29 PCN/cell). The results suggested that higher flow velocities promoted eGFP expression in E. coli biofilms.}, } @article {pmid35626546, year = {2022}, author = {Alenezi, A and Almutairi, A and Alhajeri, H and Almekmesh, SF and Alzuwayer, BB}, title = {Impact of Surface Roughness on Flow Physics and Entropy Generation in Jet Impingement Applications.}, journal = {Entropy (Basel, Switzerland)}, volume = {24}, number = {5}, pages = {}, pmid = {35626546}, issn = {1099-4300}, abstract = {In this paper, a numerical investigation was performed of an air jet incident that normally occurs on a horizontal heated plane. Analysis of flow physics and entropy generation due to heat and friction is included using a simple easy-to-manufacture, surface roughening element: a circular rib concentric with the air jet. This study shows how varying the locations and dimensions of the rib can deliver a favorable trade-off between entropy generation and flow parameters, such as vortex generation and heat transfer. The performance of the roughness element was tested at three different radii; R/D = 1, 1.5 and 2, where D was the jet hydraulic diameter and R was the radial distance from the geometric center. At each location, the normalized rib height (e/D) was increased from 0.019 to 0.074 based on an increment of (e/D) = 0.019. The jet-to-target distance was H/D = 6 and the jet Reynolds number (Re) ranged from 10,000 to 50,000 Re, which was obtained from the jet hydraulic diameter (D), and the jet exit velocity (U). All results are presented in the form of entropy generation due to friction and heat exchange, as well as the total entropy generated. A detailed comparison of flow physics is presented for all ribs and compared with the baseline case of a smooth surface. The results show that at higher Reynolds numbers, adding a rib of a suitable height reduced the total entropy (St) by 31% compared to the no rib case. In addition, with ribs of heights 0.019, 0.037 and 0.054, respectively, the entropy generated by friction (Sf) was greater than that due to heat exchange (Sh) by about 42%, 26% and 4%, respectively. The rib of height e/D = 0.074 produced the minimum St at R/D = 1. As for varying R/D, varying rib location and Re values had a noticeable impact on Sh, Sf and (St). Placing the rib at R/D = 1 gave the highest total entropy generation (St) followed by R/D = 1.5 for all Re. Finally, the Bejan number increased as both rib height and rib location increased.}, } @article {pmid35626500, year = {2022}, author = {Dressler, L and Nicolai, H and Agrebi, S and Ries, F and Sadiki, A}, title = {Computation of Entropy Production in Stratified Flames Based on Chemistry Tabulation and an Eulerian Transported Probability Density Function Approach.}, journal = {Entropy (Basel, Switzerland)}, volume = {24}, number = {5}, pages = {}, pmid = {35626500}, issn = {1099-4300}, support = {SA 836/15-1//Deutsche Forschungsgemeinschaft/ ; }, abstract = {This contribution presents a straightforward strategy to investigate the entropy production in stratified premixed flames. The modeling approach is grounded on a chemistry tabulation strategy, large eddy simulation, and the Eulerian stochastic field method. This enables a combination of a detailed representation of the chemistry with an advanced model for the turbulence chemistry interaction, which is crucial to compute the various sources of exergy losses in combustion systems. First, using detailed reaction kinetic reference simulations in a simplified laminar stratified premixed flame, it is demonstrated that the tabulated chemistry is a suitable approach to compute the various sources of irreversibilities. Thereafter, the effects of the operating conditions on the entropy production are investigated. For this purpose, two operating conditions of the Darmstadt stratified burner with varying levels of shear have been considered. The investigations reveal that the contribution to the entropy production through mixing emerging from the chemical reaction is much larger than the one caused by the stratification. Moreover, it is shown that a stronger shear, realized through a larger Reynolds number, yields higher entropy production through heat, mixing and viscous dissipation and reduces the share by chemical reaction to the total entropy generated.}, } @article {pmid35621794, year = {2022}, author = {Li, H and Nabawy, MRA}, title = {Wing Planform Effect on the Aerodynamics of Insect Wings.}, journal = {Insects}, volume = {13}, number = {5}, pages = {}, pmid = {35621794}, issn = {2075-4450}, support = {RPG-2019-366//Leverhulme Trust/ ; }, abstract = {This study investigates the effect of wing planform shape on the aerodynamic performance of insect wings by numerically solving the incompressible Navier-Stokes equations. We define the wing planforms using a beta-function distribution and employ kinematics representative of normal hovering flight. In particular, we use three primary parameters to describe the planform geometry: aspect ratio, radial centroid location, and wing root offset. The force coefficients, flow structures, and aerodynamic efficiency for different wing planforms at a Reynolds number of 100 are evaluated. It is found that the wing with the lowest aspect ratio of 1.5 results in the highest peaks of lift and drag coefficients during stroke reversals, whereas the higher aspect ratio wings produce higher lift and drag coefficients during mid half-stroke translation. For the wings considered, the leading-edge vortex detachment is found to be approximately at a location that is 3.5-5 mean chord lengths from the wing center of rotation for all aspect ratios and root offsets investigated. Consequently, the detachment area increases with the increase of aspect ratio and root offset, resulting in reduced aerodynamic coefficients. The radial centroid location is found to influence the local flow evolution time, and this results in earlier formation/detachment of the leading-edge vortex for wings with a smaller radial centroid location. Overall, the best performance, when considering both average lift coefficient and efficiency, is found at the intermediate aspect ratios of 4.5-6; increasing the centroid location mainly increases efficiency; and increasing the root offset leads to a decreased average lift coefficient whilst leading to relatively small variations in aerodynamic efficiency for most aspect ratios.}, } @article {pmid35617810, year = {2022}, author = {Huang, F and Noël, R and Berg, P and Hosseini, SA}, title = {Simulation of the FDA nozzle benchmark: A lattice Boltzmann study.}, journal = {Computer methods and programs in biomedicine}, volume = {221}, number = {}, pages = {106863}, doi = {10.1016/j.cmpb.2022.106863}, pmid = {35617810}, issn = {1872-7565}, mesh = {*Benchmarking ; Computer Simulation ; *Hemodynamics ; Rheology ; }, abstract = {BACKGROUND AND OBJECTIVE: Contrary to flows in small intracranial vessels, many blood flow configurations such as those found in aortic vessels and aneurysms involve larger Reynolds numbers and, therefore, transitional or turbulent conditions. Dealing with such systems require both robust and efficient numerical methods.

METHODS: We assess here the performance of a lattice Boltzmann solver with full Hermite expansion of the equilibrium and central Hermite moments collision operator at higher Reynolds numbers, especially for under-resolved simulations. To that end the food and drug administration's benchmark nozzle is considered at three different Reynolds numbers covering all regimes: (1) laminar at a Reynolds number of 500, (2) transitional at a Reynolds number of 3500, and (3) low-level turbulence at a Reynolds number of 6500.

RESULTS: The lattice Boltzmann results are compared with previously published inter-laboratory experimental data obtained by particle image velocimetry. Our results show good agreement with the experimental measurements throughout the nozzle, demonstrating the good performance of the solver even in under-resolved simulations.

CONCLUSION: In this manner, fast but sufficiently accurate numerical predictions can be achieved for flow configurations of practical interest regarding medical applications.}, } @article {pmid35598483, year = {2022}, author = {Sharma, S and Jain, S and Saha, A and Basu, S}, title = {Evaporation dynamics of a surrogate respiratory droplet in a vortical environment.}, journal = {Journal of colloid and interface science}, volume = {623}, number = {}, pages = {541-551}, doi = {10.1016/j.jcis.2022.05.061}, pmid = {35598483}, issn = {1095-7103}, mesh = {Crystallization ; Gases ; *Respiratory Aerosols and Droplets ; *Sodium Chloride/chemistry ; Water/chemistry ; }, abstract = {HYPOTHESIS: Vortex droplet interaction is crucial for understanding the route of disease transmission through expiratory jet where several such embedded droplets continuously interact with vortical structures of different strengths and sizes.

EXPERIMENTS: A train of vortex rings with different vortex strength, quantified with vortex Reynolds number (Re[']=0,53,221,297) are made to interact with an isolated levitated droplet, and the evolution dynamics is captured using shadowgraphy, particle image velocimetry (PIV), and backlight imaging technique. NaCl-DI water solution of 0, 1, 10 and 20 wt% concentrations are used as test fluids for the droplet.

FINDINGS: The results show the dependence of evaporation characteristics on vortex strength, while the crystallization dynamics was found to be independent of it. A reduction of 12.23% and 14.6% in evaporation time was seen in case of de-ionized (DI) water and 1% wt NaCl solution respectively in presence of vortex ring train at Re[']=221. In contrast to this, a minimal reduction in evaporation time (0.6% and 0.9% for DI water and 1% wt NaCl solution, respectively) is observed when Re['] is increased from 221 to 297. The mechanisms for evaporation time reduction due to enhancement of convective heat and mass transfer from the droplet and shearing away of vapor layer by vortex ring interaction are discussed in this work.}, } @article {pmid35591423, year = {2022}, author = {Karmveer, and Kumar Gupta, N and Siddiqui, MIH and Dobrotă, D and Alam, T and Ali, MA and Orfi, J}, title = {The Effect of Roughness in Absorbing Materials on Solar Air Heater Performance.}, journal = {Materials (Basel, Switzerland)}, volume = {15}, number = {9}, pages = {}, pmid = {35591423}, issn = {1996-1944}, abstract = {Artificial roughness on the absorber of the solar air heater (SAH) is considered to be the best passive technology for performance improvement. The roughened SAHs perform better in comparison to conventional SAHs under the same operational conditions, with some penalty of higher pumping power requirements. Thermo-hydraulic performance, based on effective efficiency, is much more appropriate to design roughened SAH, as it considers both the requirement of pumping power and useful heat gain. The shape, size, and arrangement of artificial roughness are the most important factors for the performance optimization of SAHs. The parameters of artificial roughness and operating parameters, such as the Reynolds number (Re), temperature rise parameter (ΔT/I) and insolation (I) show a combined effect on the performance of SAH. In this case study, various performance parameters of SAH have been evaluated to show the effect of distinct artificial roughness, investigated previously. Therefore, thermal efficiency, thermal efficiency improvement factor (TEIF) and the effective efficiency of various roughened absorbers of SAH have been predicted. As a result, thermal and effective efficiencies strongly depend on the roughness parameter, Re and ΔT/I. Staggered, broken arc hybrid-rib roughness shows a higher value of TEIF, thermal and effective efficiencies consistently among all other distinct roughness geometries for the ascending values of ΔT/I. This roughness shows the maximum value of effective efficiency equals 74.63% at a ΔT/I = 0.01 K·m[2]/W. The unique combination of parameters p/e = 10, e/Dh = 0.043 and α = 60° are observed for best performance at a ΔT/I higher than 0.00789 K·m[2]/W.}, } @article {pmid35591154, year = {2022}, author = {Salem, S and Fraňa, K}, title = {A Wind Tunnel Study of the Flow-Induced Vibrations of a Cylindrical Piezoelectric Transducer.}, journal = {Sensors (Basel, Switzerland)}, volume = {22}, number = {9}, pages = {}, pmid = {35591154}, issn = {1424-8220}, support = {SGS-2022-5040//Technical University of Liberec - SGS/ ; CZ.02.1.01/0.0/0.0/16_019/0000843//European Union and the Czech Government/ ; }, abstract = {Piezoelectric transducers are used as a sensing device to study the fluids' motion. Moreover, they are used as a harvester of energy of Flow-Induced Vibration (FIV). The current FIV harvesters in the literature rely on piezoelectric cantilevers coupled with a bluff body that creates flow instabilities. This paper studies the use of piezoelectric cylinders as a novel transducer in the field of fluid mechanics, where the transducer makes use of its bluff geometry to create instability. The study was based on wind tunnel measurements performed on four piezoelectric cylinders of different sizes over a speed range of 1-7 m/s. The paper looks at the variation of the generated voltage across the Reynolds number. It also compares the spectra of the generated open-circuit voltage to the turbulence spectra features known from the literature.}, } @article {pmid35590864, year = {2022}, author = {Funatani, S and Tsukamoto, Y and Toriyama, K}, title = {Temperature Measurement of Hot Airflow Using Ultra-Fine Thermo-Sensitive Fluorescent Wires.}, journal = {Sensors (Basel, Switzerland)}, volume = {22}, number = {9}, pages = {}, pmid = {35590864}, issn = {1424-8220}, abstract = {In this paper, we propose a temperature measurement method that uses ultrafine fluorescent wires to reduce the wire diameter to a much lesser extent than a thermocouple. This is possible because its structure is simple and any material can be used for the wire. Hence, ultrafine wires with a Reynolds number of less than 1.0 can be selected. Ultra-fine wires less than 50 µm in diameter were set in the test volume. The wire surfaces were coated with fluorescent paint. The test volume was illuminated using an ultraviolet light-emitting diode. The paint emits very tiny, orange-colored fluorescent light with an intensity that changes with the temperature of the atmosphere. The experimental results showed that the heating/cooling layers were well visualized and the temperature field was well analyzed.}, } @article {pmid35590633, year = {2022}, author = {Wang, G and Fei, L and Luo, KH}, title = {Unified lattice Boltzmann method with improved schemes for multiphase flow simulation: Application to droplet dynamics under realistic conditions.}, journal = {Physical review. E}, volume = {105}, number = {4-2}, pages = {045314}, doi = {10.1103/PhysRevE.105.045314}, pmid = {35590633}, issn = {2470-0053}, abstract = {As a powerful mesoscale approach, the lattice Boltzmann method (LBM) has been widely used for the numerical study of complex multiphase flows. Recently, Luo et al. [Philos. Trans. R. Soc. A: Math. Phys. Eng. Sci. 379, 20200397 (2021)10.1098/rsta.2020.0397] proposed a unified lattice Boltzmann method (ULBM) to integrate the widely used lattice Boltzmann collision operators into a unified framework. In this study, we incorporate additional features into this ULBM in order to simulate multiphase flow under realistic conditions. A nonorthogonal moment set [Fei et al., Phys. Rev. E 97, 053309 (2018)10.1103/PhysRevE.97.053309] and the entropic-multi-relaxation-time (KBC) lattice Boltzmann model are used to construct the collision operator. An extended combined pseudopotential model is proposed to realize multiphase flow simulation at high-density ratio with tunable surface tension over a wide range. The numerical results indicate that the improved ULBM can significantly decrease the spurious velocities and adjust the surface tension without appreciably changing the density ratio. The ULBM is validated through reproducing various droplet dynamics experiments, such as binary droplet collision and droplet impingement on superhydrophobic surfaces. Finally, the extended ULBM is applied to complex droplet dynamics, including droplet pancake bouncing and droplet splashing. The maximum Weber number and Reynolds number in the simulation reach 800 and 7200, respectively, at a density ratio of 1000. The study demonstrates the generality and versatility of ULBM for incorporating schemes to tackle challenging multiphase problems.}, } @article {pmid35590627, year = {2022}, author = {Verma, S and Hemmati, A}, title = {Route to transition in propulsive performance of oscillating foil.}, journal = {Physical review. E}, volume = {105}, number = {4-2}, pages = {045102}, doi = {10.1103/PhysRevE.105.045102}, pmid = {35590627}, issn = {2470-0053}, abstract = {Transition in the propulsive performance and vortex synchronization of an oscillating foil in a combined heaving and pitching motion is numerically investigated at a range of reduced frequencies (0.16 ≤f^{*}≤ 0.64), phase offsets (0^{∘} ≤ϕ≤ 315^{∘}), and Reynolds number (1000≤Re≤16000). Focusing on the common case of Re=1000, the drag to thrust transition is identified on a ϕ-f^{*} phase map. Here, the range of 90^{∘} ≤ϕ≤ 225^{∘} depicted a drag-dominated regime for increasing reduced frequency. However, thrust-dominated regimes were observed for ϕ< 90^{∘} and ϕ> 225^{∘}, where increasing the reduced frequency led to an increased thrust production. The isoline-depicting drag-thrust boundary was further observed to coincide with transitions in the characteristic near-wake modes with increasing reduced frequency, which ranged from 2P+2S to 2P and reverse von Kármán modes. However, evaluation of the wake with changing phase offsets at individual reduced frequencies only depicted effects on the spatial configuration of the vortex structures, while the number of vortices shed in one oscillation period was unchanged. The existence of similar wake modes with significantly different propulsive performance clearly suggests that transitions of the wake topology may not always be a reliable tool for understanding propulsive mechanisms of fish swimming or development of underwater propulsion systems. We further assessed a possible route to drag production via investigation into the mean velocity fields at increasing phase offset and at intermediate reduced frequencies ranging from 0.24 to 0.40. This revealed bifurcation of a velocity jet behind the foil on account of the wake topology and dynamics of shed vortex structures. The changes posed by increasing ϕ on wake structure interactions further hints at potential mechanisms that limit the achievement of optimum efficiency in underwater locomotion.}, } @article {pmid35580542, year = {2022}, author = {Ge, M and Sun, C and Zhang, G and Coutier-Delgosha, O and Fan, D}, title = {Combined suppression effects on hydrodynamic cavitation performance in Venturi-type reactor for process intensification.}, journal = {Ultrasonics sonochemistry}, volume = {86}, number = {}, pages = {106035}, pmid = {35580542}, issn = {1873-2828}, abstract = {Hydrodynamic cavitation is an emerging intensification technology in water treatment or chemical processing, and Venturi-type cavitation reactors exhibit advantages for industrial-scale production. The effects of temperature on hydrodynamic cavitating flows are investigated to find the optimum reaction conditions enhancing cavitating treatment intensity. Results show that the cavitation performance, including the cavitation intensity and cavitation unsteady behavior, is influenced by (1) cavitation number σ (the pressure difference affecting the vaporization process), (2) Reynolds number Re (the inertial/viscous ratio affecting the bubble size and liquid-vapor interface area), and (3) thermodynamic parameter Σ (the thermal effect affecting the temperature drop). With increasing temperature, the cavitation length first increases and then decreases, with a cavitation intensity peak at the transition temperature of 58 °C. With the growth of cavitation extent, the cavity-shedding regimes tend to transition from the attached sheet cavity to the periodic cloud cavity, and the vapor volume fluctuating frequency decreases accordingly. A combined suppression parameter (CSP) is provided to predict that, with increasing CSP value, the cavitation intensity can be decreased. Recommendations are given that working under the low-CSP range (55-60 °C) could enhance the intensification of the cavitation process.}, } @article {pmid35567865, year = {2022}, author = {Cherkaoui, I and Bettaibi, S and Barkaoui, A and Kuznik, F}, title = {Magnetohydrodynamic blood flow study in stenotic coronary artery using lattice Boltzmann method.}, journal = {Computer methods and programs in biomedicine}, volume = {221}, number = {}, pages = {106850}, doi = {10.1016/j.cmpb.2022.106850}, pmid = {35567865}, issn = {1872-7565}, mesh = {*Atherosclerosis ; Blood Flow Velocity/physiology ; Computer Simulation ; Constriction, Pathologic ; *Coronary Vessels ; Hemodynamics/physiology ; Humans ; Hydrodynamics ; Models, Cardiovascular ; }, abstract = {BACKGROUND AND OBJECTIVE: Cardiovascular diseases such as atherosclerosis are the first engender of death in the world. The malfunctioning of cardiovascular system is attributed mainly to hemodynamics. However, blood magnetic properties are of major haemodynamic interest, with significant clinical applications. The aim of this work is to study numerically the effect of high magnetic field on blood flow in stenotic artery.

METHODS: In this paper, a double population D2Q9 lattice Boltzmann model is proposed. Velocity and magnetic field are both solved using Lattice Boltzmann method with single relaxation time. Blood is considered homogeneous and Newtonian bio-magnetic fluid. The results of the proposed model are compared and validated by recent numerical and experimental studies in the literature and show good agreement. In this study, simulations are carried out for both hydrodynamics and magneto-hydrodynamics. For the magneto-hydrodynamic case, five values of Hartmann number of 10, 30, 50, 75 and 100 at Reynolds number of 400, 600 and 800 are investigated Results: The results show that velocity and recirculation zone increase with the increase of the degree of stenosis and Reynolds number. In addition, a considerable decrease in velocity, recirculation zones and pressure drop across the stenotic artery is noticed with the increase of Hartmann number.

CONCLUSION: The suggested model is found to be effective and accurate in the treatment of magneto-hydrodynamic blood flow in stenotic artery. The found results can be used by clinicians in the treatment of certain cardiovascular disorders and in regulating blood flow movement, especially during surgical procedures.}, } @article {pmid35551230, year = {2022}, author = {Chew, SH and Hoi, SM and Tran, MV and Foo, JJ}, title = {Partially-covered fractal induced turbulence on fins thermal dissipation.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {7861}, pmid = {35551230}, issn = {2045-2322}, support = {FRGS/1/2018/TK07/MUSM/02/1//Ministry of Higher Education, Malaysia/ ; FRGS/1/2018/TK07/MUSM/02/1//Ministry of Higher Education, Malaysia/ ; MUM25929267//Monash University Malaysia/ ; }, abstract = {The impacts of partially-covered fractal grids induced turbulence on the forced convective heat transfer across plate-fin heat sink at Reynolds number ReDh = 22.0 × 10[3] were numerically and experimentally investigated. Results showed that partially covered grids rendered a higher thermal dissipation performance, with partially-covered square fractal grid (PCSFG) registering an outstanding increase of 43% in Nusselt number relative to the no grid configuration. The analyzation via an in-house developed single particle tracking velocimetry (SPTV) system displayed the findings of unique "Turbulence Annulus" formation, which provided a small degree of predictivity in the periodic annulus oscillations. Further assessments on PCSFG revealed the preferred inter-fin flow dynamics of (i) high flow velocity, (ii) strong turbulence intensity, (iii) vigorous flow fluctuations, (iv) small turbulence length scale, and (v) heightened decelerated flow events. These features stemmed from the coupling effects of multilength-scale fractal bar thicknesses in generating a veracity of eddy sizes, and a vertical segmentation producing heightened mass flow rate while inducing favourable wake-flow structures to penetrate inter-fin regions. Teeming effects of such energetic eddies within plate-fin array unveiled a powerful vortex shedding effect, with PCSFG achieving fluctuation frequency f = 18.5 Hz close to an optimal magnitude. The coaction of such traits limits the growth of fin boundary layers, providing superior thermal transfer capabilities which benefits the community in developing for higher efficiency heat transfer systems.}, } @article {pmid35547578, year = {2022}, author = {Qiao, Y and Luo, K and Fan, J}, title = {Computational Prediction of Thrombosis in Food and Drug Administration's Benchmark Nozzle.}, journal = {Frontiers in physiology}, volume = {13}, number = {}, pages = {867613}, pmid = {35547578}, issn = {1664-042X}, abstract = {Thrombosis seriously threatens human cardiovascular health and the safe operation of medical devices. The Food and Drug Administration's (FDA) benchmark nozzle model was designed to include the typical structure of medical devices. However, the thrombosis in the FDA nozzle has yet not been investigated. The objective of this study is to predict the thrombus formation process in the idealized medical device by coupling computational fluid dynamics and a macroscopic hemodynamic-based thrombus model. We developed the hemodynamic-based thrombus model by considering the effect of platelet consumption. The thrombus model was quantitatively validated by referring to the latest thrombosis experiment, which was performed in a backward-facing step with human blood flow. The same setup was applied in the FDA nozzle to simulate the thrombus formation process. The thrombus shaped like a ring was firstly observed in the FDA benchmark nozzle. Subsequently, the accuracy of the shear-stress transport turbulence model was confirmed in different turbulent flow conditions. Five scenarios with different Reynolds numbers were carried out. We found that turbulence could change the shape of centrosymmetric thrombus to axisymmetric and high Reynolds number blood flow would delay or even prevent thrombosis. Overall, the present study reports the thrombosis process in the FDA benchmark nozzle using the numerical simulation method, and the primary findings may shed light on the effect of turbulence on thrombosis.}, } @article {pmid35546646, year = {2022}, author = {Gil, A and Navarro, R and Quintero, P and Mares, A and Pérez, M and Montero, JA}, title = {CFD analysis of the HVAD's hemodynamic performance and blood damage with insight into gap clearance.}, journal = {Biomechanics and modeling in mechanobiology}, volume = {21}, number = {4}, pages = {1201-1215}, pmid = {35546646}, issn = {1617-7940}, support = {MODELVAD//Fundación para la Investigación del Hospital Universitari La Fe/ ; }, mesh = {Equipment Design ; *Heart Failure ; *Heart-Assist Devices ; Hemodynamics ; Hemolysis ; Humans ; }, abstract = {Mechanical circulatory support using ventricular assist devices has become commonplace in the treatment of patients suffering from advanced stages of heart failure. While blood damage generated by these devices has been evaluated in depth, their hemodynamic performance has been investigated much less. This work presents the analysis of the complete operating map of a left ventricular assist device, in terms of pressure head, power and efficiency. Further investigation into its hemocompatibility is included as well. To achieve these objectives, computational fluid dynamics simulations of a centrifugal blood pump with a wide-blade impeller were performed. Several conditions were considered by varying the rotational speed and volumetric flow rate. Regarding the device's hemocompatibility, blood damage was evaluated by means of the hemolysis index. By relating the hemocompatibility of the device to its hemodynamic performance, the results have demonstrated that the highest hemolysis occurs at low flow rates, corresponding to operating conditions of low efficiency. Both performance and hemocompatibility are affected by the gap clearance. An innovative investigation into the influence of this design parameter has yielded decreased efficiencies and increased hemolysis as the gap clearance is reduced. As a further novelty, pump operating maps were non-dimensionalized to highlight the influence of Reynolds number, which allows their application to any working condition. The pump's operating range places it in the transitional regime between laminar and turbulent, leading to enhanced efficiency for the highest Reynolds number.}, } @article {pmid35544978, year = {2022}, author = {Sander, A and Petračić, A and Zokić, I and Vrsaljko, D}, title = {Scaling up extractive deacidification of waste cooking oil.}, journal = {Journal of environmental management}, volume = {316}, number = {}, pages = {115222}, doi = {10.1016/j.jenvman.2022.115222}, pmid = {35544978}, issn = {1095-8630}, mesh = {*Biofuels/analysis ; Cooking ; *Fatty Acids, Nonesterified ; Plant Oils ; Solvents ; }, abstract = {Biodiesel produced from waste feedstocks can play a significant role in fighting climate change, improperly disposed waste and growing energy demand. Waste feedstocks such as used cooking oil have a great potential for energy production. However, they often have to be purified from free fatty acids prior to biodiesel production. Extractive deacidification with deep eutectic solvents is a promising alternative to conventional purification methods. To evaluate the process of extractive deacidification of waste cooking oil, a full set of physical, hydrodynamic and kinetic data were experimentally determined on a laboratory scale. Hydrodynamic and kinetic experiments were performed in three geometrically similar jacketed agitated vessels. Vessels were equipped with axial flow impeller (four pitched blade impeller). Physical properties (density, viscosity and surface tension) were experimentally determined. Preliminary hydrodynamic experiments involved several model systems without mass transfer. As a result, correlation between power number and Reynolds number as well as scale-up criterion was developed. Obtained dependencies were correlated with the physical properties. Mixing intensity for achieving complete dispersion was determined. Second stage of investigation involved two sets of experiments, hydrodynamic and kinetic, with interphase mass transfer (the extraction of free fatty acids from waste cooking oil with deep eutectic solvent, potassium carbonate:ethylene glycol, 1:10). Obtained results enabled understanding interphase mass transfer and prediction of mass transfer coefficient from the derived dimensionless correlations. The values of volumetric mass transfer coefficients were smaller for the dispersed phase, indicating that the prevailing mass transfer resistance was within the droplets. The working hypothesis was that the same process result should be achieved at the same dispersion rate, and that hypothesis was confirmed - at all scales extraction efficiency was 97.9 ± 0.1%.}, } @article {pmid35544559, year = {2022}, author = {Callaham, JL and Rigas, G and Loiseau, JC and Brunton, SL}, title = {An empirical mean-field model of symmetry-breaking in a turbulent wake.}, journal = {Science advances}, volume = {8}, number = {19}, pages = {eabm4786}, pmid = {35544559}, issn = {2375-2548}, abstract = {Improved turbulence modeling remains a major open problem in mathematical physics. Turbulence is notoriously challenging, in part due to its multiscale nature and the fact that large-scale coherent structures cannot be disentangled from small-scale fluctuations. This closure problem is emblematic of a greater challenge in complex systems, where coarse-graining and statistical mechanics descriptions break down. This work demonstrates an alternative data-driven modeling approach to learn nonlinear models of the coherent structures, approximating turbulent fluctuations as state-dependent stochastic forcing. We demonstrate this approach on a high-Reynolds number turbulent wake experiment, showing that our model reproduces empirical power spectra and probability distributions. The model is interpretable, providing insights into the physical mechanisms underlying the symmetry-breaking behavior in the wake. This work suggests a path toward low-dimensional models of globally unstable turbulent flows from experimental measurements, with broad implications for other multiscale systems.}, } @article {pmid35535750, year = {2022}, author = {Zhang, R and Toonder, JD and Onck, PR}, title = {Metachronal patterns by magnetically-programmable artificial cilia surfaces for low Reynolds number fluid transport and mixing.}, journal = {Soft matter}, volume = {18}, number = {20}, pages = {3902-3909}, doi = {10.1039/d1sm01680f}, pmid = {35535750}, issn = {1744-6848}, mesh = {Biological Transport ; *Cilia/metabolism ; *Magnetics ; Models, Biological ; Motion ; }, abstract = {Motile cilia can produce net fluid flows at low Reynolds number because of their asymmetric motion and metachrony of collective beating. Mimicking this with artificial cilia can find application in microfluidic devices for fluid transport and mixing. Here, we study the metachronal beating of nonidentical, magnetically-programmed artificial cilia whose individual non-reciprocal motion and collective metachronal beating pattern can be independently controlled. We use a finite element method that accounts for magnetic forces, cilia deformation and fluid flow in a fully coupled manner. Mimicking biological cilia, we study magnetic cilia subject to a full range of metachronal driving patterns, including antiplectic, symplectic, laeoplectic and diaplectic waves. We analyse the induced primary flow, secondary flow and mixing rate as a function of the phase lag between cilia and explore the underlying physical mechanism. Our results show that shielding effects between neighboring cilia lead to a primary flow that is larger for antiplectic than for symplectic metachronal waves. The secondary flow can be fully explained by the propagation direction of the metachronal wave. Finally, we show that the mixing rate can be strongly enhanced by laeoplectic and diaplectic metachrony resulting in large velocity gradients and vortex-like flow patterns.}, } @article {pmid35527637, year = {2022}, author = {Gomé, S and Tuckerman, LS and Barkley, D}, title = {Extreme events in transitional turbulence.}, journal = {Philosophical transactions. Series A, Mathematical, physical, and engineering sciences}, volume = {380}, number = {2226}, pages = {20210036}, doi = {10.1098/rsta.2021.0036}, pmid = {35527637}, issn = {1471-2962}, abstract = {Transitional localized turbulence in shear flows is known to either decay to an absorbing laminar state or to proliferate via splitting. The average passage times from one state to the other depend super-exponentially on the Reynolds number and lead to a crossing Reynolds number above which proliferation is more likely than decay. In this paper, we apply a rare-event algorithm, Adaptative Multilevel Splitting, to the deterministic Navier-Stokes equations to study transition paths and estimate large passage times in channel flow more efficiently than direct simulations. We establish a connection with extreme value distributions and show that transition between states is mediated by a regime that is self-similar with the Reynolds number. The super-exponential variation of the passage times is linked to the Reynolds number dependence of the parameters of the extreme value distribution. Finally, motivated by instantons from Large Deviation theory, we show that decay or splitting events approach a most-probable pathway. This article is part of the theme issue 'Mathematical problems in physical fluid dynamics (part 2)'.}, } @article {pmid35527633, year = {2022}, author = {Drivas, TD}, title = {Self-regularization in turbulence from the Kolmogorov 4/5-law and alignment.}, journal = {Philosophical transactions. Series A, Mathematical, physical, and engineering sciences}, volume = {380}, number = {2226}, pages = {20210033}, doi = {10.1098/rsta.2021.0033}, pmid = {35527633}, issn = {1471-2962}, abstract = {A defining feature of three-dimensional hydrodynamic turbulence is that the rate of energy dissipation is bounded away from zero as viscosity is decreased (Reynolds number increased). This phenomenon-anomalous dissipation-is sometimes called the 'zeroth law of turbulence' as it underpins many celebrated theoretical predictions. Another robust feature observed in turbulence is that velocity structure functions [Formula: see text] exhibit persistent power-law scaling in the inertial range, namely [Formula: see text] for exponents [Formula: see text] over an ever increasing (with Reynolds) range of scales. This behaviour indicates that the velocity field retains some fractional differentiability uniformly in the Reynolds number. The Kolmogorov 1941 theory of turbulence predicts that [Formula: see text] for all [Formula: see text] and Onsager's 1949 theory establishes the requirement that [Formula: see text] for [Formula: see text] for consistency with the zeroth law. Empirically, [Formula: see text] and [Formula: see text], suggesting that turbulent Navier-Stokes solutions approximate dissipative weak solutions of the Euler equations possessing (nearly) the minimal degree of singularity required to sustain anomalous dissipation. In this note, we adopt an experimentally supported hypothesis on the anti-alignment of velocity increments with their separation vectors and demonstrate that the inertial dissipation provides a regularization mechanism via the Kolmogorov 4/5-law. This article is part of the theme issue 'Mathematical problems in physical fluid dynamics (part 2)'.}, } @article {pmid35527631, year = {2022}, author = {Parente, E and Farano, M and Robinet, JC and De Palma, P and Cherubini, S}, title = {Continuing invariant solutions towards the turbulent flow.}, journal = {Philosophical transactions. Series A, Mathematical, physical, and engineering sciences}, volume = {380}, number = {2226}, pages = {20210031}, doi = {10.1098/rsta.2021.0031}, pmid = {35527631}, issn = {1471-2962}, abstract = {A new mathematical framework is proposed for characterizing the coherent motion of fluctuations around a mean turbulent channel flow. We search for statistically invariant coherent solutions of the unsteady Reynolds-averaged Navier-Stokes equations written in a perturbative form with respect to the turbulent mean flow, using a suitable approximation of the Reynolds stress tensor. This is achieved by setting up a continuation procedure of known solutions of the perturbative Navier-Stokes equations, based on the continuous increase of the turbulent eddy viscosity towards its turbulent value. The recovered solutions, being sustained only in the presence of the Reynolds stress tensor, are representative of the statistically coherent motion of turbulent flows. For small friction Reynolds number and/or domain size, the statistically invariant motion is almost identical to the corresponding invariant solution of the Navier-Stokes equations. Whereas, for sufficiently large friction number and/or domain size, it considerably departs from the starting invariant solution of the Navier-Stokes equations, presenting spatial structures, main wavelengths and scaling very close to those characterizing both large- and small-scale motion of turbulent channel flows. This article is part of the theme issue 'Mathematical problems in physical fluid dynamics (part 2)'.}, } @article {pmid35523801, year = {2022}, author = {Tretola, G and Vogiatzaki, K}, title = {Unveiling the dynamics of ultra high velocity droplet impact on solid surfaces.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {7416}, pmid = {35523801}, issn = {2045-2322}, support = {EP/S001824/1//Engineering and Physical Sciences Research Council/ ; EP/S001824/1//Engineering and Physical Sciences Research Council/ ; }, abstract = {The impact of a liquid droplet onto a solid surface is a phenomenon present in a wide range of natural processes and technological applications. In this study, we focus on impact conditions characterised by ultra high velocities (up to 500 m/s), to investigate-for the first time-how the impact dynamics change when the compressibility of the liquid in the droplet is no longer negligible. A water droplet impacting a dry substrate at four different velocities, from 50 to 500 m/s, is simulated. Such conditions are particularly relevant to aviation as well as industrial gas turbine engine risk management. Thus, numerical investigations as the one we present here provide a powerful tool to analyse the process. We find that increasing the impact velocity changes the flow field within and outside the droplet the moment that the compressibility can no longer be neglected, with the rise of pressure fronts in both regions. Increasing the impact velocity, the compressibility affects also the lamella formed and changes its ejection velocity observed over time (and thus the wetting behaviour) when the region shift from incompressible to compressible. Moreover, it is found that the maximum pressure observed at the wall during the impact is located at the corner of the impact, where the lamella is ejected, not in the centre, and it is influenced by the initial velocity. To predict the maximum pressure experienced by the surface during the high velocity impact, we propose a correlation based on the initial Weber and Reynolds number of the droplet. The complexity and the scales of the dynamics involved in the ultra-high velocity impact is limiting the experimental and analytical studies. To the best of our knowledge there are no experimental data currently available at such conditions. In this study, through numerical simulations, new insights about the impact dynamics at such conditions are provided.}, } @article {pmid35523157, year = {2022}, author = {D'Adamo, J and Collaud, M and Sosa, R and Godoy-Diana, R}, title = {Wake and aeroelasticity of a flexible pitching foil.}, journal = {Bioinspiration & biomimetics}, volume = {17}, number = {4}, pages = {}, doi = {10.1088/1748-3190/ac6d96}, pmid = {35523157}, issn = {1748-3190}, abstract = {A flexible foil undergoing pitching oscillations is studied experimentally in a wind tunnel with different imposed free stream velocities. The chord-based Reynolds number is in the range 1600-4000, such that the dynamics of the system is governed by inertial forces and the wake behind the foil exhibits the reverse Bénard-von Kármán vortex street characteristic of flapping-based propulsion. Particle image velocimetry (PIV) measurements are performed to examine the flow around the foil, whilst the deformation of the foil is also tracked. The first natural frequency of vibration of the foil is within the range of flapping frequencies explored, determining a strongly-coupled dynamics between the elastic foil deformation and the vortex shedding. Cluster-based reduced order modelling is applied on the PIV data in order to identify the coherent flow structures. Analysing the foil kinematics and using a control-volume calculation of the average drag forces from the corresponding velocity fields, we determine the optimal flapping configurations for thrust generation. We show that propulsive force peaks occur at dimensionless frequencies shifted with respect to the elastic resonances that are marked by maximum trailing edge oscillation amplitudes. The thrust peaks are better explained by a wake resonance, which we examine using the tools of classic hydrodynamic stability on the mean propulsive jet profiles.}, } @article {pmid35522515, year = {2022}, author = {Schindler, F and Eckert, S and Zürner, T and Schumacher, J and Vogt, T}, title = {Collapse of Coherent Large Scale Flow in Strongly Turbulent Liquid Metal Convection.}, journal = {Physical review letters}, volume = {128}, number = {16}, pages = {164501}, doi = {10.1103/PhysRevLett.128.164501}, pmid = {35522515}, issn = {1079-7114}, abstract = {The large-scale flow structure and the turbulent transfer of heat and momentum are directly measured in highly turbulent liquid metal convection experiments for Rayleigh numbers varied between 4×10^{5} and ≤5×10^{9} and Prandtl numbers of 0.025≤Pr≤0.033. Our measurements are performed in two cylindrical samples of aspect ratios Γ=diameter/height=0.5 and 1 filled with the eutectic alloy GaInSn. The reconstruction of the three-dimensional flow pattern by 17 ultrasound Doppler velocimetry sensors detecting the velocity profiles along their beam lines in different planes reveals a clear breakdown of coherence of the large-scale circulation for Γ=0.5. As a consequence, the scaling laws for heat and momentum transfer inherit a dependence on the aspect ratio. We show that this breakdown of coherence is accompanied with a reduction of the Reynolds number Re. The scaling exponent β of the power law Nu∝Ra^{β} crosses eventually over from β=0.221 to 0.124 when the liquid metal flow at Γ=0.5 reaches Ra≳2×10^{8} and the coherent large-scale flow is completely collapsed.}, } @article {pmid35512019, year = {2022}, author = {Fei, L and Qin, F and Zhao, J and Derome, D and Carmeliet, J}, title = {Pore-Scale Study on Convective Drying of Porous Media.}, journal = {Langmuir : the ACS journal of surfaces and colloids}, volume = {38}, number = {19}, pages = {6023-6035}, doi = {10.1021/acs.langmuir.2c00267}, pmid = {35512019}, issn = {1520-5827}, abstract = {In this work, a numerical model for isothermal liquid-vapor phase change (evaporation) of the two-component air-water system is proposed based on the pseudopotential lattice Boltzmann method. Through the Chapman-Enskog multiscale analysis, we show that the model can correctly recover the macroscopic governing equations of the multicomponent multiphase system with a built-in binary diffusion mechanism. The model is verified based on the two-component Stefan problem where the measured binary diffusivity is consistent with theoretical analysis. The model is then applied to convective drying of a dual-porosity porous medium at the pore scale. The simulation captures a classical transition in the drying process of porous media, from the constant rate period (CRP, first phase) showing significant capillary pumping from large to small pores, to the falling rate period (FRP, second phase) with the liquid front receding in small pores. It is found that, in the CRP, the evaporation rate increases with the inflow Reynolds number (Re), while in the FRP, the evaporation curves almost collapse at different Res. The underlying mechanism is elucidated by introducing an effective Péclet number (Pe). It is shown that convection is dominant in the CRP and diffusion in the FRP, as evidenced by Pe > 1 and Pe < 1, respectively. We also find a log-law dependence of the average evaporation rate on the inflow Re in the CRP regime. The present work provides new insights into the drying physics of porous media and its direct modeling at the pore scale.}, } @article {pmid35493567, year = {2021}, author = {Salari, A and Appak-Baskoy, S and Coe, IR and Tsai, SSH and Kolios, MC}, title = {An ultrafast enzyme-free acoustic technique for detaching adhered cells in microchannels.}, journal = {RSC advances}, volume = {11}, number = {52}, pages = {32824-32829}, pmid = {35493567}, issn = {2046-2069}, abstract = {Adherent cultured cells are widely used biological tools for a variety of biochemical and biotechnology applications, including drug screening and gene expression analysis. One critical step in culturing adherent cells is the dissociation of cell monolayers into single-cell suspensions. Different enzymatic and non-enzymatic methods have been proposed for this purpose. Trypsinization, the most common enzymatic method for dislodging adhered cells, can be detrimental to cells, as it can damage cell membranes and ultimately cause cell death. Additionally, all available techniques require a prolonged treatment duration, typically on the order of minutes (5-10 min). Dissociation of cells becomes even more challenging in microfluidic devices, where, due to the nature of low Reynolds number flow and reduced mixing efficiency, multiple washing steps and prolonged trypsinization may be necessary to treat all cells. Here, we report a novel acoustofluidic method for the detachment of cells adhered onto a microchannel surface without exposing the cells to any enzymatic or non-enzymatic chemicals. This method enables a rapid (i.e., on the order of seconds), cost-effective, and easy-to-operate cell detachment strategy, yielding a detachment efficiency of ∼99% and cellular viability similar to that of the conventional trypsinization method. Also, as opposed to biochemical-based techniques (e.g., enzymatic), in our approach, cells are exposed to the dissociating agent (i.e., substrate-mediated acoustic excitation and microstreaming flow) only for as long as they remain attached to the substrate. After dissociation, the effect of acoustic excitation is reduced to microstreaming flow, therefore, minimizing unwanted effects of the dissociating agent on the cell phenotype. Additionally, our results suggest that cell excitation at acoustic powers lower than that required for complete cell detachment can potentially be employed for probing the adhesion strength of cell-substrate attachment. This novel approach can, therefore, be used for a wide range of lab-on-a-chip applications.}, } @article {pmid35489898, year = {2022}, author = {Das, A and Styslinger, M and Harris, DM and Zenit, R}, title = {Force and torque-free helical tail robot to study low Reynolds number micro-organism swimming.}, journal = {The Review of scientific instruments}, volume = {93}, number = {4}, pages = {044103}, doi = {10.1063/5.0079815}, pmid = {35489898}, issn = {1089-7623}, mesh = {Models, Biological ; *Robotics ; *Swimming/physiology ; Torque ; Viscosity ; }, abstract = {Helical propulsion is used by many micro-organisms to swim in viscous-dominated environments. Their swimming dynamics are relatively well understood, but a detailed study of the flow fields is still needed to understand wall effects and hydrodynamic interactions among swimmers. In this letter, we describe the development of an autonomous swimming robot with a helical tail that operates in the Stokes regime. The device uses a battery-based power system with a miniature motor that imposes a rotational speed on a helical tail. The speed, direction, and activation are controlled electronically using an infrared remote control. Since the robot is about 5 cm long, we use highly viscous fluids to match the Reynolds number, Re, to be less than 0.1. Measurements of swimming speeds are conducted for a range of helical wavelengths, λ, head geometries, and rotation rates, ω. We provide comparisons of the experimental measurements with analytical predictions derived from resistive force theory. This force and torque-free neutrally buoyant swimmer mimics the swimming strategy of bacteria more closely than previously used designs and offers a lot of potential for future applications.}, } @article {pmid35489862, year = {2022}, author = {Prasad, V and Kulkarni, SS and Sharma, A}, title = {Chaotic advection in a recirculating flow: Effect of a fluid-flexible-solid interaction.}, journal = {Chaos (Woodbury, N.Y.)}, volume = {32}, number = {4}, pages = {043122}, doi = {10.1063/5.0079141}, pmid = {35489862}, issn = {1089-7682}, abstract = {The present work is on laminar recirculating flow-induced deformation as well as motion of a neutrally buoyant flexible elliptical solid, resulting in Lagrangian chaos in a two-dimensional lid-driven cavity flow. Using a fully Eulerian and monolithic approach-based single-solver for the fluid flow and flexible-solid deformation, a chaotic advection study is presented for various aspect ratios β (=0.5-1.0) and a constant volume fraction Φ=10% of an elliptical solid at a constant Ericksen number Er=0.05 and Reynolds number Re=100. Our initial analysis reveals maximum chaotic advection at β=0.5 for which a comprehensive nonlinear dynamical analysis is presented. The Poincaré map revealed elliptic islands and chaotic sea in the fluid flow. Three large elliptic islands, apart from certain smaller islands, were identified near the solid. Periodic point analysis revealed the lowest order hyperbolic/elliptic periodic points to be three. Adaptive material tracking gave a physical picture of a deforming material blob revealing its exponential stretch along with steep folds and demonstrated unstable/stable manifolds corresponding to lowest order hyperbolic points. Furthermore, adaptive material tracking demonstrates heteroclinic connections and tangles in the system that confirm the existence of chaos. For the transient as compared to the periodic flow, adaptive material tracking demonstrates a larger exponential increase of the blob's interfacial area. The finite-time Lyapunov exponent field revealed attracting/repelling Lagrangian coherent structures and entrapped fluid zones. Our work demonstrates an immersed deformable solid-based onset of chaotic advection, for the first time in the literature, which is relevant to a wide range of applications.}, } @article {pmid35487201, year = {2022}, author = {Akanyeti, O and Di Santo, V and Goerig, E and Wainwright, DK and Liao, JC and Castro-Santos, T and Lauder, GV}, title = {Fish-inspired segment models for undulatory steady swimming.}, journal = {Bioinspiration & biomimetics}, volume = {17}, number = {4}, pages = {}, doi = {10.1088/1748-3190/ac6bd6}, pmid = {35487201}, issn = {1748-3190}, support = {R01 DC010809/DC/NIDCD NIH HHS/United States ; }, mesh = {Animals ; Biological Evolution ; Biomechanical Phenomena/physiology ; *Fishes/physiology ; Hydrodynamics ; *Swimming/physiology ; }, abstract = {Many aquatic animals swim by undulatory body movements and understanding the diversity of these movements could unlock the potential for designing better underwater robots. Here, we analyzed the steady swimming kinematics of a diverse group of fish species to investigate whether their undulatory movements can be represented using a series of interconnected multi-segment models, and if so, to identify the key factors driving the segment configuration of the models. Our results show that the steady swimming kinematics of fishes can be described successfully using parsimonious models, 83% of which had fewer than five segments. In these models, the anterior segments were significantly longer than the posterior segments, and there was a direct link between segment configuration and swimming kinematics, body shape, and Reynolds number. The models representing eel-like fishes with elongated bodies and fishes swimming at high Reynolds numbers had more segments and less segment length variability along the body than the models representing other fishes. These fishes recruited their anterior bodies to a greater extent, initiating the undulatory wave more anteriorly. Two shape parameters, related to axial and overall body thickness, predicted segment configuration with moderate to high success rate. We found that head morphology was a good predictor of its segment length. While there was a large variation in head segments, the length of tail segments was similar across all models. Given that fishes exhibited variable caudal fin shapes, the consistency of tail segments could be a result of an evolutionary constraint tuned for high propulsive efficiency. The bio-inspired multi-segment models presented in this study highlight the key bending points along the body and can be used to decide on the placement of actuators in fish-inspired robots, to model hydrodynamic forces in theoretical and computational studies, or for predicting muscle activation patterns during swimming.}, } @article {pmid35481832, year = {2022}, author = {Hu, S and Zhang, J and Shelley, MJ}, title = {Enhanced clamshell swimming with asymmetric beating at low Reynolds number.}, journal = {Soft matter}, volume = {18}, number = {18}, pages = {3605-3612}, doi = {10.1039/d2sm00292b}, pmid = {35481832}, issn = {1744-6848}, abstract = {A single flexible filament can be actuated to escape from the scallop theorem and generate net propulsion at low Reynolds number. In this work, we study the dynamics of a simple boundary-driven multi-filament swimmer, a two-arm clamshell actuated at the hinged point, using a nonlocal slender body approximation with hydrodynamic interactions. We first consider an elastic clamshell consisted of flexible filaments with intrinsic curvature, and then build segmental models consisted of rigid segments connected by different mechanical joints with different forms of response torques. The simplicity of the system allows us to fully explore the effect of various parameters on the swimming performance. Optimal included angles and elastoviscous numbers are identified. The segmental models capture the characteristic dynamics of the elastic clamshell. We further demonstrate how the swimming performance can be significantly enhanced by the asymmetric beating patterns induced by biased torques.}, } @article {pmid35478056, year = {2022}, author = {Kotnurkar, A and Kallolikar, N}, title = {Effect of Joule heating and entropy generation on multi-slip condition of peristaltic flow of Casson nanofluid in an asymmetric channel.}, journal = {Journal of biological physics}, volume = {48}, number = {3}, pages = {273-293}, pmid = {35478056}, issn = {1573-0689}, mesh = {Entropy ; *Heating ; Hot Temperature ; *Nanoparticles ; Peristalsis/physiology ; }, abstract = {In the present investigation, the effect of multi-slip condition on peristaltic flow through asymmetric channel with Joule heating effect is considered. We also considered the incompressible non-Newtonian Casson nanofluid model for blood, which is electrically conducting. Second law of thermodynamics is used to examine the entropy generation. Multi-slip condition is used at the boundary of the wall and the analysis is also restricted under the low Reynolds number and long wavelength assumption. The governing equations were transformed into a non-dimensional form by using suitable terms. The reduced non-dimensional highly nonlinear partial differential equations are solved by using the Homotopy Perturbation Sumudu transformation method (HPSTM). The influence of different physical parameters on dimensionless velocity, pressure gradient, temperature, concentration and nanoparticle is graphically presented. From the results, one can understand that the Joule heating effect controls the heat transfer in the system and as the magnetic parameter is increased, there will be decay in the velocity of fluid. The outcomes of the present investigation can be applicable in examining the chyme motion in the gastrointestinal tract and controlling the blood flow during surgery. Present study shows an excellent agreement with the previously available studies in the limiting case.}, } @article {pmid35460986, year = {2022}, author = {Liu, J and Yang, Z and Li, M and Lu, K and Li, D}, title = {Evaluating the concrete grade-control structures built by modified fish-nest bricks in the river restoration: A lab-based case study.}, journal = {Journal of environmental management}, volume = {314}, number = {}, pages = {115056}, doi = {10.1016/j.jenvman.2022.115056}, pmid = {35460986}, issn = {1095-8630}, mesh = {Animals ; Ecosystem ; *Fishes ; *Rivers ; Water ; }, abstract = {Concrete grade-control structures (CGCSs) have broad application prospects in the restoration of large rivers. But there is a lack of indicators to evaluate CGCSs at laboratory study. In this study, we proposed two evaluation indicators from the perspective of the impact of CGCSs on geomorphology change and fish habitat, namely the spatial-averaged occurrence probability of sweep events near the bed and flow diversity. To verify the reasonableness of these indicators, flume experiments were conducted with CGCSs built by modified fish-nest bricks in different Reynolds number and layout condition. Data of the flow field around structures in streamwise, transverse and vertical direction was obtained and analyzed. Results of mean flow field show that large recirculation zones are found in the cavity and behind the element. The mechanism of suspended sediment deposition around CGCSs in the flow can be further clarified by combining sweep and ejection according to quadrant analysis. In the vertical direction, the ratio of sweep to total events near bed after spatial-averaged processing is found to be higher for the staggered array. According to the Shannon's entropy, water flow diversity was calculated to quantify the fish habitat. The water flow diversity index around the CGCSs is higher for the staggered. It can be concluded that the elements of CGCSs in staggered manners have a better protection for riverbed and can provide a more stable fish habitat suitability. The results anticipated by the spatial-averaged occurrence probability of sweep events near bed and flow diversity in the experiment are consistent with the result of previous research on landform change and fish habitat. The research could provide a theoretical basis for the application of CGCSs for river restoration.}, } @article {pmid35457904, year = {2022}, author = {Martin, E and Valeije, A and Sastre, F and Velazquez, A}, title = {Impact of Channels Aspect Ratio on the Heat Transfer in Finned Heat Sinks with Tip Clearance.}, journal = {Micromachines}, volume = {13}, number = {4}, pages = {}, pmid = {35457904}, issn = {2072-666X}, abstract = {A 3D numerical study is used to analyze the flow topology and performance, in terms of heat transfer efficiency and required pumping power, of heat sink devices with different channel aspect-ratio in the presence of tip-clearance. Seven different channel aspect ratios AR, from 0.25 to 1.75, were analyzed. The flow Reynolds numbers Re, based on the average velocity evaluated in the device channels region, were in the range of 200 to 1000. Two different behaviors of the global Nusselt were obtained depending on the flow Reynolds number: for Re<600, the heat transfer increased with the channels aspect ratio, e.g., for Re=400, the global Nusselt number increased by 14% for configuration AR=1.75 when compared to configuration AR=0.25. For Re>600, the maximum Nusselt is obtained for the squared-channel configuration, and, for some configurations, flow destabilization to a unsteady regime appeared. For Re=700, Nusselt number reduced when compared with the squared-channel device, 11% and 2% for configurations with AR=0.25 and 1.75, respectively. Dimensionless pressure drop decreased with the aspect ratio for all cases. In the context of micro-devices, where the Reynolds number is small, these results indicate that the use of channels with high aspect-ratios is more beneficial, both in terms of thermal and dynamic efficiency.}, } @article {pmid35454454, year = {2022}, author = {Ayub, R and Ahmad, S and Ahmad, S and Akhtar, Y and Alam, MM and Mahmoud, O}, title = {Numerical Assessment of Dipole Interaction with the Single-Phase Nanofluid Flow in an Enclosure: A Pseudo-Transient Approach.}, journal = {Materials (Basel, Switzerland)}, volume = {15}, number = {8}, pages = {}, pmid = {35454454}, issn = {1996-1944}, abstract = {Nanofluids substantially enhance the physical and thermal characteristics of the base or conducting fluids specifically when interacting with the magnetic field. Several engineering processes like geothermal energy extraction, metal casting, nuclear reactor coolers, nuclear fusion, magnetohydrodynamics flow meters, petrochemicals, and pumps incorporate magnetic field interaction with the nanofluids. On the other hand, an enhancement in heat transfer due to nanofluids is essentially required in various thermal systems. The goal of this study is to figure out that how much a magnetic field affects nanofluid flow in an enclosure because of a dipole. The nanofluid is characterized using a single-phase model, and the governing partial differential equations are computed numerically. A Pseudo time based numerical algorithm is developed to numerically solve the problem. It can be deduced that the Reynolds number and the magnetic parameter have a low effect on the Nusselt number and skin friction. The Nusselt number rises near the dipole location because of an increase in the magnetic parameter Mn and the Reynolds number Re. The imposed magnetic field alters the region of high temperature nearby the dipole, while newly generated vortices rotate in alternate directions. Furthermore, nanoparticle volume fraction causes a slight change in the skin friction while it marginally reduces the Nusselt number.}, } @article {pmid35448318, year = {2022}, author = {Chandrasekaran, AS and Fix, AJ and Warsinger, DM}, title = {Combined Membrane Dehumidification with Heat Exchangers Optimized Using CFD for High Efficiency HVAC Systems.}, journal = {Membranes}, volume = {12}, number = {4}, pages = {}, pmid = {35448318}, issn = {2077-0375}, support = {CHPB-50-2020//Purdue Center for High Performance Buildings/ ; }, abstract = {Traditional air conditioning systems use a significant amount of energy on dehumidification by condensing water vapor out from the air. Membrane-based air conditioning systems help overcome this problem by avoiding condensation and treating the sensible and latent loads separately, using membranes that allow water vapor transport, but not air (nitrogen and oxygen). In this work, a computational fluid dynamics (CFD) model has been developed to predict the heat and mass transfer and concentration polarization performance of a novel active membrane-based energy exchanger (AMX). The novel design is the first of its kind to integrate both vapor removal via membranes and air cooling into one device. The heat transfer results from the CFD simulations are compared with common empirical correlations for similar geometries. The performance of the AMX is studied over a broad range of operating conditions using the compared CFD model. The results show that strong tradeoffs result in optimal values for the channel length (0.6-0.8 m) and the ratio of coil diameter to channel height (~0.5). Water vapor transport is best if the flow is just past the turbulence transition around 3000-5000 Reynolds number. These trends hold over a range of conditions and dimensions.}, } @article {pmid35446443, year = {2022}, author = {Torres-Saucedo, OL and Morales-Cruzado, B and Pérez-Gutiérrez, FG}, title = {Experimental determination of shear stresses on an artificial transcoelomic metastasis model using optical tweezers: A comparison with numerical simulation.}, journal = {Lasers in surgery and medicine}, volume = {54}, number = {7}, pages = {1027-1037}, doi = {10.1002/lsm.23554}, pmid = {35446443}, issn = {1096-9101}, mesh = {Blood Flow Velocity ; Computer Simulation ; Humans ; *Neoplasms ; *Optical Tweezers ; Stress, Mechanical ; }, abstract = {BACKGROUND: One of the reported pathways of cancer spread is the transcoelomic pathway, which is understood as the spread of cancer cells in the abdominal and thoracic cavities through interstitial fluid. It has been proven that the shear stresses caused by microfluidic currents on cancer tumors in the abdominal and thoracic cavities cause the detachment of cancer cells triggering transcoelomic metastasis; however, the magnitude of shear stresses has not yet been measured experimentally.

OBJECTIVES: The objective of this study is to develop an experimental methodology using optical tweezers to approximate the shear stresses suffered by a nonporous, rigid artificial cancerous nodule model.

METHODS: Artificial cancerous nodule model was made by the agglomeration of 2 μm diameter polystyrene particles in a microfluidic platform. Optical tweezers were used as a velocimetry tool and shear stresses on the surface of the nodule model were approximated with the viscous shear stress equation. The results were verified with a numerical simulation performed in Ansys Fluent.

RESULTS: Shear stress originated by microflow over artificial cancerous nodule model were quantified both experimentally and numerically, showing good agreement between both methods. Such stress on the nodules' surface was much greater than that suffered by the wall on which the nodule model was located and dependent of the nodule model geometry. Although the experiment and simulation of this study were performed using a rigid and nonporous nodule model, the conclusion obtained about the increase of shear stresses applies to permeable, porous, and soft nodules as well, because the shear stresses are associated to the acceleration of the fluid originated by the reduction of the cross-sectional area.

CONCLUSIONS: Shear stress over artificial nodule model were successfully quantified using optical tweezer-based velocimetry technique and verified through numerical calculation. Advantages of experimental technique are: (1) it allows to control the position in a three-dimensional plane, allowing measurements in the vicinity of the analyzed surfaces, and (2) it is applicable for very low Reynolds number (Re « 1). On the other hand, as disadvantages: (1) it tends to be complicated to perform velocity measurements over obstacles and (2) it is limited in trapping distance.}, } @article {pmid35436159, year = {2023}, author = {Ibrahim, MG}, title = {Numerical simulation to the activation energy study on blood flow of seminal nanofluid with mixed convection effects.}, journal = {Computer methods in biomechanics and biomedical engineering}, volume = {26}, number = {3}, pages = {315-325}, doi = {10.1080/10255842.2022.2063018}, pmid = {35436159}, issn = {1476-8259}, mesh = {*Convection ; Computer Simulation ; Viscosity ; Motion ; *Body Fluids ; }, abstract = {This study sheds light on the influences of Arrhenius activation energy and variable velocity slip on MHD blood motion of Seminal nanofluid in a vertical symmetric channel. In addition, mixed convection, hall current and thermal jump are taken into consideration. The governing system of differential equations with highly nonlinear terms is simplified with facts of long wavelength and low Reynolds number. Pade' approximant and differential transform techniques are combined mathematically to obtain the semi-numerical solutions for the governing system of PDEs. The results are computed and verified graphically with aid of Mathematica 12.3. Physical parameters considered are studied in detail sketchily for the proposed model. Verification/signification of results is approved semi-numerically by comparing the prior results by the newest existing published results by Ahmad et al 2021. Results show that, Velocity of seminal fluid is diminishes with a rise in viscosity-dependent parameter that is a significant feature which can be utilized in controlling the transport of spermatozoa into the cervical canal.}, } @article {pmid35428793, year = {2022}, author = {Koo, D and So, H}, title = {Facile microfabrication of three dimensional-patterned micromixers using additive manufacturing technology.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {6346}, pmid = {35428793}, issn = {2045-2322}, mesh = {Computer Simulation ; Equipment Design ; *Lab-On-A-Chip Devices ; *Microtechnology ; Printing, Three-Dimensional ; }, abstract = {This study investigates the manufacturing method of oblique patterns in microchannels and the effect of these patterns on mixing performance in microchannels. To fabricate three-dimensional (3D) and oblique patterns in microchannels, 3D printing and replica methods were utilized to mold patterns and microchannels, respectively. The angle and size of the patterns were controlled by the printing angle and resolution, respectively. The mixing efficiency was experimentally characterized, and the mixing principle was analyzed using computational fluid dynamics simulation. The analysis showed that the mixing channel cast from the mold printed with a printing angle of 30° and resolution of 300 μm exhibited the best mixing efficiency with a segregation index of approximately 0.05 at a Reynolds number of 5.4. This was because, as the patterns inside the microchannel were more oblique, "split" and "recombine" behaviors between two fluids were enhanced owing to the geometrical effect. This study supports the use of the 3D printing method to create unique patterns inside microchannels and improve the mixing performance of two laminar flows for various applications such as point-of-care diagnostics, lab-on-a-chip, and chemical synthesis.}, } @article {pmid35428381, year = {2022}, author = {Ilg, P}, title = {Multiparticle collision dynamics for ferrofluids.}, journal = {The Journal of chemical physics}, volume = {156}, number = {14}, pages = {144905}, doi = {10.1063/5.0087981}, pmid = {35428381}, issn = {1089-7690}, abstract = {Detailed studies of the intriguing field-dependent dynamics and transport properties of confined flowing ferrofluids require efficient mesoscopic simulation methods that account for fluctuating ferrohydrodynamics. Here, we propose such a new mesoscopic model for the dynamics and flow of ferrofluids, where we couple the multi-particle collision dynamics method as a solver for the fluctuating hydrodynamics equations to the stochastic magnetization dynamics of suspended magnetic nanoparticles. This hybrid model is validated by reproducing the magnetoviscous effect in Poiseuille flow, obtaining the rotational viscosity in quantitative agreement with theoretical predictions. We also illustrate the new method for the benchmark problem of flow around a square cylinder. Interestingly, we observe that the length of the recirculation region is increased, whereas the drag coefficient is decreased in ferrofluids when an external magnetic field is applied compared with the field-free case at the same effective Reynolds number. The presence of thermal fluctuations and the flexibility of this particle-based mesoscopic method provide a promising tool to investigate a broad range of flow phenomena of magnetic fluids, and the method could also serve as an efficient way to simulate solvent effects when colloidal particles are immersed in ferrofluids.}, } @article {pmid35428147, year = {2022}, author = {Nagy, PT}, title = {Enstrophy change of the Reynolds-Orr solution in channel flow.}, journal = {Physical review. E}, volume = {105}, number = {3-2}, pages = {035108}, doi = {10.1103/PhysRevE.105.035108}, pmid = {35428147}, issn = {2470-0053}, abstract = {The plane Poiseuille flow is one of the elementary flow configurations. Although its laminar-turbulent transition mechanism has been investigated intensively in the last century, the significant difference in the critical Reynolds number between the experiments and the theory lacks a clear explanation. In this paper, an attempt is made to reduce this gap by analyzing the solution of the Reynolds-Orr equation. Recent published results have shown that the usage of enstrophy (the volume integral of the squared vorticity) instead of the kinetic energy as the norm of perturbations predicts higher Reynolds numbers in the two-dimensional case. In addition, other research show has shown an improvement of the original Reynolds-Orr energy equation using the weighted norm in a tilted coordinate system. In this paper the enstrophy is used in three dimensions combined with the tilted coordinate system approach. The zero-enstrophy-growth constraint is applied to the classical Reynolds-Orr equation, and then the solution is further refined in the tilted coordinate system. The results are compared to direct numerical simulations published previously.}, } @article {pmid35428113, year = {2022}, author = {Steiros, K}, title = {Balanced nonstationary turbulence.}, journal = {Physical review. E}, volume = {105}, number = {3-2}, pages = {035109}, doi = {10.1103/PhysRevE.105.035109}, pmid = {35428113}, issn = {2470-0053}, abstract = {Kolmogorov's 1941 (K41) framework remains central to the understanding of turbulent flows. However, in unsteady turbulence, K41's critical equilibrium assumption is expected to hold in an asymptotic manner, as the Reynolds number and wave numbers tend to infinity, rendering K41 not strictly valid at finite wave numbers. This work proposes a generalization of K41 for out-of-equilibrium effects and cascades far from initial conditions. The main result is a correction to the -5/3 law for out-of-equilibrium eddies, unrelated to intermittency effects. Experimental and numerical evidence is provided in support of the theoretical results.}, } @article {pmid35428103, year = {2022}, author = {Rana, N and Perlekar, P}, title = {Phase ordering, topological defects, and turbulence in the three-dimensional incompressible Toner-Tu equation.}, journal = {Physical review. E}, volume = {105}, number = {3}, pages = {L032603}, doi = {10.1103/PhysRevE.105.L032603}, pmid = {35428103}, issn = {2470-0053}, abstract = {We investigate the phase-ordering dynamics of the incompressible Toner-Tu equation in three dimensions. We show that the phase ordering proceeds via defect merger events and the dynamics is controlled by the Reynolds number Re. At low Re, the dynamics is similar to that of the Ginzburg-Landau equation. At high Re, turbulence controls phase ordering. In particular, we observe a forward energy cascade from the coarsening length scale to the dissipation scale, clustering of defects, and multiscaling in velocity correlations.}, } @article {pmid35420623, year = {2022}, author = {Thurgood, P and Chheang, C and Needham, S and Pirogova, E and Peter, K and Baratchi, S and Khoshmanesh, K}, title = {Generation of dynamic vortices in a microfluidic system incorporating stenosis barrier by tube oscillation.}, journal = {Lab on a chip}, volume = {22}, number = {10}, pages = {1917-1928}, doi = {10.1039/d2lc00135g}, pmid = {35420623}, issn = {1473-0189}, mesh = {Constriction, Pathologic ; Humans ; *Microfluidics/methods ; }, abstract = {Microfluidic systems incorporating sudden expansions are widely used for generation of vortex flow patterns. However, the formation of vortices requires high flow rates to induce inertial effects. Here, we introduce a new method for generating dynamic vortices in microfluidics at low static flow rates. Human blood is driven through a microfluidic channel incorporating a semi-circular stenosis barrier. The inlet tube of the channel is axially oscillated using a computer-controlled audio-speaker. The tube oscillation induces high transient flow rates in the channel, which generates dynamic vortices across the stenosis barrier. The size of the vortices can be modulated by varying the frequency and amplitude of tube oscillation. Various vortex flow patterns can be generated by varying the flow rate. The formation and size of the vortices can be predicted using the Reynolds number of the oscillating tube. We demonstrate the potential application of the system for investigating the adhesion and phagocytosis of circulating immune cells under pathologically high shear rates induced at the stenosis. This approach facilitates the development of versatile and controllable inertial microfluidic systems for performing various cellular assays while operating at low static flow rates and low sample volumes.}, } @article {pmid35407874, year = {2022}, author = {Behura, AK and Mohanty, CP and Singh, MR and Kumar, A and Linul, E and Rajak, DK}, title = {Performance Analysis of Three Side Roughened Solar Air Heater: A Preliminary Investigation.}, journal = {Materials (Basel, Switzerland)}, volume = {15}, number = {7}, pages = {}, pmid = {35407874}, issn = {1996-1944}, abstract = {In recent years, sunlight has been used in several fields such as photovoltaic cells, flat plate collectors, solar cookers, green buildings, and agricultural applications. Improved thermal performance has been seen which comes of three sides absorber plate with glass cover compared to the traditional one. This paper presents the Nusselt (Nu) number, collector efficiency factor (CEF), and collector heat removal factor (CHRF) for the optimal solution of three sides artificially roughened solar air heater. Five input variables such as Reynolds (Re) number, relative roughness pitch, relative roughness height, mass flow rate, and air temperature of the duct are taken into account for improved efficiency optimization of collector, collector heat removal factor, and Nu number. Technique for order of preference by similarity to ideal solution (TOPSIS) technique is used to identify the best alternative amongst a number of performance measures by converting them into an equivalent single variable. Moreover, the results revealed the high accuracy of the CEF, CHRF, and Nu number of 75-80%, 74-78%, and 63-71%, respectively. Meanwhile, it has been also observed that roughness Re number varies between 12,500 and 13,500, and height of relative roughness is 0.0245, including pitch of relative roughness 10 along with the rate of mass flow is 0.041 kg/s.}, } @article {pmid35407169, year = {2022}, author = {Bhatti, MM and Bég, OA and Abdelsalam, SI}, title = {Computational Framework of Magnetized MgO-Ni/Water-Based Stagnation Nanoflow Past an Elastic Stretching Surface: Application in Solar Energy Coatings.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {7}, pages = {}, pmid = {35407169}, issn = {2079-4991}, abstract = {In this article, motivated by novel nanofluid solar energy coating systems, a mathematical model of hybrid magnesium oxide (MgO) and nickel (Ni) nanofluid magnetohydrodynamic (MHD) stagnation point flow impinging on a porous elastic stretching surface in a porous medium is developed. The hybrid nanofluid is electrically conducted, and a magnetic Reynolds number is sufficiently large enough to invoke an induced magnetic field. A Darcy model is adopted for the isotropic, homogenous porous medium. The boundary conditions account for the impacts of the velocity slip and thermal slip. Heat generation (source)/absorption (sink) and also viscous dissipation effects are included. The mathematical formulation has been performed with the help of similarity variables, and the resulting coupled nonlinear dimensionless ordinary differential equations have been solved numerically with the help of the shooting method. In order to test the validity of the current results and the convergence of the solutions, a numerical comparison with previously published results is included. Numerical results are plotted for the effect of emerging parameters on velocity, temperature, magnetic induction, skin friction, and Nusselt number. With an increment in nanoparticle volume fraction of both MgO and Ni nanoparticles, the temperature and thermal boundary layer thickness of the nanofluid are elevated. An increase in the porous medium parameter (Darcy number), velocity slip, and thermal Grashof number all enhance the induced magnetic field. Initial increments in the nanoparticle volume fraction for both MgO and Ni suppress the magnetic induction near the wall, although, subsequently, when further from the wall, this effect is reversed. Temperature is enhanced with heat generation, whereas it is depleted with heat absorption and thermal slip effects. Overall, excellent thermal enhancement is achieved by the hybrid nanofluid.}, } @article {pmid35401713, year = {2022}, author = {Fang, L and Li, H and Li, B}, title = {Dynamic Analysis of Deep Water Highway Tunnel under Ocean Current.}, journal = {Computational intelligence and neuroscience}, volume = {2022}, number = {}, pages = {9551792}, pmid = {35401713}, issn = {1687-5273}, abstract = {Comprehensively comparing the merits and demerits of the existing means of transportation across the water, a new underwater transportation structure for crossing the wide water area, named as "deep water highway tunnel" (hereinafter called "DWHT"), is proposed. The characteristics of flow field around the typical section of DWHT at different flow velocities are investigated, which can provide reference for the values of hydrodynamic coefficient at high Reynolds number. The vibration modes and natural by the sound-solid coupling method. In addition, considering the factors of fluid-structure coupling, the dynamic response of displacement and internal force is analyzed based on CFD for the weak parts of the structure. The results show that the deepening of water and the increase of flow will significantly increase the flow field pressure and structure stress, and when the span (or width-span ratio) of the tunnel body extends beyond a certain range, the dynamic characteristics and dynamic response rules of the structure will change.}, } @article {pmid35393485, year = {2022}, author = {Ghorbani, N and Targhi, MZ and Heyhat, MM and Alihosseini, Y}, title = {Investigation of wavy microchannel ability on electronic devices cooling with the case study of choosing the most efficient microchannel pattern.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {5882}, pmid = {35393485}, issn = {2045-2322}, abstract = {A numerical study was conducted to investigate the ability of wavy microchannels to damp the temperature fluctuations generates in electronic devices. Five wavy patterns are considered with the amplitude and wavelength in the ranges of 62.5 to 250 μm and 1250 to 5000 μm, respectively to study the effect of governing phenomena of flow within wavy patterns on thermal-hydraulic performance. The flow regime is laminar and the Reynolds number is in the range of 300 to 900, and a relatively high heat flux of 80 W/cm[2] is applied to the microchannels substrate. Also, variable flux condition is studied for heat fluxes of 80, 120, 160, 200, and 240 W/cm[2] and for the most efficient wavy and straight microchannels. Results showed that the geometries with larger amplitude to wavelength ratio have a lower radius of curvature and larger Dean number, and as a result of transverse flow (secondary flow) amplification, they have enhanced heat transfer. Also, by comparing the ratio of the transverse velocity components to the axial component, it was found that by decreasing the radius of curvature and increasing the Dean number, transverse velocity increases, which intensifies the heat transfer between the wall and the fluid. The appraisement of the performance evaluation criterion (PEC) illustrates that the wavy case with an amplitude of 250 μm and wavelength of 2500 μm is the best geometry from the thermal-hydraulic point of view in the studied range. Finally, with variable flux condition, the wavy microchannel has responded well to the temperature increase and has created a much more uniform surface temperature compared to straight pattern. The proposed wavy pattern ensures that there are no hotspots which could damage the electronic chip. Presented wavy patterns can be used in heat sinks heat transfer enhancement to allow the chip to run in higher heat fluxes.}, } @article {pmid35390073, year = {2022}, author = {Almerol, JLO and Liponhay, MP}, title = {Clustering of fast gyrotactic particles in low-Reynolds-number flow.}, journal = {PloS one}, volume = {17}, number = {4}, pages = {e0266611}, pmid = {35390073}, issn = {1932-6203}, mesh = {Cluster Analysis ; Computer Simulation ; *Hydrodynamics ; Physical Phenomena ; *Swimming ; }, abstract = {Systems of particles in turbulent flows exhibit clustering where particles form patches in certain regions of space. Previous studies have shown that motile particles accumulate inside the vortices and in downwelling regions, while light and heavy non-motile particles accumulate inside and outside the vortices, respectively. While strong clustering is generated in regions of high vorticity, clustering of motile particles is still observed in fluid flows where vortices are short-lived. In this study, we investigate the clustering of fast swimming particles in a low-Reynolds-number turbulent flow and characterize the probability distributions of particle speed and acceleration and their influence on particle clustering. We simulate gyrotactic swimming particles in a cubic system with homogeneous and isotropic turbulent flow. Here, the swimming velocity explored is relatively faster than what has been explored in other reports. The fluid flow is produced by conducting a direct numerical simulation of the Navier-Stokes equation. In contrast with the previous results, our results show that swimming particles can accumulate outside the vortices, and clustering is dictated by the swimming number and is invariant with the stability number. We have also found that highly clustered particles are sufficiently characterized by their acceleration, where the increase in the acceleration frequency distribution of the most clustered particles suggests a direct influence of acceleration on clustering. Furthermore, the acceleration of the most clustered particles resides in acceleration values where a cross-over in the acceleration PDFs are observed, an indicator that particle acceleration generates clustering. Our findings on motile particles clustering can be applied to understanding the behavior of faster natural or artificial swimmers.}, } @article {pmid35389496, year = {2022}, author = {Letendre, F and Cameron, CB}, title = {The capture of crude oil droplets by filter feeders at high and low Reynolds numbers.}, journal = {The Journal of experimental biology}, volume = {225}, number = {8}, pages = {}, doi = {10.1242/jeb.243819}, pmid = {35389496}, issn = {1477-9145}, support = {RGPIN/05058-2017//Natural Sciences and Engineering Research Council of Canada/ ; //Natural Sciences and Engineering Research Council of Canada/ ; }, mesh = {Animals ; Daphnia ; Food Chain ; *Petroleum ; *Petroleum Pollution ; *Thoracica ; }, abstract = {Crustacean filter feeders capture oil droplets with the use of their ramified appendages. These appendages behave as paddles or sieves, based on the system's Reynolds number. Here, we used high-speed videography, scanning electron microscopy and fluid mechanics to study the capturing mechanisms of crude oil droplets and the filtering appendage's wettability by two species of barnacles (Balanus glandula and Balanus crenatus) and of the freshwater cladoceran Daphnia magna. Our results show that barnacle appendages behave as paddles and capture droplets in their boundary layers at low Reynolds number. At high Reynolds number, droplets are most likely to be captured via direct interception. There is an intermediate range of Reynolds number where droplets can be captured by both mechanisms at the same time. Daphnia magna captures droplets in the boundary layers of the third and fourth pair of thoracic legs with a metachronal motion of the appendages. All studied surfaces were revealed to be highly lipophobic, demonstrating captured oil droplets with high contact angles. We also discuss implications of such capture mechanisms and wettability on potential ingestion of crude oil by filter feeders. These results further our understanding of the capture of crude oil by filter feeders, shedding light on the main entry point of oil in marine food webs.}, } @article {pmid35385160, year = {2022}, author = {Wang, J and Dong, Y and Ma, P and Wang, Y and Zhang, F and Cai, B and Chen, P and Liu, BF}, title = {Intelligent Micro-/Nanorobots for Cancer Theragnostic.}, journal = {Advanced materials (Deerfield Beach, Fla.)}, volume = {34}, number = {52}, pages = {e2201051}, doi = {10.1002/adma.202201051}, pmid = {35385160}, issn = {1521-4095}, support = {2021YFA1101500//National Key R&D Program of China/ ; 22074047//National Natural Science Foundation of China/ ; 21775049//National Natural Science Foundation of China/ ; }, mesh = {Humans ; *Neoplasms/diagnostic imaging/therapy ; Drug Delivery Systems/methods ; *Nanoparticles/therapeutic use ; }, abstract = {Cancer is one of the most intractable diseases owing to its high mortality rate and lack of effective diagnostic and treatment tools. Advancements in micro-/nanorobot (MNR)-assisted sensing, imaging, and therapeutics offer unprecedented opportunities to develop MNR-based cancer theragnostic platforms. Unlike ordinary nanoparticles, which exhibit Brownian motion in biofluids, MNRs overcome viscous resistance in an ultralow Reynolds number (Re << 1) environment by effective self-propulsion. This unique locomotion property has motivated the advanced design and functionalization of MNRs as a basis for next-generation cancer-therapy platforms, which offer the potential for precise distribution and improved permeation of therapeutic agents. Enhanced barrier penetration, imaging-guided operation, and biosensing are additionally studied to enable the promising cancer-related applications of MNRs. Herein, the recent advances in MNR-based cancer therapy are comprehensively addresses, including actuation engines, diagnostics, medical imaging, and targeted drug delivery; promising research opportunities that can have a profound impact on cancer therapy over the next decade is highlighted.}, } @article {pmid35379035, year = {2022}, author = {Saeed Khan, MW and Ali, N and Bég, OA}, title = {Thermal entrance problem for blood flow inside an axisymmetric tube: The classical Graetz problem extended for Quemada's bio-rheological fluid with axial conduction.}, journal = {Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine}, volume = {236}, number = {6}, pages = {848-859}, doi = {10.1177/09544119221086479}, pmid = {35379035}, issn = {2041-3033}, mesh = {*Algorithms ; *Hemodynamics ; Hot Temperature ; Humans ; Rheology ; Viscosity ; }, abstract = {The heat-conducting nature of blood is critical in the human circulatory system and features also in important thermal regulation and blood processing systems in biomedicine. Motivated by these applications, in the present investigation, the classical Graetz problem in heat transfer is extended to the case of a bio-rheological fluid model. The Quemada bio-rheological fluid model is selected since it has been shown to be accurate in mimicking physiological flows (blood) at different shear rates and hematocrits. The steady two-dimensional energy equation without viscous dissipation in stationary regime is tackled via a separation of variables approach for the isothermal wall temperature case. Following the introduction of transformation variables, the ensuing dimensionless boundary value problem is solved numerically via MATLAB based algorithm known as bvp5c (a finite difference code that implements the four-stage Lobatto IIIa collocation formula). Numerical validation is also presented against two analytical approaches namely, series solutions and Kummer function techniques. Axial conduction in terms of Péclet number is also considered. Typical values of Reynolds number and Prandtl number are used to categorize the vascular regions. The graphical representation of mean temperature, temperature gradient, and Nusselt numbers along with detail discussions are presented for the effects of Quemada non-Newtonian parameters and Péclet number. The current analysis may also have potential applications for the development of microfluidic and biofluidic devices particularly which are used in the diagnosis of diseases in addition to blood oxygenation technologies.}, } @article {pmid35363001, year = {2022}, author = {Tan, S and Ni, R}, title = {Universality and Intermittency of Pair Dispersion in Turbulence.}, journal = {Physical review letters}, volume = {128}, number = {11}, pages = {114502}, doi = {10.1103/PhysRevLett.128.114502}, pmid = {35363001}, issn = {1079-7114}, abstract = {Turbulence can disperse a concentrated parcel of pollutants at a rate over nine orders of magnitude higher than its purely diffusive counterpart. One intriguing signature of turbulent dispersion is its superdiffusive scaling. However, the universality of this scaling law is still in question. By leveraging a new laboratory facility, particle pairs with small initial separations can be tracked over four decades of separation in time and five decades of separation in squared displacement, thereby observing the full range of dispersion scaling laws. The results show that the classical Richardson cubic scaling will be reached not for an initial separation asymptotically close to zero but at a critical value, and this value does not appear to depend on the Reynolds number, providing an effective way to study universal dispersion dynamics. Additionally, the results agree well with the prediction based on the multifractal model and may help reconcile different reported scaling laws from laboratory experiments and field studies.}, } @article {pmid35355005, year = {2022}, author = {Kamdar, S and Shin, S and Leishangthem, P and Francis, LF and Xu, X and Cheng, X}, title = {The colloidal nature of complex fluids enhances bacterial motility.}, journal = {Nature}, volume = {603}, number = {7903}, pages = {819-823}, pmid = {35355005}, issn = {1476-4687}, mesh = {Bacteria ; *Colloids ; *Ecosystem ; Humans ; Hydrodynamics ; Polymers ; }, abstract = {The natural habitats of microorganisms in the human microbiome, ocean and soil ecosystems are full of colloids and macromolecules. Such environments exhibit non-Newtonian flow properties, drastically affecting the locomotion of microorganisms[1-5]. Although the low-Reynolds-number hydrodynamics of swimming flagellated bacteria in simple Newtonian fluids has been well developed[6-9], our understanding of bacterial motility in complex non-Newtonian fluids is less mature[10,11]. Even after six decades of research, fundamental questions about the nature and origin of bacterial motility enhancement in polymer solutions are still under debate[12-23]. Here we show that flagellated bacteria in dilute colloidal suspensions display quantitatively similar motile behaviours to those in dilute polymer solutions, in particular a universal particle-size-dependent motility enhancement up to 80% accompanied by a strong suppression of bacterial wobbling[18,24]. By virtue of the hard-sphere nature of colloids, whose size and volume fraction we vary across experiments, our results shed light on the long-standing controversy over bacterial motility enhancement in complex fluids and suggest that polymer dynamics may not be essential for capturing the phenomenon[12-23]. A physical model that incorporates the colloidal nature of complex fluids quantitatively explains bacterial wobbling dynamics and mobility enhancement in both colloidal and polymeric fluids. Our findings contribute to the understanding of motile behaviours of bacteria in complex fluids, which are relevant for a wide range of microbiological processes[25] and for engineering bacterial swimming in complex environments[26,27].}, } @article {pmid35338884, year = {2022}, author = {Mezali, F and Benmamar, S and Naima, K and Ameur, H and Rafik, O}, title = {Evaluation of stent effect and thrombosis generation with different blood rheology on an intracranial aneurysm by the Lattice Boltzmann method.}, journal = {Computer methods and programs in biomedicine}, volume = {219}, number = {}, pages = {106757}, doi = {10.1016/j.cmpb.2022.106757}, pmid = {35338884}, issn = {1872-7565}, mesh = {Blood Flow Velocity ; Hemodynamics/physiology ; Humans ; *Intracranial Aneurysm/surgery ; Rheology ; Stents ; *Thrombosis/prevention & control ; }, abstract = {BACKGROUND AND OBJECTIVE: Treatment of intracranial aneurysms with flow-diverting stents prevents rupture by reducing blood flow and creating thrombosis within the aneurysm. This paper aims to assess the hemodynamic effect of placing stents with different struts (0, 3, 5, 7 struts) on intracranial aneurysms and to propose a simple prediction model of thrombosis zone without any further computational cost.

METHOD: Lattice Boltzmann method with different rheological models (Newtonian, Carreau-Yasuda, KL) of blood are used to study the hemodynamic effect of flow-diverting stents in the aneurysm. Pulsatile flow boundary conditions were applied in the inlet of the artery. The average Reynolds number was resulting Re = 111. The Lagrangian tracking of the particle was developed to assess the intra-aneurysmal blood stagnation. To predict the probable thrombose zone induced by flow-diverting stents, the shear rate threshold is utilized to determine the nodes of fluid to clot.

RESULTS: The results show that the flow patterns into the aneurysmal sac develop a vortex, decreasing after stent placement until disappearance for the stent with seven struts (porosity 71.4%). Velocity, shear rate, shear stress, trajectory, path length, and occlusion rate are compared before and after stent placement. These parameters decrease inversely with the porosity of the stent. The three models yield a closes result of the (velocity, shear rate, occlusion rate). Tracking the fluid-particle trajectory shows that the length of the particle paths decreases with the number of struts causing fluid to slow down and increase, consequently, the residence time into the sac.

CONCLUSION: The flow-diverting stents placement cause the reduction of dynamic flow within aneurysm. The reduction effect is almost the same below five struts (80% of porosity). The results show that, if our objective is restricted to estimating the hemodynamic effect, measured by (velocity, shear rate, occlusion rate), the differences between rheological behavior models are, practically, not significant, and the models can be used indifferently.}, } @article {pmid35334666, year = {2022}, author = {Nuwairan, MA and Souayeh, B}, title = {Simulation of Gold Nanoparticle Transport during MHD Electroosmotic Flow in a Peristaltic Micro-Channel for Biomedical Treatment.}, journal = {Micromachines}, volume = {13}, number = {3}, pages = {}, pmid = {35334666}, issn = {2072-666X}, support = {Grant No.207021//Deanship of Scientific Research at King Faisal University/ ; }, abstract = {The study of gold nanoparticles (AuNPs) in the blood flow has emerged as an area of interest for numerous researchers, due to its many biomedical applications, such as cancer radiotherapy, DNA and antigens, drug and gene delivery, in vitro evaluation, optical bioimaging, radio sensitization and laser phototherapy of cancer cells and tumors. Gold nanoparticles can be amalgamated in various shapes and sizes. Due to this reason, gold nanoparticles can be diffused efficiently, target the diseased cells and destroy them. The current work studies the effect of gold nanoparticles of different shapes on the electro-magneto-hydrodynamic (EMHD) peristaltic propulsion of blood in a micro-channel under various effects, such as activation energy, bioconvection, radiation and gyrotactic microorganisms. Four kinds of nanoparticle shapes, namely bricks, cylinders and platelets, are considered. The governing equations are simplified under the approximations of low Reynolds number (LRN), long wavelength (LWL) and Debye-Hückel linearization (DHL). The numerical solutions for the non-dimensional equations are solved using the computational software MATLAB with the help of the bvp4c function. The influences of different physical parameters on the flow and thermal characteristics are computed through pictorial interpretations.}, } @article {pmid35329572, year = {2022}, author = {Sawka, A}, title = {Chemical Vapour Deposition of Scandia-Stabilised Zirconia Layers on Tubular Substrates at Low Temperatures.}, journal = {Materials (Basel, Switzerland)}, volume = {15}, number = {6}, pages = {}, pmid = {35329572}, issn = {1996-1944}, support = {16.16.160.557//Subvention of the Polish State Ministry of Education and Science for AGH University of Science and Technology, Faculty of Materials Science and Ceramics/ ; }, abstract = {The paper presents results of investigation on synthesis of non-porous ZrO2-Sc2O2 layers on tubular substrates by MOCVD (metalorganic chemical vapor deposition) method using Sc(tmhd)3 (Tris(2,2,6,6-tetramethyl-3,5-heptanedionato)scandium(III), 99%) and Zr(tmhd)4 (Tetrakis(2,2,6,6-tetramethyl-3,5-heptanedionato)zirconium)(IV), 99.9+%) as basic reactants. The molar content of Sc(tmhd)3 in the gas mixture was as follows: 14, 28%. The synthesis temperature was in the range of 600-700 °C. The value of extended Grx/Rex[2] expression (Gr-Grashof number, Re-Reynolds number and x-the distance from the gas inflow point) was less than 0.01. The layers were deposited under reduced pressure or close to atmospheric pressure. The layers obtained were tested using scanning electron microscope (SEM) with an energy dispersive X-ray spectroscope (EDS) microanalyzer, X-ray diffractometer and UV-Vis spectrophotometer. The layers deposited were non-porous, amorphous or nanocrystalline with controlled chemical composition. The layers synthesized at 700 °C were nanocrystalline. ZrO2-Sc2O3 layers with 14 mol.% Sc2O3 content had a rhombohedral structure.}, } @article {pmid35327926, year = {2022}, author = {Lin, W and Shi, R and Lin, J}, title = {Heat Transfer and Pressure Drop of Nanofluid with Rod-like Particles in Turbulent Flows through a Curved Pipe.}, journal = {Entropy (Basel, Switzerland)}, volume = {24}, number = {3}, pages = {}, pmid = {35327926}, issn = {1099-4300}, support = {12132015//National Natural Science Foundation of China/ ; }, abstract = {Pressure drop, heat transfer, and energy performance of ZnO/water nanofluid with rodlike particles flowing through a curved pipe are studied in the range of Reynolds number 5000 ≤ Re ≤ 30,000, particle volume concentration 0.1% ≤ Φ ≤ 5%, Schmidt number 10[4] ≤ Sc ≤ 3 × 10[5], particle aspect ratio 2 ≤ λ ≤ 14, and Dean number 5 × 10[3] ≤ De ≤ 1.5 × 10[4]. The momentum and energy equations of nanofluid, together with the equation of particle number density for particles, are solved numerically. Some results are validated by comparing with the experimental results. The effect of Re, Φ, Sc, λ, and De on the friction factor f and Nusselt number Nu is analyzed. The results showed that the values of f are increased with increases in Φ, Sc, and De, and with decreases in Re and λ. The heat transfer performance is enhanced with increases in Re, Φ, λ, and De, and with decreases in Sc. The ratio of energy PEC for nanofluid to base fluid is increased with increases in Re, Φ, λ, and De, and with decreases in Sc. Finally, the formula of ratio of energy PEC for nanofluid to base fluid as a function of Re, Φ, Sc, λ, and De is derived based on the numerical data.}, } @article {pmid35327850, year = {2022}, author = {Dou, HS}, title = {No Existence and Smoothness of Solution of the Navier-Stokes Equation.}, journal = {Entropy (Basel, Switzerland)}, volume = {24}, number = {3}, pages = {}, pmid = {35327850}, issn = {1099-4300}, abstract = {The Navier-Stokes equation can be written in a form of Poisson equation. For laminar flow in a channel (plane Poiseuille flow), the Navier-Stokes equation has a non-zero source term (∇[2]u(x, y, z) = Fx (x, y, z, t) and a non-zero solution within the domain. For transitional flow, the velocity profile is distorted, and an inflection point or kink appears on the velocity profile, at a sufficiently high Reynolds number and large disturbance. In the vicinity of the inflection point or kink on the distorted velocity profile, we can always find a point where ∇[2]u(x, y, z) = 0. At this point, the Poisson equation is singular, due to the zero source term, and has no solution at this point due to singularity. It is concluded that there exists no smooth orphysically reasonable solutions of the Navier-Stokes equation for transitional flow and turbulence in the global domain due to singularity.}, } @article {pmid35299996, year = {2022}, author = {Marchello, R and Morandotti, M and Shum, H and Zoppello, M}, title = {The N -Link Swimmer in Three Dimensions: Controllability and Optimality Results.}, journal = {Acta applicandae mathematicae}, volume = {178}, number = {1}, pages = {6}, pmid = {35299996}, issn = {0167-8019}, abstract = {The controllability of a fully three-dimensional N -link swimmer is studied. After deriving the equations of motion in a low Reynolds number fluid by means of Resistive Force Theory, the controllability of the minimal 2-link swimmer is tackled using techniques from Geometric Control Theory. The shape of the 2-link swimmer is described by two angle parameters. It is shown that the associated vector fields that govern the dynamics generate, via taking their Lie brackets, all eight linearly independent directions in the combined configuration and shape space, leading to controllability; the swimmer can move from any starting configuration and shape to any target configuration and shape by operating on the two shape variables. The result is subsequently extended to the N -link swimmer. Finally, the minimal time optimal control problem and the minimization of the power expended are addressed and a qualitative description of the optimal strategies is provided.}, } @article {pmid35297830, year = {2022}, author = {Wang, Y and Zhao, W and Wang, B and Wang, Y}, title = {Prediction model of combustion characteristics of methane-air using hyperspectral imaging.}, journal = {Applied optics}, volume = {61}, number = {7}, pages = {D75-D84}, doi = {10.1364/AO.444118}, pmid = {35297830}, issn = {1539-4522}, abstract = {Hyperspectral imaging can obtain considerable flame information, which can improve the prediction accuracy of combustion characteristics. This paper studies the hyperspectral characteristics of methane flames and proposes several prediction models. The experimental results show that the radiation intensity and radiation types of free radicals are related to the equivalent ratio, and the radiation region of free radicals becomes larger with the increase of the Reynolds number. The polynomial regression prediction models include the linear model and quadratic model. It takes C2∗/CH[∗] as input parameters, and results can be available immediately. The three-dimensional convolutional neural network (3D-CNN) prediction model takes all spectral and spatial information in the flame hyperspectral image as input parameters. By improving the structural parameters of the convolution network, the final prediction errors of the equivalent ratio and Reynolds number are 2.84% and 3.11%, respectively. The method of combining the 3D-CNN model with hyperspectral imaging significantly improves the prediction accuracy, and it can be used to predict other combustion characteristics such as pollutant emissions and combustion efficiency.}, } @article {pmid35291149, year = {2022}, author = {Ma, X and Gong, X and Tang, Z and Jiang, N}, title = {Control of leading-edge separation on bioinspired airfoil with fluttering coverts.}, journal = {Physical review. E}, volume = {105}, number = {2-2}, pages = {025107}, doi = {10.1103/PhysRevE.105.025107}, pmid = {35291149}, issn = {2470-0053}, abstract = {In this work, the aerodynamic role of the artificial covert feathers (i.e., coverts) on an airfoil is experimentally studied in a wind tunnel to investigate the flow control effect on the leading-edge separation. We apply flexible featherlike devices on a high-angle-of-attack airfoil. We use a hot-wire anemometer to measure the velocity profiles and turbulent fluctuations in the downstream wake flow. As a baseline of flow separation, a two-dimensional NACA 0018 airfoil model is set at the angle of attack of 15 ° at the chord-based Reynolds number of 1.0×10^{5}, causing strong leading-edge and trailing-edge shear layers and a low-speed wake flow area in between as large as 0.35 chord length. When deployed on the upper wing surface, the flexible coverts adaptively flutter under the influence of the local unsteady airflow. Hot-wire measurement results show that the leading-edge coverts effectively suppress the flow separation and reduce the size of the wake flow area. The change of power spectral density shows that the predominant peaks as the fundamental and harmonic frequencies are both attenuated due to the suppression of unsteady motions of the shear layers. On the other hand, the fluttering coverts at the trailing edge modify the trailing-edge shear layer by redistributing the turbulent kinetic energy to the high-frequency components. By simultaneous double-point measurement, we find that the leading-edge and trailing-edge shear layers are drawn closer to each other, and the two shear layers show an increased peak in the coherence spectrum. Further multiscale wavelet analysis shows that the perturbations at the 60% chord length increase the large-scale amplitude modulation of small-scale turbulence and therefore they stabilize the leading-edge and trailing-edge shear layers. Meanwhile, the flow intermittency outside of the wake flow area is attenuated as well. The effective flow control effects in the present work are in good agreement with the previous direct observations of bird flight in literature that the coverts on the upper wing surface play an important role in flow separation control during high-angle-of-attack flight. These findings advance the understanding of aerodynamic contribution of the covers on bird wings and reveal the engineering potential of bioinspired coverts for flow separation control of aircrafts and unmanned air vehicles.}, } @article {pmid35270649, year = {2022}, author = {Ovando-Chacon, GE and Rodríguez-León, A and Ovando-Chacon, SL and Hernández-Ordoñez, M and Díaz-González, M and Pozos-Texon, FJ}, title = {Computational Study of Thermal Comfort and Reduction of CO2 Levels inside a Classroom.}, journal = {International journal of environmental research and public health}, volume = {19}, number = {5}, pages = {}, pmid = {35270649}, issn = {1660-4601}, mesh = {*Air Pollution, Indoor/analysis/prevention & control ; *COVID-19/epidemiology ; Carbon Dioxide/analysis ; Humans ; Pandemics ; SARS-CoV-2 ; }, abstract = {Due to the current COVID-19 pandemic, guaranteeing thermal comfort and low CO2 levels in classrooms through efficient ventilation has become vitally important. This study presents three-dimensional simulations based on computational fluid dynamics of airflow inside an air-conditioned classroom located in Veracruz, Mexico. The analysis included various positions of an air extractor, Reynolds numbers up to 3.5 × 10[4], four different concentrations of pollutant sources, and three different times of the day. The simulations produced velocity, air temperature, and CO2 concentrations fields, and we calculated average air temperatures, average CO2 concentrations, and overall ventilation effectiveness. Our results revealed an optimal extractor position and Reynolds number conducive to thermal comfort and low CO2 levels due to an adequate ventilation configuration. At high pollutant concentrations, it is necessary to reduce the number of students in the classroom to achieve safe CO2 levels.}, } @article {pmid35264611, year = {2022}, author = {Memon, AA and Memon, MA and Bhatti, K and Khan, I and Alshammari, N and Al-Johani, AS and Hamadneh, NN and Andualem, M}, title = {Thermal decomposition of propylene oxide with different activation energy and Reynolds number in a multicomponent tubular reactor containing a cooling jacket.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {4169}, pmid = {35264611}, issn = {2045-2322}, abstract = {In this article, we are focusing on heat and mass transfer through a Multicomponent tubular reactor containing a cooling jacket by thermal decomposition of propylene oxide in water. The chemical reaction is an irreversible, 1st order reaction and an exothermic reaction that yields propylene glycol with enthalpy = -84,666 J/mol. The constant rate of the reaction is followed by the Arrhenius equation in which the activation energy is taken on a trial basis in the range from 75,000 to 80,000 J/mol with a fixed frequency factor. For the fluid to flow, the Reynolds number is kept in the range from 100 to 1000. The three partial differential equations of mass, momentum, and energy are coupled to study heat and mass transfer in a tubular reactor by using the chemistry interface in COMSOL Multiphysics 5.4. The initial concentration of propylene oxide is tested in the range from 2 to 3% and the thermal conductivity of the mixture is tested in the range 0.599-0.799. It was found that the amount deactivated of the compound decreases with an increase in Reynolds number. Propylene oxide is decomposed at about 99.8% at Re = 100 at lower activation energy and gives the total maximum enthalpy change in the tubular reactor. Observing the relationship between Sherwood numbers to Nusselt numbers, it was deducted that the convective heat transfer is opposite to convective mass transfer for high Reynolds numbers.}, } @article {pmid35236870, year = {2022}, author = {Khan, Z and Ul Haq, S and Ali, F and Andualem, M}, title = {Free convection flow of second grade dusty fluid between two parallel plates using Fick's and Fourier's laws: a fractional model.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {3448}, pmid = {35236870}, issn = {2045-2322}, abstract = {The paper aims to investigate the channel flow of second grade visco-elastic fluid generated due to an oscillating wall. The effect of heat and mass transfer has been taken into account. The phenomenon has been modelled in terms of PDEs. The constitutive equations are fractionalized by using the definition of the Caputo fractional operator with Fick's and Fourier's Laws. The system of fractional PDEs is non-dimensionalized by using appropriate dimensionless variables. The closed-form solutions of thermal and concentration boundary layers are obtained by using the Laplace and finite Fourier-Sine transforms, while the momentum equation is solved by a numerical approach by Zakian using [Formula: see text]. Furthermore, the parametric influence of various embedded physical parameters on momentum, temperature, and concentration distributions is depicted through various graphs. It is observed that the fractional approach is more convenient and realistic as compared to the classical approach. It is worth noting that the increasing values of [Formula: see text], [Formula: see text] and [Formula: see text] retard the boundary layer profile. For instance, this behaviour of [Formula: see text] is significant where boundary control is necessary. That is, in the case of resonance, the physical solution may be obtained by adding the effect of MHD. The Reynolds number is useful in characterising the transport properties of a fluid or a particle travelling through a fluid. The Reynolds number is one of the main controlling parameters in all viscous flow. It determines whether the fluid flow is laminar or turbulent. The evolution of the rate of heat, mass transfer, and skin friction on the left plate with various physical parameters are presented in tables. These quantities are of high interest for engineers. Keeping in mind the effect of various parameters on these engineering quantities, they make their feasibility reports.}, } @article {pmid35233704, year = {2022}, author = {Cai, C and Wen, C and Guan, L and Huang, Y and Jiang, Q}, title = {Influence of sodium hypochlorite concentration on cavitation effect and fluid dynamics induced by photon-induced photoacoustic streaming (PIPS): A visualization study.}, journal = {Lasers in medical science}, volume = {37}, number = {5}, pages = {2537-2544}, pmid = {35233704}, issn = {1435-604X}, support = {[2017]-210//Guangzhou Medical University/ ; [2017-160]//Guangzhou Medical University/ ; }, mesh = {Dental Pulp Cavity ; Hydrodynamics ; Photons/therapeutic use ; *Root Canal Irrigants/pharmacology ; Root Canal Preparation ; *Sodium Hypochlorite/pharmacology ; }, abstract = {PURPOSE: The aim of the present study was to visualize and compare the cavitation effect and fluid dynamics induced by photon-induced photoacoustic streaming (PIPS) using sodium hypochlorite (NaOCl) with different concentrations as irrigant.

METHODS: Forty artificial root canals were prepared using MTWO Niti file up to size #25/.06. The canals were randomly divided into four groups (n = 10/group). High-speed camera was used to visualize and compare the cavitation effect induced by PIPS in the artificial root canals containing saline or NaOCl. Fluid velocity and Reynolds number of saline, 1%-, 2.5%- and 5.25% NaOCl irrigants induced by PIPS in the apical region were calculated using TEMA 2D software while the fluid motions were recorded.

RESULTS: Visualization profile revealed that NaOCl presented a stronger cavitation effect and fluid dynamics than saline during PIPS activation. In the apical region, 1% NaOCl group presented the highest average velocity of 3.868 m/s, followed by 2.5% NaOCl group (3.685 m/s), 5.25% NaOCl group (2.353 m/s) and saline group (1.268 m/s), corresponding to Reynolds number of 1653.173, 1572.196, 995.503 and 477.692. Statistically higher fluid velocity was calculated in 1% and 2.5% NaOCl groups compared to saline group, respectively (p < 0.05).

CONCLUSIONS: The application of NaOCl and its concentration significantly influence the cavitation effect and fluid dynamics during PIPS activation. 1% and 2.5% NaOCl groups presented a more violent fluid motion in the apical region when activated by PIPS.}, } @article {pmid35232981, year = {2022}, author = {Abd-Alla, AM and Thabet, EN and Bayones, FS}, title = {Numerical solution for MHD peristaltic transport in an inclined nanofluid symmetric channel with porous medium.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {3348}, pmid = {35232981}, issn = {2045-2322}, abstract = {The significance of the study is to determine of transferred heat and mass impact on the magneto-hydrodynamic peristalsis of Jeffery nanofluid through porous media with inclined symmetric channels whose walls are induced by peristaltic motion within porous media. The aim of this investagtion is to study the influence of various types of parameters such as Brownian motion, thermophoresis, buoyancy forces, and magnetic fields are studies on concentration, temperature, and axial velocity. The numerical solution has been achieved according to the long-wavelength and low Reynolds number approximation utilizing the MATLAB bvp4c function. The resultant dimensions of nonlinear governing equations were approached numerically through the Runge-Kutta- Fehlberg integration scheme, a MATLAB program. The influence of different factors such as the ratio of relaxation to retardation times, nanoparticle Grashof number, and magnetic field was discussed on concentration, temperature, and velocity profiles. tables and graphs were used to demonstrate the numerically computed numerical results. Plotting graphs were utilized for evaluating the pertinent parameters impacts on the aforementioned quantities based on computational results. According to the findings, the effect of the parameters are significant.}, } @article {pmid35214965, year = {2022}, author = {Khan, NA and Sulaiman, M and Tavera Romero, CA and Alshammari, FS}, title = {Analysis of Nanofluid Particles in a Duct with Thermal Radiation by Using an Efficient Metaheuristic-Driven Approach.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {4}, pages = {}, pmid = {35214965}, issn = {2079-4991}, abstract = {This study investigated the steady two-phase flow of a nanofluid in a permeable duct with thermal radiation, a magnetic field, and external forces. The basic continuity and momentum equations were considered along with the Buongiorno model to formulate the governing mathematical model of the problem. Furthermore, the intelligent computational strength of artificial neural networks (ANNs) was utilized to construct the approximate solution for the problem. The unsupervised objective functions of the governing equations in terms of mean square error were optimized by hybridizing the global search ability of an arithmetic optimization algorithm (AOA) with the local search capability of an interior point algorithm (IPA). The proposed ANN-AOA-IPA technique was implemented to study the effect of variations in the thermophoretic parameter (Nt), Hartmann number (Ha), Brownian (Nb) and radiation (Rd) motion parameters, Eckert number (Ec), Reynolds number (Re) and Schmidt number (Sc) on the velocity profile, thermal profile, Nusselt number and skin friction coefficient of the nanofluid. The results obtained by the designed metaheuristic algorithm were compared with the numerical solutions obtained by the Runge-Kutta method of order 4 (RK-4) and machine learning algorithms based on a nonlinear autoregressive network with exogenous inputs (NARX) and backpropagated Levenberg-Marquardt algorithm. The mean percentage errors in approximate solutions obtained by ANN-AOA-IPA are around 10-6 to 10-7. The graphical analysis illustrates that the velocity, temperature, and concentration profiles of the nanofluid increase with an increase in the suction parameter, Eckert number and Schmidt number, respectively. Solutions and the results of performance indicators such as mean absolute deviation, Theil's inequality coefficient and error in Nash-Sutcliffe efficiency further validate the proposed algorithm's utility and efficiency.}, } @article {pmid35214944, year = {2022}, author = {Apmann, K and Fulmer, R and Scherer, B and Good, S and Wohld, J and Vafaei, S}, title = {Nanofluid Heat Transfer: Enhancement of the Heat Transfer Coefficient inside Microchannels.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {4}, pages = {}, pmid = {35214944}, issn = {2079-4991}, abstract = {The purpose of this paper is to investigate the effects of a connector between two microchannels, for the first time. A brief literature review is provided to offer a better understanding on the impacts of concentration and the characteristics of nanoparticles on thermal conductivity, viscosity, and, consequently, the heat transfer coefficient inside the microchannels. The given literature review aims to help engineer nanofluids to enhance the heat transfer coefficient inside the microchannels. In this research, Fe3O4 nanoparticles were introduced into the base liquid to enhance the heat transfer coefficient inside the microchannels and to provide a better understanding of the impact of the connector between two microchannels. It was observed that the connector has a significant impact on enhancing the heat transfer coefficient inside the second microchannel, by increasing the level of randomness of molecules and particles prior to entering the second channel. The connector would act to refresh the memory of the fluid before entering the second channel, and as a result, the heat transfer coefficient in the second channel would start at a maximum value. Therefore, the overall heat transfer coefficient in both microchannels would increase for given conditions. The impacts of the Reynolds number and introducing nanoparticles in the base liquid on effects induced by the connector were investigated, suggesting that both factors play a significant role on the connector's impact on the heat transfer coefficient.}, } @article {pmid35209192, year = {2022}, author = {Kim, GB and Park, KH and Kim, SJ}, title = {Hemodynamics and Wall Shear Stress of Blood Vessels in Aortic Coarctation with Computational Fluid Dynamics Simulation.}, journal = {Molecules (Basel, Switzerland)}, volume = {27}, number = {4}, pages = {}, pmid = {35209192}, issn = {1420-3049}, support = {2021R1A2C1091322//National Research Foundation of Korea/ ; }, mesh = {Algorithms ; Aorta/abnormalities/diagnostic imaging/physiopathology ; Aortic Coarctation/*diagnosis/*physiopathology ; Blood Flow Velocity ; *Hemodynamics ; Humans ; *Models, Cardiovascular ; *Stress, Mechanical ; }, abstract = {The purpose of this study was to identify the characteristics of blood flow in aortic coarctation based on stenotic shape structure, stenosis rate, and the distribution of the wall load delivered into the blood vessels and to predict the impact on aneurysm formation and rupture of blood vessels by using a computational fluid dynamics modeling method. It was applied on the blood flow in abdominal aortic blood vessels in which stenosis occurred by using the commercial finite element software ADINA on fluid-solid interactions. The results of modeling, with an increasing stenosis rate and Reynolds number, showed the pressure drop was increased and the velocity was greatly changed. When the stenosis rate was the same, the pressure drop and the velocity change were larger in the stenosis with a symmetric structure than in the stenosis with an asymmetric one. Maximal changes in wall shear stress were observed in the area before stenosis and minimal changes were shown in stenosis areas. The minimal shear stress occurred at different locations depending on the stenosis shape models. With an increasing stenosis rate and Reynolds number, the maximal wall shear stress was increased and the minimal wall shear stress was decreased. Through such studies, it is thought that the characteristics of blood flow in the abdominal aorta where a stenosis is formed will be helpful in understanding the mechanism of growth of atherosclerosis and the occurrence and rupture of the abdominal aortic flow.}, } @article {pmid35208284, year = {2022}, author = {Antognoli, M and Tomasi Masoni, S and Mariotti, A and Mauri, R and Salvetti, MV and Brunazzi, E and Galletti, C}, title = {Mixing Improvement in a T-Shaped Micro-Junction through Small Rectangular Cavities.}, journal = {Micromachines}, volume = {13}, number = {2}, pages = {}, pmid = {35208284}, issn = {2072-666X}, abstract = {The T-shaped micro-junction is among the most used geometry in microfluidic applications, and many design modifications of the channel walls have been proposed to enhance mixing. In this work, we investigate through numerical simulations the introduction of one pair of small rectangular cavities in the lateral walls of the mixing channel just downstream of the confluence region. The aim is to preserve the simple geometry that has contributed to spread the practical use of the T-shaped micro-junction while suggesting a modification that should, in principle, work jointly with the vortical structures present in the mixing channel, further enhancing their efficiency in mixing without significant additional pressure drops. The performance is analyzed in the different flow regimes occurring by increasing the Reynolds number. The cavities are effective in the two highly-mixed flow regimes, viz., the steady engulfment and the periodic asymmetric regimes. This presence does not interfere with the formation of the vortical structures that promote mixing by convection in these two regimes, but it further enhances the mixing of the inlet streams in the near-wall region of the mixing channel without any additional cost, leading to better performance than the classical configuration.}, } @article {pmid35207114, year = {2022}, author = {Nichka, V and Mareev, S and Pismenskaya, N and Nikonenko, V and Bazinet, L}, title = {Mathematical Modeling of the Effect of Pulsed Electric Field Mode and Solution Flow Rate on Protein Fouling during Bipolar Membrane Electroacidificaiton of Caseinate Solution.}, journal = {Membranes}, volume = {12}, number = {2}, pages = {}, pmid = {35207114}, issn = {2077-0375}, support = {21-19-00087//Russian Science Foundation/ ; 210829409//Natural Sciences and Engineering Research Council/ ; }, abstract = {A one-dimensional non-stationary model was developed for a better understanding of the protein fouling formation mechanism during electroacidification of caseinate solution using electrodialysis with bipolar membranes (EDBM) in pulsed electric field (PEF) mode. Four different PEF modes were investigated with pulse-pause durations of 10-10 s, 10-20 s, 10-33 s, 10-50 s. For each current mode 3 different flow rates were considered, corresponding to Reynolds numbers, Re, equal to 187, 374 and 560. The processes are considered in the diffusion boundary layer between the surface of the cation-exchange layer of bipolar membrane and bulk solution of the desalination compartment. The Nernst-Planck and material balance equation systems describe the ion transport. The electroneutrality condition and equilibrium chemical reactions are taken into account. The calculation results using the developed model are in qualitative agreement with the experimental data obtained during the previous experimental part of the study. It is confirmed that both the electrical PEF mode and the flow rate have a significant effect on the thickness (and mass) of the protein fouling during EDBM. Moreover, the choice of the electric current mode has the main impact on the fouling formation rate; an increase in the PEF pause duration leads to a decrease in the amount of fouling. It was shown that an increase in the PEF pause duration from 10 s to 50 s, in combination with an increase in Reynolds number (the flow rate) from 187 to 560, makes it possible to reduce synergistically the mass of protein deposits from 6 to 1.3 mg/cm[2], which corresponds to a 78% decrease.}, } @article {pmid35205589, year = {2022}, author = {Yang, X and Yang, L}, title = {Numerical Study of Entropy Generation in Fully Developed Turbulent Circular Tube Flow Using an Elliptic Blending Turbulence Model.}, journal = {Entropy (Basel, Switzerland)}, volume = {24}, number = {2}, pages = {}, pmid = {35205589}, issn = {1099-4300}, abstract = {As computational fluid dynamics (CFD) advances, entropy generation minimization based on CFD becomes attractive for optimizing complex heat-transfer systems. This optimization depends on the accuracy of CFD results, such that accurate turbulence models, such as elliptic relaxation or elliptic blending turbulence models, become important. The performance of a previously developed elliptic blending turbulence model (the SST k-ω-φ-α model) to predict the rate of entropy generation in the fully developed turbulent circular tube flow with constant heat flux was studied to provide some guidelines for using this class of turbulence model to calculate entropy generation in complex systems. The flow and temperature fields were simulated by using a CFD package, and then the rate of entropy generation was calculated in post-processing. The analytical correlations and results of two popular turbulence models (the realizable k-ε and the shear stress transport (SST) k-ω models) were used as references to demonstrate the accuracy of the SST k-ω-φ-α model. The findings indicate that the turbulent Prandtl number (Prt) influences the entropy generation rate due to heat-transfer irreversibility. Prt = 0.85 produces the best results for the SST k-ω-φ-α model. For the realizable k-ε and SST k-ω models, Prt = 0.85 and Prt = 0.92 produce the best results, respectively. For the realizable k-ε and the SST k-ω models, the two methods used to predict the rate of entropy generation due to friction irreversibility produce the same results. However, for the SST k-ω-φ-α model, the rates of entropy generation due to friction irreversibility predicted by the two methods are different. The difference at a Reynolds number of 100,000 is about 14%. The method that incorporates the effective turbulent viscosity should be used to predict the rate of entropy generation due to friction irreversibility for the SST k-ω-φ-α model. Furthermore, when the temperature in the flow field changes dramatically, the temperature-dependent fluid properties must be considered.}, } @article {pmid35196405, year = {2022}, author = {Xia, N and Jin, B and Jin, D and Yang, Z and Pan, C and Wang, Q and Ji, F and Iacovacci, V and Majidi, C and Ding, Y and Zhang, L}, title = {Decoupling and Reprogramming the Wiggling Motion of Midge Larvae Using a Soft Robotic Platform.}, journal = {Advanced materials (Deerfield Beach, Fla.)}, volume = {34}, number = {17}, pages = {e2109126}, doi = {10.1002/adma.202109126}, pmid = {35196405}, issn = {1521-4095}, support = {JLFS/E-402/18//Hong Kong Research Grants Council/ ; MRP/036/18X//ITF/ ; //HKSAR Innovation and Technology Commission/ ; CAS20403//Croucher Foundation Grant/ ; U1930402//National Science Foundation of China/ ; }, mesh = {Animals ; Biomimetics ; Larva ; Locomotion ; *Robotics ; Swimming ; }, abstract = {The efficient motility of invertebrates helps them survive under evolutionary pressures. Reconstructing the locomotion of invertebrates and decoupling the influence of individual basic motion are crucial for understanding their underlying mechanisms, which, however, generally remain a challenge due to the complexity of locomotion gaits. Herein, a magnetic soft robot to reproduce midge larva's key natural swimming gaits is developed, and the coupling effect between body curling and rotation on motility is investigated. Through the authors' systematically decoupling studies using programmed magnetic field inputs, the soft robot (named LarvaBot) experiences various coupled gaits, including biomimetic side-to-side flexures, and unveils that the optimal rotation amplitude and the synchronization of curling and rotation greatly enhance its motility. The LarvaBot achieves fast locomotion and upstream capability at the moderate Reynolds number regime. The soft robotics-based platform provides new insight to decouple complex biological locomotion, and design programmed swimming gaits for the fast locomotion of soft-bodied swimmers.}, } @article {pmid35193246, year = {2022}, author = {Czelusniak, LE and Mapelli, VP and Wagner, AJ and Cabezas-Gómez, L}, title = {Shaping the equation of state to improve numerical accuracy and stability of the pseudopotential lattice Boltzmann method.}, journal = {Physical review. E}, volume = {105}, number = {1-2}, pages = {015303}, doi = {10.1103/PhysRevE.105.015303}, pmid = {35193246}, issn = {2470-0053}, abstract = {It has recently been shown that altering the shape of the metastable and unstable branches of an equation of state (EOS) can substantially improve the numerical accuracy of liquid and vapor densities in the pseudopotential lattice Boltzmann method [Peng et al., Phys. Rev. E 101, 063309 (2020)2470-004510.1103/PhysRevE.101.063309]. We found that this approach reduces stability of the method in nonequilibrium conditions and is unstable for bubbles at low reduced temperatures. Here we present an improved method for altering the shape of the metastable and unstable branches of the EOS which remains stable for both equilibrium and nonequilibrium situations and has no issues with bubbles. We also performed a detailed study of the stability of the methods for a droplet impact on a liquid film for reduced temperatures down to 0.35 with Reynolds number of 300. Our approach remained stable for a density ratio of up to 3.38×10^{4}.}, } @article {pmid35193206, year = {2022}, author = {Richter, SK and Menzel, AM}, title = {Mediated interactions between rigid inclusions in two-dimensional elastic or fluid films.}, journal = {Physical review. E}, volume = {105}, number = {1-1}, pages = {014609}, doi = {10.1103/PhysRevE.105.014609}, pmid = {35193206}, issn = {2470-0053}, abstract = {Interactions between rigid inclusions in continuous three-dimensional linearly elastic solids and low-Reynolds-number viscous fluids have largely been quantified in the past. Prime example systems are given by functionalized elastic composite materials or fluid colloidal suspensions. Here, we address the significantly less frequently studied situation of rigid inclusions in two-dimensional elastic or low-Reynolds-number fluid films. We concentrate on the situation in which disklike inclusions remain well separated from each other and do not get into contact. Specifically, we demonstrate and explain that the logarithmic divergence of the associated Green's function is removed in the absence of net external forces on the inclusions, in line with physical intuition. For instance, this situation applies when only pairwise mutual interactions between the inclusions prevail. Our results will support, for example, investigations on membranes functionalized by appropriate inclusions, both of technical or biological origin, or the dynamics of active microswimmers in appropriately prepared thin films.}, } @article {pmid35190663, year = {2022}, author = {Hamzah, HK and Ali, FH and Hatami, M}, title = {MHD mixed convection and entropy generation of CNT-water nanofluid in a wavy lid-driven porous enclosure at different boundary conditions.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {2881}, pmid = {35190663}, issn = {2045-2322}, abstract = {In this study, Galerkin Finite Element Method or GFEM is used for the modeling of mixed convection with the entropy generation in wavy lid-driven porous enclosure filled by the CNT-water nanofluid under the magnetic field. Two different cases of boundary conditions for hot and cold walls are considered to study the fluid flow (streamlines) and heat transfer (local and average Nusselt numbers) as well as the entropy generation parameters. Richardson (Ri), Darcy (Da), Hartmann angle (γ), Amplitude (A), Number of peaks (N), Volume fraction (φ), Heat generation factor (λ), Hartmann number (Ha) and Reynolds number (Re) are studied parameters in this study which results indicated that at low Richardson numbers (< 1) increasing the inclined angle of magnetic field, decreases the Nu numbers, but at larger Richardson numbers (> 1) it improves the Nu numbers.}, } @article {pmid35184017, year = {2022}, author = {Bakos, V and Gyarmati, B and Csizmadia, P and Till, S and Vachoud, L and Nagy Göde, P and Tardy, GM and Szilágyi, A and Jobbágy, A and Wisniewski, C}, title = {Viscous and filamentous bulking in activated sludge: Rheological and hydrodynamic modelling based on experimental data.}, journal = {Water research}, volume = {214}, number = {}, pages = {118155}, doi = {10.1016/j.watres.2022.118155}, pmid = {35184017}, issn = {1879-2448}, abstract = {Although achieving good activated sludge settleability is a key requirement for meeting effluent quality criteria, wastewater treatment plants often face undesired floc structure changes. Filamentous bulking has widely been studied, however, viscous sludge formation much less investigated so far. Our main goal was to find relationship between sludge floc structure and related rheological properties, moreover, to estimate pressure loss in pipe networks through hydrodynamic modelling of the non-Newtonian flows in case of well settling (ideal-like), viscous and filamentous sludge. Severe viscous and filamentous kinds of bulking were generated separately in continuous-flow lab-scale systems initially seeded with the same reference (ideal-like) biomass and the entire evolution of viscous and filamentous bulking was monitored. The results suggested correlation between the rheological properties and the floc structure transformations, and showed the most appropriate fit for the Herschel-Bulkley model (vs. Power-law and Bingham). Validated computational fluid dynamics studies estimated the pipe pressure loss in a wide Reynolds number range for the initial well settling (reference) and the final viscous and filamentous sludge as well. A practical standard modelling protocol was developed for improving energy efficiency of sludge pumping in different floc structure scenarios.}, } @article {pmid35183949, year = {2022}, author = {Yu, Z and Yang, G and Zhang, W}, title = {A new model for the terminal settling velocity of microplastics.}, journal = {Marine pollution bulletin}, volume = {176}, number = {}, pages = {113449}, doi = {10.1016/j.marpolbul.2022.113449}, pmid = {35183949}, issn = {1879-3363}, mesh = {Environmental Monitoring ; *Microplastics ; Plastics ; *Water Pollutants, Chemical/analysis ; }, abstract = {Microplastic (MP) settling process is important for the transport of microplastic particles (MPs, <5 mm) in water bodies. However, for the control parameter of the drag coefficient (Cd), no generalized formula has been proposed for MPs of different shapes and materials. In this study, a total of 1343 MP settling data were collected from the literature. It was found that the drag law for perfect spheres cannot reasonably predict Cd for MPs with particle Reynolds number of 1-10[3]. A new formula for Cd was developed by introducing the dimensionless particle diameter (d⁎) and two shape descriptors. The absolute error of the new formula is 15.2%, smaller than those (42.5-72.8%) of other existing formulas. Moreover, an explicit model was developed for MP settling velocity by correlating Cd, d⁎, and shape descriptors, with lower absolute error (8.8%) than those (15.4-77.2%) of existing models.}, } @article {pmid35160419, year = {2022}, author = {Faroughi, SA and Roriz, AI and Fernandes, C}, title = {A Meta-Model to Predict the Drag Coefficient of a Particle Translating in Viscoelastic Fluids: A Machine Learning Approach.}, journal = {Polymers}, volume = {14}, number = {3}, pages = {}, pmid = {35160419}, issn = {2073-4360}, support = {UID-B/05256/2020, UID-P/05256/2020, MIT-EXPL/TDI/0038/2019//FEDER funds through the COMPETE 2020 Programme and National Funds through FCT (Portuguese Foundation for Science and Technology)/ ; NORTE-07-0162-FEDER-000086//University of Minho cluster/ ; CPCA A2 6052 2020//Minho Advanced Computing Center/ ; HPC-EUROPA3 (INFRAIA-2016-1-730897)//Consorzio Interuniversitario dell'Italia Nord Est per il Calcolo Automatico (CINECA)/ ; icei-prace-2020-0009//PRACE - Partnership for Advanced Computing in Europe/ ; }, abstract = {This study presents a framework based on Machine Learning (ML) models to predict the drag coefficient of a spherical particle translating in viscoelastic fluids. For the purpose of training and testing the ML models, two datasets were generated using direct numerical simulations (DNSs) for the viscoelastic unbounded flow of Oldroyd-B (OB-set containing 12,120 data points) and Giesekus (GI-set containing 4950 data points) fluids past a spherical particle. The kinematic input features were selected to be Reynolds number, 0

METHODS: Computational Fluid Dynamics (CFD) approach is used to simulate the airflow in a neonate, an infant and an adult in sedentary breathing conditions. The healthy CT scans are segmented using MIMICS 21.0 (Materialise, Ann arbor, MI). The patient-specific 3D airway models are analyzed for low Reynolds number flow using ANSYS FLUENT 2020 R2. The applicability of the Grid Convergence Index (GCI) for polyhedral mesh adopted in this work is also verified.

RESULTS: This study shows that the inferior meatus of neonates accounted for only 15% of the total airflow. This was in contrast to the infants and adults who experienced 49 and 31% of airflow at the inferior meatus region. Superior meatus experienced 25% of total flow which is more than normal for the neonate. The highest velocity of 1.8, 2.6 and 3.7 m/s was observed at the nasal valve region for neonates, infants and adults, respectively. The anterior portion of the nasal cavity experienced maximum wall shear stress with average values of 0.48, 0.25 and 0.58 Pa for the neonates, infants and adults.

CONCLUSIONS: The neonates have an underdeveloped nasal cavity which significantly affects their airway distribution. The absence of inferior meatus in the neonates has limited the flow through the inferior regions and resulted in uneven flow distribution.}, } @article {pmid34846896, year = {2021}, author = {Kim, AR and Mitra, SK and Zhao, B}, title = {Reduced Pressure Drop in Viscoelastic Polydimethylsiloxane Wall Channels.}, journal = {Langmuir : the ACS journal of surfaces and colloids}, volume = {37}, number = {49}, pages = {14292-14301}, doi = {10.1021/acs.langmuir.1c02087}, pmid = {34846896}, issn = {1520-5827}, mesh = {Biological Transport ; *Dimethylpolysiloxanes ; *Lab-On-A-Chip Devices ; Viscosity ; }, abstract = {Polydimethylsiloxane (PDMS) is an important viscoelastic material that finds applications in a large number of engineering systems, particularly lab-on-chip microfluidic devices built with a flexible substrate. Channels made of PDMS, used for transporting analytes, are integral to these applications. The PDMS viscoelastic nature can induce additional hydrodynamic contributions at the soft wall/fluid interface compared to rigid walls. In this research, we investigated the pressure drop within PDMS channels bounded by rigid tubes (cellulose tubes). The bulging effect of the PDMS was limited by the rigid tubes under flowing fluids. The PDMS viscoelasticity was modulated by changing the ratio of the base to the cross-linker from 10:1 to 35:1. We observed that the pressure drop of the flowing fluids within the channel decreased with the increased loss tangent of the PDMS in the examined laminar regime [Reynolds number (Re) ∼ 23-58.6 for water and Re ∼ 0.69-8.69 for glycerol solution]. The elastic PDMS 10:1 wall channels followed the classical Hagen Poiseuille's equation, but the PDMS walls with lower cross-linker concentrations and thicker walls decreased pressure drops. The friction factor (f) for the PDMS channels with the two working fluids could be approximated as f = 47/Re. We provide a correlation between the pressure drop and PDMS viscoelasticity based on experimental findings. In the correlation, the loss tangent predominates; the larger the loss tangent, the smaller is the pressure drop. The research findings appear to be unexpected if only considering the energy dissipation of viscoelastic PDMS walls. We attributed the reduction in the pressure drop to a lubricating effect of the viscoelastic PDMS walls in the presence of the working fluids. Our results reveal the importance of the subtle diffusion of the residual oligomers and water from the bulk to the soft wall/fluid interface for the observed pressure drop in soft wall channels.}, } @article {pmid34846030, year = {2021}, author = {Chen, X and Zhan, Y and Fu, YI and Lin, J and Ji, Y and Zhao, C and Fang, Y and Wu, J}, title = {The effect of stenosis rate and Reynolds number on local flow characteristics and plaque formation around the atherosclerotic stenosis.}, journal = {Acta of bioengineering and biomechanics}, volume = {23}, number = {1}, pages = {135-147}, pmid = {34846030}, issn = {1509-409X}, mesh = {*Atherosclerosis ; Constriction, Pathologic ; Hemodynamics ; Humans ; *Models, Cardiovascular ; Stress, Mechanical ; }, abstract = {PURPOSE: Atherosclerosis causes plaque to build-up in arteries. Effect of the specific local hemodynamic environment around an atherosclerotic plaque on the thrombosis formation does not remain quite clear but is believed to be crucial. The aim of this study is to uncover the flow effects on plaques formation.

METHODS: To study the mechanically regulated plaque formation, the flow fields in artery blood vessels with different stenosis rates at various Reynolds numbers were simulated numerically with the two-dimensional axisymmetric models, and the hemodynamic characteristics around the plaque were scaled with stenosis rate and Reynolds number.

RESULTS: The results showed that increases of both Reynolds number and stenosis rate facilitated the occurrence of flow separation phenomenon, extended recirculation zone, and upregulated the maximum normalized wall shear stress near the plaque throat section while downregulated the minimal normalized wall shear stress at the front shoulder of plaque, as it should be; in the atherosclerotic plaque leeside of the recirculation zone, an obvious catch bond region of wall shear stress might exist especially under low Reynolds number with stenosis rate smaller than 30%. This catch bond region in the plaque leeside might be responsible for the LBF (low blood flow)-enhanced formation of the atherosclerotic plaque.

CONCLUSIONS: This work may provide a novel insight into understanding the biomechanical effects behind the formation and damage of atherosclerotic plaques and propose a new strategy for preventing atherosclerotic diseases.}, } @article {pmid34845537, year = {2021}, author = {Patel, K and Stark, H}, title = {Instability of a liquid sheet with viscosity contrast in inertial microfluidics.}, journal = {The European physical journal. E, Soft matter}, volume = {44}, number = {11}, pages = {144}, pmid = {34845537}, issn = {1292-895X}, abstract = {Flows at moderate Reynolds numbers in inertial microfluidics enable high throughput and inertial focusing of particles and cells with relevance in biomedical applications. In the present work, we consider a viscosity-stratified three-layer flow in the inertial regime. We investigate the interfacial instability of a liquid sheet surrounded by a density-matched but more viscous fluid in a channel flow. We use linear stability analysis based on the Orr-Sommerfeld equation and direct numerical simulations with the lattice Boltzmann method (LBM) to perform an extensive parameter study. Our aim is to contribute to a controlled droplet production in inertial microfluidics. In the first part, on the linear stability analysis we show that the growth rate of the fastest growing mode [Formula: see text] increases with the Reynolds number [Formula: see text] and that its wavelength [Formula: see text] is always smaller than the channel width w for sufficiently small interfacial tension [Formula: see text]. For thin sheets we find the scaling relation [Formula: see text], where m is viscosity ratio and [Formula: see text] the sheet thickness. In contrast, for thicker sheets [Formula: see text] decreases with increasing [Formula: see text] or m due to the nearby channel walls. Examining the eigenvalue spectra, we identify Yih modes at the interface. In the second part on the LBM simulations, the thin liquid sheet develops two distinct dynamic states: waves traveling along the interface and breakup into droplets with bullet shape. For smaller flow rates and larger sheet thicknesses, we also observe ligament formation and the sheet eventually evolves irregularly. Our work gives some indication how droplet formation can be controlled with a suitable parameter set [Formula: see text].}, } @article {pmid34845318, year = {2021}, author = {Pang, M and Zhang, T and Meng, Y and Ling, Z}, title = {Experimental study on the permeability of crushed coal medium based on the Ergun equation.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {23030}, pmid = {34845318}, issn = {2045-2322}, support = {51774234//the National Natural Science Foundations of China/ ; }, abstract = {Accurate determination of the permeability of crushed coal medium is the basis for the study of their permeability characteristics. To investigate the permeability characteristics of this special porous medium composed of crushed coal particles, the permeability parameters of crushed coal specimens of different initial porosities were measured by designing a lateral-limit compression seepage test system. Parameters were determined separately for specimens of different initial porosities. (1) the Reynolds number distribution region characterising the seepage state was determined and obtained. Specimens with initial porosity distribution between 0.02 and 0.08, and seepage Reynolds number distribution in the low-permeability zone, under Darcy flow; (2) the intrinsic permeability of the crushed coal medium was obtained by using the Ergun equation. The complex inverse proportional relationship between the drag coefficient and Reynolds number was derived; (3) Through the determination of the permeability of the crushed coal medium, the mean value of βK value was obtained to be about 45.7, and the analysis of the permeability of porous medium can determine its critical permeability. The relationship between the Forchheimer number Fo and critical Reynolds number was measured. The results indicate that it conforms to a linear distribution. In-depth analysis of these two parameters can be used to explore the flow transition process between laminar, transition, and turbulent flow. This study provides insight into the permeability characteristics of the media in fractured coal bodies.}, } @article {pmid34840965, year = {2021}, author = {Krane, M}, title = {Vortex Formation Times in the Glottal Jet, Measured in a Scaled-Up Model.}, journal = {Fluids (Basel, Switzerland)}, volume = {6}, number = {11}, pages = {}, pmid = {34840965}, issn = {2311-5521}, support = {R01 DC005642/DC/NIDCD NIH HHS/United States ; }, abstract = {In this paper, the timing of vortex formation on the glottal jet is studied using previously published velocity measurements of flow through a scaled-up model of the human vocal folds. The relative timing of the pulsatile glottal jet and the instability vortices are acoustically important since they determine the harmonic and broadband content of the voice signal. Glottis exit jet velocity time series were extracted from time-resolved planar DPIV measurements. These measurements were acquired at four glottal flow speeds (u SS = 16.1-38 cm/s) and four glottis open times (T o = 5.67-23.7 s), providing a Reynolds number range Re = 4100-9700 and reduced vibration frequency f* = 0.01-0.06. Exit velocity waveforms showed temporal behavior on two time scales, one that correlates to the period of vibration and another characterized by short, sharp velocity peaks (which correlate to the passage of instability vortices through the glottis exit plane). The vortex formation time, estimated by computing the time difference between subsequent peaks, was shown to be not well-correlated from one vibration cycle to the next. The principal finding is that vortex formation time depends not only on cycle phase, but varies strongly with reduced frequency of vibration. In all cases, a strong high-frequency burst of vortex motion occurs near the end of the cycle, consistent with perceptual studies using synthesized speech.}, } @article {pmid34832781, year = {2021}, author = {Jbeili, M and Zhang, J}, title = {Effects of Microscopic Properties on Macroscopic Thermal Conductivity for Convective Heat Transfer in Porous Materials.}, journal = {Micromachines}, volume = {12}, number = {11}, pages = {}, pmid = {34832781}, issn = {2072-666X}, support = {Discovery Grant - Individual//Natural Sciences and Engineering Research Council/ ; }, abstract = {Porous materials are widely used in many heat transfer applications. Modeling porous materials at the microscopic level can accurately incorporate the detailed structure and substance parameters and thus provides valuable information for the complex heat transfer processes in such media. In this study, we use the generalized periodic boundary condition for pore-scale simulations of thermal flows in porous materials. A two-dimensional porous model consisting of circular solid domains is considered, and comprehensive simulations are performed to study the influences on macroscopic thermal conductivity from several microscopic system parameters, including the porosity, Reynolds number, and periodic unit aspect ratio and the thermal conductance at the solid-fluid interface. Our results show that, even at the same porosity and Reynolds number, the aspect ratio of the periodic unit and the interfacial thermal conductance can significantly affect the macroscopic thermal behaviors of porous materials. Qualitative analysis is also provided to relate the apparent thermal conductivity to the complex flow and temperature distributions in the microscopic porous structure. The method, findings and discussions presented in this paper could be useful for fundamental studies, material development, and engineering applications of porous thermal flow systems.}, } @article {pmid34828226, year = {2021}, author = {Li, W and Xie, Z and Xi, K and Xia, S and Ge, Y}, title = {Constructal Optimization of Rectangular Microchannel Heat Sink with Porous Medium for Entropy Generation Minimization.}, journal = {Entropy (Basel, Switzerland)}, volume = {23}, number = {11}, pages = {}, pmid = {34828226}, issn = {1099-4300}, support = {51979278//National Natural Science Foundation of China/ ; 51579244//National Natural Science Foundation of China/ ; }, abstract = {A model of rectangular microchannel heat sink (MCHS) with porous medium (PM) is developed. Aspect ratio of heat sink (HS) cell and length-width ratio of HS are optimized by numerical simulation method for entropy generation minimization (EGM) according to constructal theory. The effects of inlet Reynolds number (Re) of coolant, heat flux on bottom, porosity and volume proportion of PM on dimensionless entropy generation rate (DEGR) are analyzed. From the results, there are optimal aspect ratios to minimize DEGR. Given the initial condition, DEGR is 33.10% lower than its initial value after the aspect ratio is optimized. With the increase of Re, the optimal aspect ratio declines, and the minimum DEGR drops as well. DEGR gets larger and the optimal aspect ratio remains constant with the increasing of heat flux on bottom. For the different volume proportion of PM, the optimal aspect ratios are diverse, but the minimum DEGR almost stays unchanged. The twice minimized DEGR, which results from aspect ratio and length-width ratio optimized simultaneously, is 10.70% lower than the once minimized DEGR. For a rectangular bottom, a lower DEGR can be reached by choosing the proper direction of fluid flow.}, } @article {pmid34828211, year = {2021}, author = {Khan, MF and Sulaiman, M and Tavera Romero, CA and Alkhathlan, A}, title = {A Hybrid Metaheuristic Based on Neurocomputing for Analysis of Unipolar Electrohydrodynamic Pump Flow.}, journal = {Entropy (Basel, Switzerland)}, volume = {23}, number = {11}, pages = {}, pmid = {34828211}, issn = {1099-4300}, abstract = {A unipolar electrohydrodynamic (UP-EHD) pump flow is studied with known electric potential at the emitter and zero electric potential at the collector. The model is designed for electric potential, charge density, and electric field. The dimensionless parameters, namely the electrical source number (Es), the electrical Reynolds number (ReE), and electrical slip number (Esl), are considered with wide ranges of variation to analyze the UP-EHD pump flow. To interpret the pump flow of the UP-EHD model, a hybrid metaheuristic solver is designed, consisting of the recently developed technique sine-cosine algorithm (SCA) and sequential quadratic programming (SQP) under the influence of an artificial neural network. The method is abbreviated as ANN-SCA-SQP. The superiority of the technique is shown by comparing the solution with reference solutions. For a large data set, the technique is executed for one hundred independent experiments. The performance is evaluated through performance operators and convergence plots.}, } @article {pmid34828180, year = {2021}, author = {Jia, Y and Huang, J and Wang, J and Li, H}, title = {Heat Transfer and Fluid Flow Characteristics of Microchannel with Oval-Shaped Micro Pin Fins.}, journal = {Entropy (Basel, Switzerland)}, volume = {23}, number = {11}, pages = {}, pmid = {34828180}, issn = {1099-4300}, support = {5210060458//National Natural Science Foundation of China/ ; JJKH20210112KJ//The Scientific research project of Jilin Provincial Department of Education/ ; }, abstract = {A novel microchannel heat sink with oval-shaped micro pin fins (MOPF) is proposed and the characteristics of fluid flow and heat transfer are studied numerically for Reynolds number (Re) ranging from 157 to 668. In order to study the influence of geometry on flow and heat transfer characteristics, three non-dimensional variables are defined, such as the fin axial length ratio (α), width ratio (β), and height ratio (γ). The thermal enhancement factor (η) is adopted as an evaluation criterion to evaluate the best comprehensive thermal-hydraulic performance of MOPF. Results indicate that the oval-shaped pin fins in the microchannel can effectively prevent the rise of heat surface temperature along the flow direction, which improves the temperature distribution uniformity. In addition, results show that for the studied Reynolds number range and microchannel geometries in this paper, the thermal enhancement factor η increases firstly and then decreases with the increase of α and β. In addition, except for Re = 157, η decreases first and then increases with the increase of the fin height ratio γ. The thermal enhancement factor for MOPF with α = 4, β = 0.3, and γ = 0.5 achieves 1.56 at Re = 668. The results can provide a theoretical basis for the design of a microchannel heat exchanger.}, } @article {pmid34818642, year = {2021}, author = {Hernández Meza, JM and Vélez-Cordero, JR and Ramírez Saito, A and Aranda-Espinoza, S and Arauz-Lara, JL and Yáñez Soto, B}, title = {Particle/wall electroviscous effects at the micron scale: comparison between experiments, analytical and numerical models.}, journal = {Journal of physics. Condensed matter : an Institute of Physics journal}, volume = {34}, number = {9}, pages = {}, doi = {10.1088/1361-648X/ac3cef}, pmid = {34818642}, issn = {1361-648X}, abstract = {We report a experimental study of the motion of 1 μm single particles interacting with functionalized walls at low and moderate ionic strengths conditions. The 3D particle's trajectories were obtained by analyzing the diffracted particle images (point spread function). The studied particle/wall systems include negatively charged particles interacting with bare glass, glass covered with polyelectrolytes and glass covered with a lipid monolayer. In the low salt regime (pure water) we observed a retardation effect of the short-time diffusion coefficients when the particle interacts with a negatively charged wall; this effect is more severe in the perpendicular than in the lateral component. The decrease of the diffusion as a function of the particle-wall distancehwas similar regardless the origin of the negative charge at the wall. When surface charge was screened or salt was added to the medium (10 mM), the diffusivity curves recover the classical hydrodynamic behavior. Electroviscous theory based on the thin electrical double layer (EDL) approximation reproduces the experimental data except for smallh. On the other hand, 2D numerical solutions of the electrokinetic equations showed good qualitative agreement with experiments. The numerical model also showed that the hydrodynamic and Maxwellian part of the electroviscous total drag tend to zero ash→ 0 and how this is linked with the merging of both EDL's at close proximity.}, } @article {pmid34816334, year = {2021}, author = {Díaz, MV}, title = {On the long-time persistence of hydrodynamic memory.}, journal = {The European physical journal. E, Soft matter}, volume = {44}, number = {11}, pages = {141}, pmid = {34816334}, issn = {1292-895X}, abstract = {The Basset-Boussinesq-Oseen (BBO) equation correctly describes the nonuniform motion of a spherical particle at a low Reynolds number. It contains an integral term with a singular kernel which accounts for the diffusion of vorticity around the particle throughout its entire history. However, if there are any departures in either rigidity or shape from a solid sphere, besides the integral force with a singular kernel, the Basset history force, we should add a second history force with a non-singular kernel, related to the shape or composition of the particle. In this work, we introduce a fractional generalized Basset-Boussinesq-Oseen equation which includes both history terms as fractional derivatives. Using the Laplace transform, an integral representation of the solution is obtained. For a driven single particle, the solution shows that memory effects persist indefinitely under rather general driving conditions.}, } @article {pmid34805706, year = {2021}, author = {Yin, B and Yue, W and Sohan, ASMMF and Zhou, T and Qian, C and Wan, X}, title = {Micromixer with Fine-Tuned Mathematical Spiral Structures.}, journal = {ACS omega}, volume = {6}, number = {45}, pages = {30779-30789}, pmid = {34805706}, issn = {2470-1343}, abstract = {Micromixers with the microchannel structure can enable rapid and efficient mixing of multiple types of fluids on a microfluidic chip. Herein, we report the mixing performance of three passive micromixers based on the different mathematical spiral structures. We study the fluid flow characteristics of Archimedes spiral, Fermat spiral, and hyperbolic spiral structures with various channel widths and Reynolds number (Re) ranging from 0 to 10 via numerical simulation and visualization experiments. In addition, we analyze the mechanism of streamlines and Dean vortices at different cross sections during fluid flows. As the fluid flows in the Fermat spiral channel, the centrifugal force induces the Dean vortex to form a chaotic advection, enhancing the fluid mixing performance. By integrating the Fermat spiral channel into a microfluidic chip, we successfully detect acute myocardial infarction (AMI) marker with the double-antibody sandwich method and reduce the detection time to 10 min. This method has a low reagent consumption and a high reaction efficiency and demonstrates great potential in point-of-care testing (POCT).}, } @article {pmid34797128, year = {2021}, author = {Jaccod, A and Chibbaro, S}, title = {Constrained Reversible System for Navier-Stokes Turbulence.}, journal = {Physical review letters}, volume = {127}, number = {19}, pages = {194501}, doi = {10.1103/PhysRevLett.127.194501}, pmid = {34797128}, issn = {1079-7114}, abstract = {Following a Gallavotti's conjecture, stationary states of Navier-Stokes fluids are proposed to be described equivalently by alternative equations besides the Navier-Stokes equation itself. We discuss a model system symmetric under time reversal based on the Navier-Stokes equations constrained to keep the enstrophy constant. It is demonstrated through highly resolved numerical experiments that the reversible model evolves to a stationary state which reproduces quite accurately all statistical observables relevant for the physics of turbulence extracted by direct numerical simulations (DNS) at different Reynolds numbers. The possibility of using reversible models to mimic turbulence dynamics is of practical importance for the coarse-grained version of Navier-Stokes equations, as used in large-eddy simulations. Furthermore, the reversible model appears mathematically simpler, since enstrophy is bounded to be constant for every Reynolds number. Finally, the theoretical interest in the context of statistical mechanics is briefly discussed.}, } @article {pmid34781498, year = {2021}, author = {An, X and Dong, B and Wang, Y and Zhang, Y and Zhou, X and Li, W}, title = {Coupled lattice Boltzmann-large eddy simulation model for three-dimensional multiphase flows at large density ratio and high Reynolds number.}, journal = {Physical review. E}, volume = {104}, number = {4-2}, pages = {045305}, doi = {10.1103/PhysRevE.104.045305}, pmid = {34781498}, issn = {2470-0053}, abstract = {A coupled lattice Boltzmann-large eddy simulation model is developed for modeling three-dimensional multiphase flows at large density ratios and high Reynolds numbers. In the framework of the lattice Boltzmann method, the model is proposed based on the standard Smagorinsky subgrid-scale approach, and a reconstructed multiple-relaxation-time collision operator is adopted. The conservative Allen-Cahn equation and Navier-Stokes equations are solved through the lattice Boltzmann discretization scheme for the interface tracking and velocity field evolution, respectively. Relevant benchmark cases are carried out to validate the performance of this model in simulating multiphase flows at a large density ratio and a high Reynolds number, including a stationary droplet, the process of spinodal decomposition, the Rayleigh-Taylor instability, the phenomenon of a droplet splashing on a thin liquid film, and the liquid jet breakup process. The maximum values of density ratio and Re number are 1000 and 10 240, respectively. The capability and reliability of the proposed model have been demonstrated by the good agreement between simulation results and the analytical solutions or the previously available results.}, } @article {pmid34776531, year = {2021}, author = {Braun, S and Scheichl, S and Kuzdas, D}, title = {The triple-deck stage of marginal separation.}, journal = {Journal of engineering mathematics}, volume = {128}, number = {1}, pages = {16}, pmid = {34776531}, issn = {0022-0833}, abstract = {UNLABELLED: The method of matched asymptotic expansions is applied to the investigation of transitional separation bubbles. The problem-specific Reynolds number is assumed to be large and acts as the primary perturbation parameter. Four subsequent stages can be identified as playing key roles in the characterization of the incipient laminar-turbulent transition process: due to the action of an adverse pressure gradient, a classical laminar boundary layer is forced to separate marginally (I). Taking into account viscous-inviscid interaction then enables the description of localized, predominantly steady, reverse flow regions (II). However, certain conditions (e.g. imposed perturbations) may lead to a finite-time breakdown of the underlying reduced set of equations. The ensuing consideration of even shorter spatio-temporal scales results in the flow being governed by another triple-deck interaction. This model is capable of both resolving the finite-time singularity and reproducing the spike formation (III) that, as known from experimental observations and direct numerical simulations, sets in prior to vortex shedding at the rear of the bubble. Usually, the triple-deck stage again terminates in the form of a finite-time blow-up. The study of this event gives rise to a noninteracting Euler-Prandtl stage (IV) associated with unsteady separation, where the vortex wind-up and shedding process takes place. The focus of the present paper lies on the triple-deck stage III and is twofold: firstly, a comprehensive numerical investigation based on a Chebyshev collocation method is presented. Secondly, a composite asymptotic model for the regularization of the ill-posed Cauchy problem is developed.

SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10665-021-10125-3.}, } @article {pmid34766181, year = {2022}, author = {Yu, P and Durgesh, V}, title = {Application of Dynamic Mode Decomposition to Study Temporal Flow Behavior in a Saccular Aneurysm.}, journal = {Journal of biomechanical engineering}, volume = {144}, number = {5}, pages = {}, doi = {10.1115/1.4052999}, pmid = {34766181}, issn = {1528-8951}, mesh = {Blood Flow Velocity ; Hemodynamics ; Humans ; *Intracranial Aneurysm ; Models, Cardiovascular ; Rheology ; }, abstract = {Aneurysms are abnormal expansion of weakened blood vessels which can cause mortality or long-term disability upon rupture. Several studies have shown that inflow conditions spatially and temporally influence aneurysm flow behavior. The objective of this investigation is to identify impact of inflow conditions on spatio-temporal flow behavior in an aneurysm using dynamic mode decomposition (DMD). For this purpose, low-frame rate velocity field measurements are performed in an idealized aneurysm model using particle image velocimetry (PIV). The inflow conditions are precisely controlled using a ViVitro SuperPump system where nondimensional fluid parameters such as peak Reynolds number (Rep) and Womersely number (α) are varied from 50-270 and 2-5, respectively. The results show the ability of DMD to identify the spatial flow structures and their frequency content. Furthermore, DMD captured the impact of inflow conditions, and change in mode shapes, amplitudes, frequency, and growth rate information is observed. The DMD low-order flow reconstruction also showed the complex interplay of flow features for each inflow scenario. Furthermore, the low-order reconstruction results provided a mathematical description of the flow behavior in the aneurysm which captured the vortex formation, evolution, and convection in detail. These results indicated that the vortical structure behavior varied with the change in α while its strength and presence of secondary structures are influenced by the change in Rep.}, } @article {pmid34756978, year = {2022}, author = {Hu, F and Zhang, S and Wang, X and Wang, C and Wu, J and Poncin, S and Xu, L and Xu, G and Hu, Y and Li, HZ}, title = {Quantitative hydrodynamic characterization of high solid anaerobic digestion: Correlation of "mixing-fluidity-energy" and scale-up effect.}, journal = {Bioresource technology}, volume = {344}, number = {Pt B}, pages = {126237}, doi = {10.1016/j.biortech.2021.126237}, pmid = {34756978}, issn = {1873-2976}, mesh = {Anaerobiosis ; *Bioreactors ; *Hydrodynamics ; Rheology ; }, abstract = {High solid anaerobic digestion (HSAD)'s complex rheological behavior exhibits short-circuiting and dead zone. Mixing optimization is potential to enhance HSAD hydrodynamics. Besides, scale-up effect is quite essential for HSAD's applications, but remains rarely studied yet. Effect of impeller with different width on the correlation of "mixing-fluidity-energy" at different rotating speeds was first investigated at pilot-scale in present work. Then, scale-up effect based on rotating speed and a generalized Reynolds number was revealed from the aspects of fluidity and energy consumption. Results show that impeller width of 100 mm (10 rpm), 200 mm and 300 mm (5 and 10 rpm) are preferred for hydrodynamics and energy economics. Furthermore, Re similarity has better referential significance for the scale-up. In this study, new insight is gained into the correlation of "mixing-fluidity-energy" within a pilot-scale digester. Scale-up effect based Re similarity could potentially offer guidance for HSAD's application in the practical engineering.}, } @article {pmid34746583, year = {2021}, author = {Lian, SJ and Hu, ZX and Lan, Z and Wen, RF and Ma, XH}, title = {Optimal Operation of an Oscillatory Flow Crystallizer: Coupling Disturbance and Stability.}, journal = {ACS omega}, volume = {6}, number = {43}, pages = {28912-28922}, pmid = {34746583}, issn = {2470-1343}, abstract = {In the process of industrial crystallization, it is always difficult to balance the secondary nucleation rate and metastable zone width (MSZW). Herein, we report an experimental and numerical study for the cooling crystallization of paracetamol in an oscillatory flow crystallizer (OFC), finding the optimal operating conditions for balancing the secondary nucleation rate and MSZW. The results show that the MSZW decreases with the increase of oscillation Reynolds number (Re o). Compared to the traditional stirring system, the OFC has an MSZW three times larger than that of the stirring system under a similar power density of consumption. With the numerical simulation, the OFC can produce a stable space environment and instantaneous strong disturbance, which is conducive to the crystallization process. Above all, a high Re o is favorable to produce a sufficient nucleation rate, which may inevitably constrict the MSZW to a certain degree. Then, the optimization strategy of the operating parameter (Re o) in the OFC is proposed.}, } @article {pmid34739321, year = {2021}, author = {Browne, CA and Datta, SS}, title = {Elastic turbulence generates anomalous flow resistance in porous media.}, journal = {Science advances}, volume = {7}, number = {45}, pages = {eabj2619}, pmid = {34739321}, issn = {2375-2548}, abstract = {Many energy, environmental, industrial, and microfluidic processes rely on the flow of polymer solutions through porous media. Unexpectedly, the macroscopic flow resistance often increases above a threshold flow rate in a porous medium, but not in bulk solution. The reason why has been a puzzle for over half a century. Here, by directly visualizing flow in a transparent 3D porous medium, we demonstrate that this anomalous increase is due to the onset of an elastic instability in which the flow exhibits strong spatiotemporal fluctuations reminiscent of inertial turbulence, despite the small Reynolds number. Our measurements enable us to quantitatively establish that the energy dissipated by pore-scale fluctuations generates the anomalous increase in the overall flow resistance. Because the macroscopic resistance is one of the most fundamental descriptors of fluid flow, our results both help deepen understanding of complex fluid flows and provide guidelines to inform a broad range of applications.}, } @article {pmid34739267, year = {2021}, author = {Bott, AFA and Chen, L and Boutoux, G and Caillaud, T and Duval, A and Koenig, M and Khiar, B and Lantuéjoul, I and Le-Deroff, L and Reville, B and Rosch, R and Ryu, D and Spindloe, C and Vauzour, B and Villette, B and Schekochihin, AA and Lamb, DQ and Tzeferacos, P and Gregori, G and Casner, A}, title = {Inefficient Magnetic-Field Amplification in Supersonic Laser-Plasma Turbulence.}, journal = {Physical review letters}, volume = {127}, number = {17}, pages = {175002}, doi = {10.1103/PhysRevLett.127.175002}, pmid = {34739267}, issn = {1079-7114}, abstract = {We report a laser-plasma experiment that was carried out at the LMJ-PETAL facility and realized the first magnetized, turbulent, supersonic (Ma_{turb}≈2.5) plasma with a large magnetic Reynolds number (Rm≈45) in the laboratory. Initial seed magnetic fields were amplified, but only moderately so, and did not become dynamically significant. A notable absence of magnetic energy at scales smaller than the outer scale of the turbulent cascade was also observed. Our results support the notion that moderately supersonic, low-magnetic-Prandtl-number plasma turbulence is inefficient at amplifying magnetic fields compared to its subsonic, incompressible counterpart.}, } @article {pmid34737529, year = {2021}, author = {Behera, S and Bhardwaj, R and Agrawal, A}, title = {Effect of co-flow on fluid dynamics of a cough jet with implications in spread of COVID-19.}, journal = {Physics of fluids (Woodbury, N.Y. : 1994)}, volume = {33}, number = {10}, pages = {101701}, pmid = {34737529}, issn = {1070-6631}, abstract = {We discuss the temporal evolution of a cough jet of an infected subject in the context of the spread of COVID-19. Computations were carried out using large eddy simulation, and, in particular, the effect of the co-flow (5% and 10% of maximum cough velocity) on the evolution of the jet was quantified. The Reynolds number (Re) of the cough jet, based on the mouth opening diameter (D) and the average cough velocity, is 13 002. The time-varying inlet velocity profile of the cough jet is represented as a combination of gamma-probability-distribution functions. Simulations reveal the detailed structure of cough jet with and without a co-flow for the first time, to the best of our knowledge. The cough jet temporal evolution is similar to that of a continuous free-jet and follows the same routes of instability, as documented for a free-jet. The convection velocity of the cough jet decays with time and distance, following a power-law variation. The cough jet is observed to travel a distance of approximately 1.1 m in half a second. However, in the presence of 10% co-flow, the cough jet travels faster and covers the similar distance in just 0.33 s. Therefore, in the presence of a co-flow, the probability of transmission of COVID-19 by airborne droplets and droplet nuclei increases, since they can travel a larger distance. The cough jet without the co-flow corresponds to a larger volume content compared to that with the co-flow and spreads more within the same range of distance. These simulations are significant as they help to reveal the intricate structure of the cough jet and show that the presence of a co-flow can significantly augment the risk of infection of COVID-19.}, } @article {pmid34732570, year = {2021}, author = {Choueiri, GH and Lopez, JM and Varshney, A and Sankar, S and Hof, B}, title = {Experimental observation of the origin and structure of elastoinertial turbulence.}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {118}, number = {45}, pages = {}, pmid = {34732570}, issn = {1091-6490}, abstract = {Turbulence generally arises in shear flows if velocities and hence, inertial forces are sufficiently large. In striking contrast, viscoelastic fluids can exhibit disordered motion even at vanishing inertia. Intermediate between these cases, a state of chaotic motion, "elastoinertial turbulence" (EIT), has been observed in a narrow Reynolds number interval. We here determine the origin of EIT in experiments and show that characteristic EIT structures can be detected across an unexpectedly wide range of parameters. Close to onset, a pattern of chevron-shaped streaks emerges in qualitative agreement with linear and weakly nonlinear theory. However, in experiments, the dynamics remain weakly chaotic, and the instability can be traced to far lower Reynolds numbers than permitted by theory. For increasing inertia, the flow undergoes a transformation to a wall mode composed of inclined near-wall streaks and shear layers. This mode persists to what is known as the "maximum drag reduction limit," and overall EIT is found to dominate viscoelastic flows across more than three orders of magnitude in Reynolds number.}, } @article {pmid34732141, year = {2021}, author = {Zhou, Y and Wang, DM and Liu, L and Huang, P}, title = {The morphometric of lycopsid sporophylls and the evaluation of their dispersal potential: an example from the Upper Devonian of Zhejiang Province, China.}, journal = {BMC ecology and evolution}, volume = {21}, number = {1}, pages = {198}, pmid = {34732141}, issn = {2730-7182}, mesh = {China ; *Fossils ; }, abstract = {BACKGROUND: Previous studies have discussed the special structural adaptations of Late Palaeozoic lycopsids, for example, the dispersal potential of reproductive organs. Based on materials from the Upper Devonian Wutong Formation in Changxing County, Zhejiang Province, China, we now analyze the morphometric and perform some calculation to evaluate the dispersal of sporophyll units of lycopsids.

RESULTS: The fossil sporophyll units are divided into two types in view of obvious difference in shape and we name two new (form) species for them. We also analyze the falling process and give the calculation method of dispersal distance.

CONCLUSIONS: The fossil sporophyll units show relatively poor potential of wind dispersal compared with modern samaras, and show potential adaptation to the turbulent environment.}, } @article {pmid34731319, year = {2021}, author = {Miles, JG and Battista, NA}, title = {Exploring the sensitivity in jellyfish locomotion under variations in scale, frequency, and duty cycle.}, journal = {Journal of mathematical biology}, volume = {83}, number = {5}, pages = {56}, pmid = {34731319}, issn = {1432-1416}, mesh = {Animals ; Biomechanical Phenomena ; Locomotion ; *Models, Biological ; *Scyphozoa ; Swimming ; }, abstract = {Jellyfish have been called one of the most energy-efficient animals in the world due to the ease in which they move through their fluid environment, by product of their bell kinematics coupled with their morphological, muscular, material properties. We investigated jellyfish locomotion by conducting in silico comparative studies and explored swimming performance across different fluid scales (i.e., Reynolds Number), bell contraction frequencies, and contraction phase kinematics (duty cycle) for a jellyfish with a fineness ratio of 1 (ratio of bell height to bell diameter). To study these relationships, an open source implementation of the immersed boundary method was used (IB2d) to solve the fully coupled fluid-structure interaction problem of a flexible jellyfish bell in a viscous fluid. Thorough 2D parameter subspace explorations illustrated optimal parameter combinations in which give rise to enhanced swimming performance. All performance metrics indicated a higher sensitivity to bell actuation frequency than fluid scale or duty cycle, via Sobol sensitivity analysis, on a higher performance parameter subspace. Moreover, Pareto-like fronts were identified in the overall performance space involving the cost of transport and forward swimming speed. Patterns emerged within these performance spaces when highlighting different parameter regions, which complemented the global sensitivity results. Lastly, an open source computational model for jellyfish locomotion is offered to the science community that can be used as a starting place for future numerical experimentation.}, } @article {pmid34693101, year = {2021}, author = {Grande Gutiérrez, N and Shankar, KN and Sinno, T and Diamond, SL}, title = {Thrombosis and Hemodynamics: external and intrathrombus gradients.}, journal = {Current opinion in biomedical engineering}, volume = {19}, number = {}, pages = {}, pmid = {34693101}, issn = {2468-4511}, support = {R01 HL103419/HL/NHLBI NIH HHS/United States ; U01 HL131053/HL/NHLBI NIH HHS/United States ; }, abstract = {Distinct from dilute, isotropic, and homogeneous reaction systems typically used in laboratory kinetic assays, blood is concentrated, two-phase, flowing, and highly anisotropic when clotting on a surface. This review focuses on spatial gradients that are generated and can dictate thrombus structure and function. Novel experimental and computational tools have recently emerged to explore reaction-transport coupling during clotting. Multiscale simulations help bridge tissue length scales (the coronary arteries) to millimeter scales of a growing clot to the microscopic scale of single-cell signaling and adhesion. Microfluidic devices help create and control pathological velocity profiles, albeit at a low Reynolds number. Since rate processes and force loading are often coupled, this review highlights prevailing convective-diffusive transport physics that modulate cellular and molecular processes during thrombus formation.}, } @article {pmid34685088, year = {2021}, author = {Sun, X and Mohammed, HI and Tiji, ME and Mahdi, JM and Majdi, HS and Wang, Z and Talebizadehsardari, P and Yaïci, W}, title = {Investigation of Heat Transfer Enhancement in a Triple Tube Latent Heat Storage System Using Circular Fins with Inline and Staggered Arrangements.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {11}, number = {10}, pages = {}, pmid = {34685088}, issn = {2079-4991}, abstract = {Inherent fluctuations in the availability of energy from renewables, particularly solar, remain a substantial impediment to their widespread deployment worldwide. Employing phase-change materials (PCMs) as media, saving energy for later consumption, offers a promising solution for overcoming the problem. However, the heat conductivities of most PCMs are limited, which severely limits the energy storage potential of these materials. This study suggests employing circular fins with staggered distribution to achieve improved thermal response rates of PCM in a vertical triple-tube heat exchanger involving two opposite flow streams of the heat-transfer fluid (HTF). Since heat diffusion is not the same at various portions of the PCM unit, different fin configurations, fin dimensions and HTF flow boundary conditions were explored using computational studies of melting in the PCM triple-tube system. Staggered configuration of fin distribution resulted in significant increases in the rates of PCM melting. The results indicate that the melting rate and heat charging rate could be increased by 37.2 and 59.1%, respectively, in the case of staggered distribution. Furthermore, the use of lengthy fins with smaller thickness in the vertical direction of the storage unit resulted in a better positive role of natural convection; thus, faster melting rates were achieved. With fin dimensions of 0.666 mm × 15 mm, the melting rate was found to be increased by 23.6%, when compared to the base case of 2 mm × 5 mm. Finally, it was confirmed that the values of the Reynolds number and inlet temperatures of the HTF had a significant impact on melting time savings when circular fins of staggered distribution were included.}, } @article {pmid34683293, year = {2021}, author = {Yamashita, H and Akinaga, T and Sugihara-Seki, M}, title = {Pattern Transition on Inertial Focusing of Neutrally Buoyant Particles Suspended in Rectangular Duct Flows.}, journal = {Micromachines}, volume = {12}, number = {10}, pages = {}, pmid = {34683293}, issn = {2072-666X}, support = {JP20H02072//JSPS KAKENHI/ ; }, abstract = {The continuous separation and filtration of particles immersed in fluid flows are important interests in various applications. Although the inertial focusing of particles suspended in a duct flow is promising in microfluidics, predicting the focusing positions depending on the parameters, such as the shape of the duct cross-section and the Reynolds number (Re) has not been achieved owing to the diversity of the inertial-focusing phenomena. In this study, we aimed to elucidate the variation of the inertial focusing depending on Re in rectangular duct flows. We performed a numerical simulation of the lift force exerted on a spherical particle flowing in a rectangular duct and determined the lift-force map within the duct cross-section over a wide range of Re. We estimated the particle trajectories based on the lift map and Stokes drag, and identified the particle-focusing points appeared in the cross-section. For an aspect ratio of the duct cross-section of 2, we found that the blockage ratio changes transition structure of particle focusing. For blockage ratios smaller than 0.3, particles focus near the centres of the long sides of the cross-section at low Re and near the centres of both the long and short sides at relatively higher Re. This transition is expressed as a subcritical pitchfork bifurcation. For blockage ratio larger than 0.3, another focusing pattern appears between these two focusing regimes, where particles are focused on the centres of the long sides and at intermediate positions near the corners. Thus, there are three regimes; the transition between adjacent regimes at lower Re is found to be expressed as a saddle-node bifurcation and the other transition as a supercritical pitchfork bifurcation.}, } @article {pmid34678790, year = {2021}, author = {Christov, IC}, title = {Soft hydraulics: from Newtonian to complex fluid flows through compliant conduits.}, journal = {Journal of physics. Condensed matter : an Institute of Physics journal}, volume = {34}, number = {6}, pages = {}, doi = {10.1088/1361-648X/ac327d}, pmid = {34678790}, issn = {1361-648X}, mesh = {Cross-Sectional Studies ; *Hydrodynamics ; Lab-On-A-Chip Devices ; *Microfluidics/methods ; Viscosity ; }, abstract = {Microfluidic devices manufactured from soft polymeric materials have emerged as a paradigm for cheap, disposable and easy-to-prototype fluidic platforms for integrating chemical and biological assays and analyses. The interplay between the flow forces and the inherently compliant conduits of such microfluidic devices requires careful consideration. While mechanical compliance was initially a side-effect of the manufacturing process and materials used, compliance has now become a paradigm, enabling new approaches to microrheological measurements, new modalities of micromixing, and improved sieving of micro- and nano-particles, to name a few applications. This topical review provides an introduction to the physics of these systems. Specifically, the goal of this review is to summarize the recent progress towards a mechanistic understanding of the interaction between non-Newtonian (complex) fluid flows and their deformable confining boundaries. In this context, key experimental results and relevant applications are also explored, hand-in-hand with the fundamental principles for their physics-based modeling. The key topics covered include shear-dependent viscosity of non-Newtonian fluids, hydrodynamic pressure gradients during flow, the elastic response (deformation and bulging) of soft conduits due to flow within, the effect of cross-sectional conduit geometry on the resulting fluid-structure interaction, and key dimensionless groups describing the coupled physics. Open problems and future directions in this nascent field of soft hydraulics, at the intersection of non-Newtonian fluid mechanics, soft matter physics, and microfluidics, are noted.}, } @article {pmid34677517, year = {2021}, author = {Park, NS and Yoon, S and Jeong, W and Jeong, YW}, title = {A Study on the Evaluation of Flow Distribution Evenness in Parallel-Arrayed-Type Low-Pressure Membrane Module Piping.}, journal = {Membranes}, volume = {11}, number = {10}, pages = {}, pmid = {34677517}, issn = {2077-0375}, support = {No. 2020R1A2C1006495//National Research Foundation of Korea (NRF)/ ; }, abstract = {The objectives of this study were to measure the flow rate distribution from a header pipe to each module installed in parallel for a water treatment membrane filtration process in operation and to investigate the reason for an uneven distribution of the flow rate via the CFD technique. In addition, this study attempted to propose the ratio of the branch pipe to the header pipe required to equalize the flow distribution for the same membrane filtration process. Finally, the relationship between the Reynolds number in the header pipe and the degree of the manifold flow distribution evenness was investigated. Mobile ultrasonic flow meter was used to measure the flow rate flowing from the membrane module pipe to each module, and the CFD technique was used to verify this. From the results of the actual measurement using ultrasonic flow meter and CFD simulation, it was confirmed that the outflow flow rate from the branch pipe located at the end of the header pipe was three times higher than that of the branch pipe near the inlet. The reason was that the differential pressure generated between each membrane module was higher toward the end of the header pipe. When the ratio of the sum of the cross-sectional area of the branch pipe and the cross-sectional area of the header pipe was reduced by about 30 times, it was confirmed that the flow rate flowing from each branch pipe to the membrane module was almost equal. Also, if the flow in the header pipe is transitional or laminar (Reynolds No. is approximately 4000 or less), the flow rate flowing from each branch pipe to the membrane module can be more even.}, } @article {pmid34677490, year = {2021}, author = {Kim, KT and Park, JE and Jung, SY and Kang, TG}, title = {Fouling Mitigation via Chaotic Advection in a Flat Membrane Module with a Patterned Surface.}, journal = {Membranes}, volume = {11}, number = {10}, pages = {}, pmid = {34677490}, issn = {2077-0375}, support = {2019R1F1A1058001//National Research Foundation of Korea/ ; }, abstract = {Fouling mitigation using chaotic advection caused by herringbone-shaped grooves in a flat membrane module is numerically investigated. The feed flow is laminar with the Reynolds number (Re) ranging from 50 to 500. In addition, we assume a constant permeate flux on the membrane surface. Typical flow characteristics include two counter-rotating flows and downwelling flows, which are highly influenced by the groove depth at each Re. Poincaré sections are plotted to represent the dynamical systems of the flows and to analyze mixing. The flow systems become globally chaotic as the groove depth increases above a threshold value. Fouling mitigation via chaotic advection is demonstrated using the dimensionless average concentration (c¯w*) on the membrane and its growth rate. When the flow system is chaotic, the growth rate of c¯w* drops significantly compared to that predicted from the film theory, demonstrating that chaotic advection is an attractive hydrodynamic technique that mitigates membrane fouling. At each Re, there exists an optimal groove depth minimizing c¯w* and the growth rate of c¯w*. Under the optimum groove geometry, foulants near the membrane are transported back to the bulk flow via the downwelling flows, distributed uniformly in the entire channel via chaotic advection.}, } @article {pmid34663851, year = {2021}, author = {Khan, WU and Imran, A and Raja, MAZ and Shoaib, M and Awan, SE and Kausar, K and He, Y}, title = {A novel mathematical modeling with solution for movement of fluid through ciliary caused metachronal waves in a channel.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {20601}, pmid = {34663851}, issn = {2045-2322}, abstract = {In the present research, a novel mathematical model for the motion of cilia using non-linear rheological fluid in a symmetric channel is developed. The strength of analytical perturbation technique is employed for the solution of proposed physical process using mectachoronal rhythm based on Cilia induced flow for pseudo plastic nano fluid model by considering the low Reynolds number and long wave length approximation phenomena. The role of ciliary motion for the fluid transport in various animals is explained. Analytical expressions are gathered for stream function, concentration, temperature profiles, axial velocity, and pressure gradient. Whereas, transverse velocity, pressure rise per wave length, and frictional force on the wall of the tubule are investigated with aid of numerical computations and their outcomes are demonstrated graphically. A comprehensive analysis for comparison of Perturb and numerical solution is done. This analysis validates the analytical solution.}, } @article {pmid34659649, year = {2022}, author = {Cui, PY and Chen, WQ and Wang, JQ and Zhang, JH and Huang, YD and Tao, WQ}, title = {Numerical studies on issues of Re-independence for indoor airflow and pollutant dispersion within an isolated building.}, journal = {Building simulation}, volume = {15}, number = {7}, pages = {1259-1276}, pmid = {34659649}, issn = {1996-3599}, abstract = {This study conducted the numerical models validated by wind-tunnel experiments to investigate the issues of Re-independence of indoor airflow and pollutant dispersion within an isolated building. The window Reynolds number (Re w) was specified to characterize the indoor flow and dispersion. The indicators of RRC (ratio of relative change) or DR (K_DR) (difference ratio of dimensionless concentration) ≤ 5% were applied to quantitatively determine the critical Re w for indoor flow and turbulent diffusion. The results show that the critical Re (Re crit) value is position-dependent, and Re crit at the most unfavorable position should be suggested as the optimal value within the whole areas of interest. Thus Re H,crit = 27,000 is recommended for the outdoor flows; while Re w,crit = 15,000 is determined for the indoor flows due to the lower part below the window showing the most unfavorable. The suggested Re w,crit (=15,000) for indoor airflow and cross ventilation is independence of the window size. Moreover, taking K_DR ≤ 5% as the indicator, the suggested Re w,crit for ensuring indoor pollutant diffusion enter the Re-independence regime should also be 15,000, indicating that indoor passive diffusion is completely determined by the flow structures. The contours of dimensionless velocity (U/U 0) and concentration (K) against the increasing Re w further confirmed this critical value. This study further reveals the Re-independence issues for indoor flow and dispersion to ensure the reliability of the data obtained by reduced-scale numerical or wind-tunnel models.}, } @article {pmid34656560, year = {2022}, author = {Moitoi, AJ and Shaw, S}, title = {Magnetic drug targeting during Caputo-Fabrizio fractionalized blood flow through a permeable vessel.}, journal = {Microvascular research}, volume = {139}, number = {}, pages = {104262}, doi = {10.1016/j.mvr.2021.104262}, pmid = {34656560}, issn = {1095-9319}, mesh = {Antineoplastic Agents/*blood/chemistry/therapeutic use ; Blood Vessels/*metabolism ; Computer Simulation ; *Drug Carriers ; Drug Compounding ; *Magnetic Fields ; *Metal Nanoparticles ; *Models, Cardiovascular ; Nanotechnology ; Neoplasms/*blood supply/drug therapy/metabolism ; Numerical Analysis, Computer-Assisted ; Permeability ; Regional Blood Flow ; }, abstract = {Nanoparticle-based drug targeting is an important platform for the treatment of cardiovascular disorders. Magnetic drug targeting is more significant as it is a noninvasive procedure and biocompatible. The present problem aims to understand magnetic drug delivery to a specific location in a permeable blood vessel under the vibration and magnetic environment. Caputo-Fabrizio fractional-order time derivatives are used in the governing equations. The momentum equations are solved analytically and presented in the form of Lorenzo-Hartley and Robotonov-Hartley functions and convolution of the Laplace transform. Convolution integrations are solved by using the numerical integration technique. The Fourth order Runge-Kutta method (RK4) is used to solve the force balance equation. The influence of pertinent parameters such as Reynolds number, pulsatile frequency, magnetic field strength, Darcy number and fractional-order parameters are presented through graphs. It is observed that increasing Reynolds number results in decreasing the tendency of the drug to capture near the tumor site, whereas the pulsatile frequency presents an opposite phenomenon. Increasing the magnetic field strength and Darcy number boosts the capture efficiency of drug particles near the tumor site. The short memory effect efficiently captures the magnetic drug carriers to a specific location under the action of suitable magnetic field strength.}, } @article {pmid34654198, year = {2021}, author = {Calderer, MC and Golovaty, D and Yao, L and Zhao, L}, title = {Shear flow of active matter in thin channels.}, journal = {Physical review. E}, volume = {104}, number = {3-1}, pages = {034607}, doi = {10.1103/PhysRevE.104.034607}, pmid = {34654198}, issn = {2470-0053}, abstract = {We study the shear flow of active filaments confined in a thin channel for extensile and contractile fibers. We apply the Ericksen-Leslie equations of liquid crystal flow with an activity source term. The dimensionless form of this system includes the Ericksen, activity, and Reynolds numbers, together with the aspect ratio of the channel, as the main driving parameters. We perform a normal mode stability analysis of the base shear flow. For both types of fibers, we arrive at a comprehensive description of the stability properties and their dependence on the parameters of the system. The transition to unstable frequencies in extensile fibers occurs at a positive threshold value of the activity parameter, whereas for contractile ones a complex behavior is found at low absolute value of the activity number. The latter might be an indication of the biologically relevant plasticity and phase transition issues. In contrast with extensile fibers, flows of contractile ones are also found to be highly sensitive to the Reynolds number. The work on extensile fibers is guided by experiments on active filaments in confined channels and aims at quantifying their findings in the prechaotic regime.}, } @article {pmid34651149, year = {2021}, author = {Gallen, AF and Castro, M and Hernandez-Machado, A}, title = {Red blood cells in low Reynolds number flow: A vorticity-based characterization of shapes in two dimensions.}, journal = {Soft matter}, volume = {17}, number = {42}, pages = {9587-9594}, doi = {10.1039/d1sm00559f}, pmid = {34651149}, issn = {1744-6848}, mesh = {Cell Movement ; Cell Shape ; *Erythrocytes ; *Hydrodynamics ; Physical Phenomena ; }, abstract = {Studies on the mechanical properties of red blood cells improve the diagnosis of some blood-related diseases. Some existing numerical methods have successfully simulated the coupling between a fluid and red blood cells. This paper introduces an alternative phase-field model formulation of two-dimensional cells that solves the vorticity and stream function that simplifies the numerical implementation. We integrate red blood cell dynamics immersed in a Poiseuille flow and reproduce previously reported morphologies (slippers or parachutes). In the case of flow in a very wide channel, we discover a new metastable shape referred to as 'anti-parachute' that evolves into a horizontal slipper centered on the channel. This sort of metastable morphology may contribute to the dynamical response of the blood.}, } @article {pmid34644682, year = {2022}, author = {Truong, H and Engels, T and Wehmann, H and Kolomenskiy, D and Lehmann, FO and Schneider, K}, title = {An experimental data-driven mass-spring model of flexibleCalliphorawings.}, journal = {Bioinspiration & biomimetics}, volume = {17}, number = {2}, pages = {}, doi = {10.1088/1748-3190/ac2f56}, pmid = {34644682}, issn = {1748-3190}, mesh = {Animals ; Biomechanical Phenomena ; Elasticity ; *Flight, Animal ; Humans ; Insecta ; Models, Biological ; *Wings, Animal ; }, abstract = {Insect wings can undergo significant deformation during flapping motion owing to inertial, elastic and aerodynamic forces. Changes in shape then alter aerodynamic forces, resulting in a fully coupled fluid-structure interaction (FSI) problem. Here, we present detailed three-dimensional FSI simulations of deformable blowfly (Calliphora vomitoria) wings in flapping flight. A wing model is proposed using a multi-parameter mass-spring approach, chosen for its implementation simplicity and computational efficiency. We train the model to reproduce static elasticity measurements by optimizing its parameters using a genetic algorithm with covariance matrix adaptation (CMA-ES). Wing models trained with experimental data are then coupled to a high-performance flow solver run on massively parallel supercomputers. Different features of the modeling approach and the intra-species variability of elastic properties are discussed. We found that individuals with different wing stiffness exhibit similar aerodynamic properties characterized by dimensionless forces and power at the same Reynolds number. We further study the influence of wing flexibility by comparing between the flexible wings and their rigid counterparts. Under equal prescribed kinematic conditions for rigid and flexible wings, wing flexibility improves lift-to-drag ratio as well as lift-to-power ratio and reduces peak force observed during wing rotation.}, } @article {pmid34642447, year = {2021}, author = {Ali, A and Kanwal, T and Awais, M and Shah, Z and Kumam, P and Thounthong, P}, title = {Impact of thermal radiation and non-uniform heat flux on MHD hybrid nanofluid along a stretching cylinder.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {20262}, pmid = {34642447}, issn = {2045-2322}, abstract = {The current research investigates the thermal radiations and non-uniform heat flux impacts on magnetohydrodynamic hybrid nanofluid (CuO-Fe2O3/H2O) flow along a stretching cylinder, which is the main aim of this study. The velocity slip conditions have been invoked to investigate the slippage phenomenon on the flow. The impact of induced magnetic field with the assumption of low Reynolds number is imperceptible. Through the use of appropriate non-dimensional parameters and similarity transformations, the ruling PDE's (partial differential equations) are reduced to set of ODE's (ordinary differential equations), which are then numerically solved using Adams-Bashforth Predictor-Corrector method. Velocity and temperature fields with distinct physical parameters are investigated and explored graphically. The main observations about the hybrid nanofluid and non-uniform heat flux are analyzed graphically. A decrease in the velocity of the fluid is noted with addition of Hybrid nanofluid particles while temperature of the fluid increases by adding the CuO-Fe2O3 particles to the base fluid. Also, velocity of the fluid decreases when we incorporate the effects of magnetic field and slip. Raise in curvature parameter γ caused enhancement of velocity and temperature fields at a distance from the cylinder but displays opposite behavior nearby the surface of cylinder. The existence of heat generation and absorption for both mass dependent and time dependent parameters increases the temperature of the fluid.}, } @article {pmid34636830, year = {2021}, author = {Ho, TM and Yang, J and Tsai, PA}, title = {Microfluidic mass transfer of CO2 at elevated pressures: implications for carbon storage in deep saline aquifers.}, journal = {Lab on a chip}, volume = {21}, number = {20}, pages = {3942-3951}, doi = {10.1039/d1lc00106j}, pmid = {34636830}, issn = {1473-0189}, mesh = {*Carbon Dioxide ; *Groundwater ; Microfluidics ; Water ; }, abstract = {Carbon capture and sequestration (CCS) in a deep saline aquifer is one of the most promising technologies to mitigate anthropologically emitted carbon dioxide. Accurately quantifying the mass transport of CO2 at pore-scales is crucial but challenging for successful CCS deployment. Here, we conduct high-pressure microfluidic experiments, mimicking reservoir conditions up to 9.5 MPa and 35 °C, to elucidate the microfluidic mass transfer process of CO2 at three different states (i.e., gas, liquid, and supercritical phase) into water. We measure the size change of CO2 micro-bubbles/droplets generated using a microfluidic T-junction to estimate the volumetric mass transfer coefficient (kLa), quantifying the rate change of CO2 concentration under the driving force of concentration gradient. The results show that bubbles/droplets under high-pressure conditions reach a steady state faster than low pressure. The measured volumetric mass transfer coefficient increases with the Reynolds number (based on the liquid slug) and is nearly independent of the injection pressure for both the gas and liquid phases. In addition, kLa significantly enlarges with increasing high pressure at the supercritical state. Compared with various chemical engineering applications using millimeter-sized capillaries (with typical kLa measured ranging from ≈0.005 to 0.8 s[-1]), the microfluidic results show a significant increase in the volumetric mass transfer of CO2 into water by two to three orders of magnitude, O (10[2]-10[3]), with decreasing hydrodynamic diameter (of ≈50 μm).}, } @article {pmid34635693, year = {2021}, author = {Liao, Y and Mechulam, Y and Lassalle-Kaiser, B}, title = {A millisecond passive micromixer with low flow rate, low sample consumption and easy fabrication.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {20119}, pmid = {34635693}, issn = {2045-2322}, mesh = {Complex Mixtures/*analysis ; *Computer Simulation ; Equipment Design ; Humans ; Lab-On-A-Chip Devices/*standards ; Microfluidic Analytical Techniques/*instrumentation/*methods ; }, abstract = {Fast mixing of small volumes of solutions in microfluidic devices is essential for an accurate control and observation of the dynamics of a reaction in biological or chemical studies. It is often, however, a challenging task, as the Reynolds number (Re) in microscopic devices is typically < 100. In this report, we detail a novel mixer based on the "staggered herring bone" (SHB) pattern and "split-recombination" strategies with an optimized geometry, the periodic rotation of the flow structure can be controlled and recombined in a way that the vortices and phase shifts of the flow induce intertwined lamellar structures, thus increasing the contact surface and enhancing mixing. The optimization improves the mixing while using a low flow rate, hence a small volume for mixing and moderate pressure drops. The performances of the patterns were first simulated using COMSOL Multiphysics under different operating conditions. The simulation indicates that at very low flow rate (1-12 µL·min[-1]) and Re (3.3-40), as well as a very small working volume (~ 3 nL), a very good mixing (~ 98%) can be achieved in the ms time range (4.5-78 ms). The most promising design was then visualized experimentally, showing results that are consistent with the outcomes of the simulations. Importantly, the devices were fabricated using a classical soft-lithography method, as opposed to additive manufacturing often used to generate complex mixing structures. This new device minimizes the sample consumption and could therefore be applied for studies using precious samples.}, } @article {pmid34625588, year = {2021}, author = {Hussain, A and Hassan, A and Mdallal, QA and Ahmad, H and Sherif, EM and Rehman, A and Arshad, M}, title = {Comsolic solution of an elliptic cylindrical compressible fluid flow.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {20030}, pmid = {34625588}, issn = {2045-2322}, abstract = {In this article, the primary focus is to investigate the heat transfer effects with viscous compressible laminar flow in the permeable elliptic cylinder. The Reynolds number is kept 100 for flow to be laminar. The physics of heat transfer is selected to be coupled with the laminar flow. The results for particular step-size time for Velocity distribution, pressure profile, temperature profile, isothermal temperature contours, and drag coefficient have been analyzed. Mesh has been generated through COMSOL, mesh entities have been elaborated statistically. The maximum and minimum velocity profile is observed at the elliptical cylinder's walls and upper, lower boundary respectively. The maximum velocity observed is 2.22 m/s. Pressure profile around elliptic corners is found maximum, distinct patterns are observed even under the influence of applied heat. Temperature is observed maximum at walls but it gradually increases as moving from the upper boundary towards the lower boundary. The isothermal contour patterns are observed maximum near the walls, drag coefficient of gradual decrease is observed. COMSOL multi-physics is utilized for mathematical modeling of problems and the Backward-Differentiation-Formula has been exploited to handle problems numerically. The results will help greatly to understand the characterizations of viscous fluids and in industries like air furnaces and automobile cooling systems.}, } @article {pmid34623848, year = {2021}, author = {Khalid, M and Shankar, V and Subramanian, G}, title = {Continuous Pathway between the Elasto-Inertial and Elastic Turbulent States in Viscoelastic Channel Flow.}, journal = {Physical review letters}, volume = {127}, number = {13}, pages = {134502}, doi = {10.1103/PhysRevLett.127.134502}, pmid = {34623848}, issn = {1079-7114}, abstract = {Viscoelastic plane Poiseuille flow is shown to become linearly unstable in the absence of inertia, in the limit of high elasticities, for ultradilute polymer solutions. While inertialess elastic instabilities have been predicted for curvilinear shear flows, this is the first ever report of a purely elastic linear instability in a rectilinear shear flow. The novel instability continues up to a Reynolds number (Re) of O(1000), corresponding to the recently identified elasto-inertial turbulent state believed to underlie the maximum-drag-reduced regime. Thus, for highly elastic ultradilute polymer solutions, a single linearly unstable modal branch may underlie transition to elastic turbulence at zero Re and to elasto-inertial turbulence at moderate Re, implying the existence of continuous pathways connecting the turbulent states to each other and to the laminar base state.}, } @article {pmid34608161, year = {2021}, author = {Marusic, I and Chandran, D and Rouhi, A and Fu, MK and Wine, D and Holloway, B and Chung, D and Smits, AJ}, title = {An energy-efficient pathway to turbulent drag reduction.}, journal = {Nature communications}, volume = {12}, number = {1}, pages = {5805}, pmid = {34608161}, issn = {2041-1723}, abstract = {Simulations and experiments at low Reynolds numbers have suggested that skin-friction drag generated by turbulent fluid flow over a surface can be decreased by oscillatory motion in the surface, with the amount of drag reduction predicted to decline with increasing Reynolds number. Here, we report direct measurements of substantial drag reduction achieved by using spanwise surface oscillations at high friction Reynolds numbers ([Formula: see text]) up to 12,800. The drag reduction occurs via two distinct physical pathways. The first pathway, as studied previously, involves actuating the surface at frequencies comparable to those of the small-scale eddies that dominate turbulence near the surface. We show that this strategy leads to drag reduction levels up to 25% at [Formula: see text] = 6,000, but with a power cost that exceeds any drag-reduction savings. The second pathway is new, and it involves actuation at frequencies comparable to those of the large-scale eddies farther from the surface. This alternate pathway produces drag reduction of 13% at [Formula: see text] = 12,800. It requires significantly less power and the drag reduction grows with Reynolds number, thereby opening up potential new avenues for reducing fuel consumption by transport vehicles and increasing power generation by wind turbines.}, } @article {pmid34607142, year = {2022}, author = {Yogarathinam, LT and Velswamy, K and Gangasalam, A and Ismail, AF and Goh, PS and Narayanan, A and Abdullah, MS}, title = {Performance evaluation of whey flux in dead-end and cross-flow modes via convolutional neural networks.}, journal = {Journal of environmental management}, volume = {301}, number = {}, pages = {113872}, doi = {10.1016/j.jenvman.2021.113872}, pmid = {34607142}, issn = {1095-8630}, mesh = {*Cheese/analysis ; Filtration ; Membranes, Artificial ; Neural Networks, Computer ; *Whey ; Whey Proteins ; }, abstract = {Effluent originating from cheese production puts pressure onto environment due to its high organic load. Therefore, the main objective of this work was to compare the influence of different process variables (transmembrane pressure (TMP), Reynolds number and feed pH) on whey protein recovery from synthetic and industrial cheese whey using polyethersulfone (PES 30 kDa) membrane in dead-end and cross-flow modes. Analysis on the fouling mechanistic model indicates that cake layer formation is dominant as compared to other pore blocking phenomena evaluated. Among the input variables, pH of whey protein solution has the biggest influence towards membrane flux and protein rejection performances. At pH 4, electrostatic attraction experienced by whey protein molecules prompted a decline in flux. Cross-flow filtration system exhibited a whey rejection value of 0.97 with an average flux of 69.40 L/m[2]h and at an experimental condition of 250 kPa and 8 for TMP and pH, respectively. The dynamic behavior of whey effluent flux was modeled using machine learning (ML) tool convolutional neural networks (CNN) and recursive one-step prediction scheme was utilized. Linear and non-linear correlation indicated that CNN model (R[2] - 0.99) correlated well with the dynamic flux experimental data. PES 30 kDa membrane displayed a total protein rejection coefficient of 0.96 with 55% of water recovery for the industrial cheese whey effluent. Overall, these filtration studies revealed that this dynamic whey flux data studies using the CNN modeling also has a wider scope as it can be applied in sensor tuning to monitor flux online by means of enhancing whey recovery efficiency.}, } @article {pmid34599248, year = {2021}, author = {Almalki, MM and Alaidarous, ES and Maturi, DA and Raja, MAZ and Shoaib, M}, title = {Intelligent computing technique based supervised learning for squeezing flow model.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {19597}, pmid = {34599248}, issn = {2045-2322}, abstract = {In this study, the unsteady squeezing flow between circular parallel plates (USF-CPP) is investigated through the intelligent computing paradigm of Levenberg-Marquard backpropagation neural networks (LMBNN). Similarity transformation introduces the fluidic system of the governing partial differential equations into nonlinear ordinary differential equations. A dataset is generated based on squeezing fluid flow system USF-CPP for the LMBNN through the Runge-Kutta method by the suitable variations of Reynolds number and volume flow rate. To attain approximation solutions for USF-CPP to different scenarios and cases of LMBNN, the operations of training, testing, and validation are prepared and then the outcomes are compared with the reference data set to ensure the suggested model's accuracy. The output of LMBNN is discussed by the mean square error, dynamics of state transition, analysis of error histograms, and regression illustrations.}, } @article {pmid34588473, year = {2021}, author = {Ramzan, M and Khan, NS and Kumam, P}, title = {Mechanical analysis of non-Newtonian nanofluid past a thin needle with dipole effect and entropic characteristics.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {19378}, pmid = {34588473}, issn = {2045-2322}, abstract = {The study concerns with the mechanical characteristics of heat and mass transfer flow of a second grade nanofluid as well as gyrotatic microorganism motion past a thin needle with dipole effect, entropy generation, thermal radiation, Arrhenius activation energy and binar chemical reaction. The governing equations and boundary conditions are simplified by the use of suitable similarity transformations. Homotopy analysis method is implemented to obtain the series solution of non-linear ordinary differential equations. Physical behaviors of heat and mass transfer flow with gyrotatic microorganisms and entropy generation are investigated through the embedded parameters. The nanofluid velocity is enhanced for higher values of the ferromagnetic parameter, local Grashof number, bioconvection Rayleigh number and radiation parameter. The Reynolds number, radiation parameter and Eckert number decrease the nanofluid temperature. The entropy generation is increased with the enhancement of radiation parameter, Eckert number, Lewis number, temperature difference parameter, dimensionless constant parameter, Curie temperature, Prandtl number and concentration difference parameter.}, } @article {pmid34586089, year = {2021}, author = {Treiser, MD and Miles, MR and Albino, FP and Giladi, AM and Katz, RD and Higgins, JP}, title = {Long-Term Patency and Fluid Dynamics of Recipient Artery after End-to-Side Anastomosis for Free Tissue Transfer.}, journal = {Plastic and reconstructive surgery}, volume = {148}, number = {5}, pages = {800e-803e}, doi = {10.1097/PRS.0000000000008439}, pmid = {34586089}, issn = {1529-4242}, mesh = {Adolescent ; Adult ; Anastomosis, Surgical/methods ; Arteries/diagnostic imaging/physiology/*surgery ; Blood Flow Velocity ; Collateral Circulation ; Extremities/blood supply/*injuries/surgery ; Follow-Up Studies ; Free Tissue Flaps/blood supply/*transplantation ; Humans ; Middle Aged ; Plastic Surgery Procedures/*methods ; Treatment Outcome ; Ultrasonography, Doppler, Duplex ; *Vascular Patency ; Young Adult ; }, abstract = {BACKGROUND: End-to-end microvascular anastomoses sacrifice downstream inline perfusion of the recipient vessels. End-to-side anastomoses, in theory, maintain distal inline flow of the recipient vessel. The proposed benefit of the end-to-side technique depends on patency of the distal vessels and subsequent flow parameters, but maintenance of distal perfusion has not been conclusively demonstrated.

METHODS: Fifteen patients who underwent a successful extremity free flap procedure via end-to-side anastomoses to a noncritical vessel between 2003 and 2017 were enrolled. Recipient artery patency distal to the anastomosis was assessed using pulse volume recordings and duplex ultrasound imaging. Resistance indices, flow velocities, vessel diameters, volumetric flow, and turbulent flow dimensionless number (Reynolds number) were measured. Comparisons were made to the ipsilateral collateral vessel as well as to the vessels on the nonoperative contralateral limb using paired t tests.

RESULTS: Downstream flow was identified in 14 of 15 patients (93 percent patency). There was no statistical difference in resistive indices comparing the anastomotic vessel (0.859 ± 0.300) and the collateral vessel (0.853 ± 0.179) of the ipsilateral extremity. Ultrasound flows were similar; the anastomotic vessel demonstrated downstream volumetric flows of 139 ± 92.0 cm3/min versus 137 ± 41.6 cm3/min within the same vessel of the nonoperative contralateral limb. The anastomotic vessel had Reynolds numbers well below the turbulent threshold (448 ± 202 and 493 ± 127 for the anastomotic and nonoperative contralateral limb, respectively).

CONCLUSION: End-to-side anastomosis to noncritical vessels resulted in a 93 percent long-term recipient vessel patency rate, with no statistically significant changes in volumetric flows, resistive indices, or fluid dynamics in the vessels that remained patent.}, } @article {pmid34577719, year = {2021}, author = {Huang, L and Du, J and Zhu, Z}, title = {Neutrally Buoyant Particle Migration in Poiseuille Flow Driven by Pulsatile Velocity.}, journal = {Micromachines}, volume = {12}, number = {9}, pages = {}, pmid = {34577719}, issn = {2072-666X}, support = {11572107//National Natural Science Foundation of China/ ; GK199900299012-026//the Fundamental Research Funds for the Provincial Universities of Zhejiang/ ; }, abstract = {A neutrally buoyant circular particle migration in two-dimensional (2D) Poiseuille channel flow driven by pulsatile velocity is numerical studied by using immersed boundary-lattice Boltzmann method (IB-LBM). The effects of Reynolds number (25≤Re≤200) and blockage ratio (0.15≤k≤0.40) on particle migration driven by pulsatile and non-pulsatile velocity are all numerically investigated for comparison. The results show that, different from non-pulsatile cases, the particle will migrate back to channel centerline with underdamped oscillation during the time period with zero-velocity in pulsatile cases. The maximum lateral travel distance of the particle in one cycle of periodic motion will increase with increasing Re, while k has little impact. The quasi frequency of such oscillation has almost no business with Re and k. Moreover, Re plays an essential role in the damping ratio. Pulsatile flow field is ubiquitous in aorta and other arteries. This article is conducive to understanding nanoparticle migration in those arteries.}, } @article {pmid34577699, year = {2021}, author = {Farahinia, A and Jamaati, J and Niazmand, H and Zhang, W}, title = {Numerical Analysis of the Heterogeneity Effect on Electroosmotic Micromixers Based on the Standard Deviation of Concentration and Mixing Entropy Index.}, journal = {Micromachines}, volume = {12}, number = {9}, pages = {}, pmid = {34577699}, issn = {2072-666X}, abstract = {One approach to achieve a homogeneous mixture in microfluidic systems in the quickest time and shortest possible length is to employ electroosmotic flow characteristics with heterogeneous surface properties. Mixing using electroosmotic flow inside microchannels with homogeneous walls is done primarily under the influence of molecular diffusion, which is not strong enough to mix the fluids thoroughly. However, surface chemistry technology can help create desired patterns on microchannel walls to generate significant rotational currents and improve mixing efficiency remarkably. This study analyzes the function of a heterogeneous zeta-potential patch located on a microchannel wall in creating mixing inside a microchannel affected by electroosmotic flow and determines the optimal length to achieve the desired mixing rate. The approximate Helmholtz-Smoluchowski model is suggested to reduce computational costs and simplify the solving process. The results show that the heterogeneity length and location of the zeta-potential patch affect the final mixing proficiency. It was also observed that the slip coefficient on the wall has a more significant effect than the Reynolds number change on improving the mixing efficiency of electroosmotic micromixers, benefiting the heterogeneous distribution of zeta-potential. In addition, using a channel with a heterogeneous zeta-potential patch covered by a slip surface did not lead to an adequate mixing in low Reynolds numbers. Therefore, a homogeneous channel without any heterogeneity would be a priority in such a range of Reynolds numbers. However, increasing the Reynolds number and the presence of a slip coefficient on the heterogeneous channel wall enhances the mixing efficiency relative to the homogeneous one. It should be noted, though, that increasing the slip coefficient will make the mixing efficiency decrease sharply in any situation, especially in high Reynolds numbers.}, } @article {pmid34575038, year = {2021}, author = {Gimsa, J and Gimsa, U}, title = {Contributions to a Discussion of Spinosaurus aegyptiacus as a Capable Swimmer and Deep-Water Predator.}, journal = {Life (Basel, Switzerland)}, volume = {11}, number = {9}, pages = {}, pmid = {34575038}, issn = {2075-1729}, abstract = {The new findings on Spinosaurus' swim tail strongly suggest that Spinosaurus was a specialized deep-water predator. However, the tail must be seen in the context of the propelled body. The comparison of the flow characteristics of Spinosaurus with geometrically similar animals and their swimming abilities under water must take their Reynolds numbers into account and provide a common context for the properties of Spinosaurus' tail and dorsal sail. Head shape adaptations such as the head crest reduced hydrodynamic disturbance and facilitated stealthy advance, especially when hunting without visual contact, when Spinosaurus could have used its rostral integumentary mechanoreceptors for prey detection. The muscular neck permitted 'pivot' feeding, where the prey's escape abilities were overcome by rapid dorsoventral head movement, facilitated by crest-mediated lower friction.}, } @article {pmid34549120, year = {2021}, author = {Wu, R and Xie, F and Wei, J and Song, X and Yang, H and Lv, P and Yu, G}, title = {Study on Soot Emission Characteristics of Methane/Oxygen Inverse Diffusion Flame.}, journal = {ACS omega}, volume = {6}, number = {36}, pages = {23191-23202}, pmid = {34549120}, issn = {2470-1343}, abstract = {Inverse diffusion flame (IDF) is an effective and widely used reaction form in the process of noncatalytic partial oxidation (NC-POX) of gaseous hydrocarbons (such as natural gas and coke oven gas). However, soot is generated in the combustion chamber in the case of unreasonable feeding conditions, and thus causes serious damage to the wall and nozzle. In this study, the effects of the equivalence ratio ([O/C]e), the oxygen flow rate, and the Reynolds number on the soot and CH* emission characteristics of CH4/O2 inverse diffusion flame were comprehensively analyzed based on a hyperspectral imaging system. In addition, the relationship between CH* and soot is explored using Ansys Fluent simulation. The experimental results show that the soot radiation core generation area is located in the outer ring of the flame, and the radial distribution of the radiation intensity is bimodal. With the increase in [O/C]e, the initial position for soot radiation and the overall radiation intensity of soot decrease. In addition, the CH* radiation intensity decreases as [O/C]e increases, and CH* exists in the whole flame. The simulation results clearly show that the existence of CH* is conducive to soot production. The emission intensity and the core area of soot formation increase with the increase in the oxygen velocity. Additionally, the soot emission region increases and the flame tip changes from a round blunt to symmetrical tip with the increase in the Reynolds number.}, } @article {pmid34547732, year = {2021}, author = {Haider, N and Shahzad, A and Qadri, MNM and Shams, TA}, title = {Aerodynamic analysis of hummingbird-like hovering flight.}, journal = {Bioinspiration & biomimetics}, volume = {16}, number = {6}, pages = {}, doi = {10.1088/1748-3190/ac28eb}, pmid = {34547732}, issn = {1748-3190}, mesh = {Animals ; Biomechanical Phenomena ; Birds ; Computer Simulation ; *Flight, Animal ; Insecta ; Models, Biological ; *Wings, Animal ; }, abstract = {Flapping wing micro aerial vehicles are studied as the substitute for fixed and rotary wing micro aerial vehicles because of the advantages such as agility, maneuverability, and employability in confined environments. Hummingbird's sustainable hovering capability inspires many researchers to develop micro aerial vehicles with similar dynamics. In this research, a wing of a ruby-throated hummingbird is modeled as an insect wing using membrane and stiffeners. The effect of flexibility on the aerodynamic performance of a wing in hovering flight has been studied numerically by using a fluid-structure interaction scheme at a Reynolds number of 3000. Different wings have been developed by using different positions and thicknesses of the stiffeners. The chordwise and spanwise flexural stiffnesses of all the wings modeled in this work are comparable to insects of similar span and chord length. When the position of the stiffener is varied, the best-performing wing has an average lift coefficient of 0.51. Subsequently, the average lift coefficient is increased to 0.56 when the appropriate thickness of the stiffeners is chosen. The best flexible wing outperforms its rigid counterpart and produces lift and power economy comparable to a real hummingbird's wing. That is, the average lift coefficient and power economy of 0.56 and 0.88 for the best flexible wing as compared to 0.61 and 1.07 for the hummingbird's wing. It can be concluded that a simple manufacturable flexible wing design based on appropriate positioning and thickness of stiffeners can serve as a potential candidate for bio-inspired flapping-wing micro aerial vehicles.}, } @article {pmid34528156, year = {2021}, author = {Javid, K and Hassan, M and Tripathi, D and Khan, S and Bobescu, E and Bhatti, MM}, title = {Double-diffusion convective biomimetic flow of nanofluid in a complex divergent porous wavy medium under magnetic effects.}, journal = {Journal of biological physics}, volume = {47}, number = {4}, pages = {477-498}, pmid = {34528156}, issn = {1573-0689}, mesh = {*Biomimetics ; Diffusion ; *Magnetic Fields ; *Nanotechnology ; Porosity ; }, abstract = {We explore the physical influence of magnetic field on double-diffusive convection in complex biomimetic (peristaltic) propulsion of nanofluid through a two-dimensional divergent channel. Additionally, porosity effects along with rheological properties of the fluid are also retained in the analysis. The mathematical model is developed by equations of continuity, momentum, energy, and mass concentration. First, scaling analysis is introduced to simplify the rheological equations in the wave frame of reference and then get the final form of equations after applying the low Reynolds number and lubrication approach. The obtained equations are solved analytically by using integration method. Physical interpretation of velocity, pressure gradient, pumping phenomena, trapping phenomena, heat, and mass transfer mechanisms are discussed in detail under magnetic and porous environment. The magnitude of velocity profile is reduced by increasing Grashof parameter. The bolus circulations disappeared from trapping phenomena for larger strength of magnetic and porosity medium. The magnitude of temperature profile and mass concentration are increasing by enhancing the Brownian motion parameter. This study can be productive in manufacturing non-uniform and divergent shapes of micro-lab-chip devices for thermal engineering, industrial, and medical technologies.}, } @article {pmid34505131, year = {2022}, author = {Costa, RP and Simplice Talla Nwotchouang, B and Yao, J and Biswas, D and Casey, D and McKenzie, R and Steinman, DA and Loth, F}, title = {Transition to Turbulence Downstream of a Stenosis for Whole Blood and a Newtonian Analog Under Steady Flow Conditions.}, journal = {Journal of biomechanical engineering}, volume = {144}, number = {3}, pages = {}, doi = {10.1115/1.4052370}, pmid = {34505131}, issn = {1528-8951}, mesh = {Animals ; Blood Flow Velocity ; Constriction, Pathologic ; *Glycerol ; *Models, Cardiovascular ; Rheology ; Stress, Mechanical ; Swine ; Water ; }, abstract = {Blood, a multiphase fluid comprised of plasma, blood cells, and platelets, is known to exhibit a shear-thinning behavior at low shear rates and near-Newtonian behavior at higher shear rates. However, less is known about the impact of its multiphase nature on the transition to turbulence. In this study, we experimentally determined the critical Reynolds number at which the flow began to transition to turbulence downstream of eccentric stenosis for whole porcine blood and a Newtonian blood analog (water-glycerin mixture). Velocity profiles for both fluids were measured under steady-state flow conditions using an ultrasound Doppler probe placed 12 diameters downstream of eccentric stenosis. Velocity was recorded at 21 locations along the diameter at 11 different flow rates. Normalized turbulent kinetic energy was used to determine the critical Reynolds number for each fluid. Blood rheology was measured before and after each experiment. Tests were conducted on five samples of each fluid inside a temperature-controlled in vitro flow system. The viscosity at a shear rate of 1000 s-1 was used to define the Reynolds number for each fluid. The mean critical Reynolds numbers for blood and water-glycerin were 470 ± 27.5 and 395 ± 10, respectively, indicating a ∼19% delay in transition to turbulence for whole blood compared to the Newtonian fluid. This finding is consistent with a previous report for steady flow in a straight pipe, suggesting some aspect of blood rheology may serve to suppress, or at least delay, the onset of turbulence in vivo.}, } @article {pmid34497885, year = {2021}, author = {Bu, X and Zhou, S and Sun, M and Alheshibri, M and Khan, MS and Xie, G and Chelgani, SC}, title = {Exploring the Relationships between Gas Dispersion Parameters and Differential Pressure Fluctuations in a Column Flotation.}, journal = {ACS omega}, volume = {6}, number = {34}, pages = {21900-21908}, pmid = {34497885}, issn = {2470-1343}, abstract = {Flotation separation, which is the most important mineral beneficiation technique, is dependent on gas dispersion (hydrodynamic conditions). Thus, many investigations have focused on the precise determination of hydrodynamic conditions such as Reynolds number of the bubbles, bubble velocity, and bubble diameter. However, few studies have examined their relationships with pressure fluctuations in a column flotation. This study introduced the differential pressure fluctuations as an actual variable that could be considered to determine the collection zone's hydrodynamic conditions in a cyclonic microbubble flotation column. In general, the outcomes indicated that superficial gas velocity had the most substantial relationship with the differential pressure fluctuations among other flotation factors (such as pump speed, superficial gas velocity, superficial water velocity, and frother dosage). Furthermore, a high coefficient of determination (R [2] > 0.77) for the equation generated to assess the relationships demonstrated that differential pressure fluctuations could be used as a promising tool to determine the hydrodynamic parameters' characteristics in the flotation columns.}, } @article {pmid34497293, year = {2021}, author = {Aghamiri, H and Niknejadi, M and Toghraie, D}, title = {Analysis of the forced convection of two-phase Ferro-nanofluid flow in a completely porous microchannel containing rotating cylinders.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {17811}, pmid = {34497293}, issn = {2045-2322}, abstract = {In the present work, the forced convection of nanofluid flow in a microchannel containing rotating cylinders is investigated in different geometries. The heat flux applied to the microchannel wall is 10,000 W m[-2]. The effects of Reynolds number, the volume fraction of nanoparticles, and the porosity percentage of the porous medium are investigated on the flow fields, temperature, and heat transfer rate. Reynolds number values vary from Re = 250-1000, non-dimensional rotational velocities 1 and 2, respectively, and volume fraction of nanoparticles 0-2%. The results show that increasing the velocity of rotating cylinders increases the heat transfer; also, increasing the Reynolds number and volume fraction of nanoparticles increases the heat transfer, pressure drop, and Cf,ave. By comparing the porosity percentages with each other, it is concluded that due to the greater contact of the nanofluid with the porous medium and the creation of higher velocity gradients, the porosity percentage is 45% and the values of are 90% higher than the porosity percentage. Comparing porosity percentages with each other, at porosity percentage 90% is greater than at porosity percentage 45%. On the other hand, increasing the Reynolds number reduces the entropy generation due to heat transfer and increases the entropy generation due to friction. Increasing the volume fraction of nanoparticles increases the entropy generations due to heat transfer and friction.}, } @article {pmid34482836, year = {2021}, author = {Mandell, JG and Loke, YH and Mass, PN and Cleveland, V and Delaney, M and Opfermann, J and Aslan, S and Krieger, A and Hibino, N and Olivieri, LJ}, title = {Altered hemodynamics by 4D flow cardiovascular magnetic resonance predict exercise intolerance in repaired coarctation of the aorta: an in vitro study.}, journal = {Journal of cardiovascular magnetic resonance : official journal of the Society for Cardiovascular Magnetic Resonance}, volume = {23}, number = {1}, pages = {99}, pmid = {34482836}, issn = {1532-429X}, support = {R01 HL143468/HL/NHLBI NIH HHS/United States ; R38 AI140298/AI/NIAID NIH HHS/United States ; R38AI140298/AI/NIAID NIH HHS/United States ; R01HL143468-0/HL/NHLBI NIH HHS/United States ; }, mesh = {Aorta ; Aorta, Thoracic/diagnostic imaging/surgery ; *Aortic Coarctation/diagnostic imaging/surgery ; Blood Flow Velocity ; Hemodynamics ; Humans ; Magnetic Resonance Spectroscopy ; Predictive Value of Tests ; Retrospective Studies ; }, abstract = {BACKGROUND: Coarctation of the aorta (CoA) is associated with decreased exercise capacity despite successful repair. Altered flow patterns have been identified due to abnormal aortic arch geometry. Our previous work demonstrated aorta size mismatch to be associated with exercise intolerance in this population. In this study, we studied aortic flow patterns during simulations of exercise in repaired CoA using 4D flow cardiovascular magnetic resonance (CMR) using aortic replicas connected to an in vitro flow pump and correlated findings with exercise stress test results to identify biomarkers of exercise intolerance.

METHODS: Patients with CoA repair were retrospectively analyzed after CMR and exercise stress test. Each aorta was manually segmented and 3D printed. Pressure gradient measurements from ascending aorta (AAo) to descending aorta (DAo) and 4D flow CMR were performed during simulations of rest and exercise using a mock circulatory flow loop. Changes in wall shear stress (WSS) and secondary flow formation (vorticity and helicity) from rest to exercise were quantified, as well as estimated DAo Reynolds number. Parameters were correlated with percent predicted peak oxygen consumption (VO2max) and aorta size mismatch (DAAo/DDAo).

RESULTS: Fifteen patients were identified (VO2max 47 to 126% predicted). Pressure gradient did not correlate with VO2max at rest or exercise. VO2max correlated positively with the change in peak vorticity (R = 0.55, p = 0.03), peak helicity (R = 0.54, p = 0.04), peak WSS in the AAo (R = 0.68, p = 0.005) and negatively with peak WSS in the DAo (R = - 0.57, p = 0.03) from rest to exercise. DAAo/DDAo correlated strongly with change in vorticity (R = - 0.38, p = 0.01), helicity (R = - 0.66, p = 0.007), and WSS in the AAo (R = - 0.73, p = 0.002) and DAo (R = 0.58, p = 0.02). Estimated DAo Reynolds number negatively correlated with VO2max for exercise (R = - 0.59, p = 0.02), but not rest (R = - 0.28, p = 0.31). Visualization of streamline patterns demonstrated more secondary flow formation in aortic arches with better exercise capacity, larger DAo, and lower Reynolds number.

CONCLUSIONS: There are important associations between secondary flow characteristics and exercise capacity in repaired CoA that are not captured by traditional pressure gradient, likely due to increased turbulence and inefficient flow. These 4D flow CMR parameters are a target of investigation to identify optimal aortic arch geometry and improve long term clinical outcomes after CoA repair.}, } @article {pmid34455847, year = {2021}, author = {Simonis, S and Haussmann, M and Kronberg, L and Dörfler, W and Krause, MJ}, title = {Linear and brute force stability of orthogonal moment multiple-relaxation-time lattice Boltzmann methods applied to homogeneous isotropic turbulence.}, journal = {Philosophical transactions. Series A, Mathematical, physical, and engineering sciences}, volume = {379}, number = {2208}, pages = {20200405}, doi = {10.1098/rsta.2020.0405}, pmid = {34455847}, issn = {1471-2962}, abstract = {Multiple-relaxation-time (MRT) lattice Boltzmann methods (LBM) based on orthogonal moments exhibit lattice Mach number dependent instabilities in diffusive scaling. The present work renders an explicit formulation of stability sets for orthogonal moment MRT LBM. The stability sets are defined via the spectral radius of linearized amplification matrices of the MRT collision operator with variable relaxation frequencies. Numerical investigations are carried out for the three-dimensional Taylor-Green vortex benchmark at Reynolds number 1600. Extensive brute force computations of specific relaxation frequency ranges for the full test case are opposed to the von Neumann stability set prediction. Based on that, we prove numerically that a scan over the full wave space, including scaled mean flow variations, is required to draw conclusions on the overall stability of LBM in turbulent flow simulations. Furthermore, the von Neumann results show that a grid dependence is hardly possible to include in the notion of linear stability for LBM. Lastly, via brute force stability investigations based on empirical data from a total number of 22 696 simulations, the existence of a deterministic influence of the grid resolution is deduced. This article is part of the theme issue 'Progress in mesoscale methods for fluid dynamics simulation'.}, } @article {pmid34455509, year = {2021}, author = {Ali, A and Jana, RN and Das, S}, title = {Significance of entropy generation and heat source: the case of peristaltic blood flow through a ciliated tube conveying Cu-Ag nanoparticles using Phan-Thien-Tanner model.}, journal = {Biomechanics and modeling in mechanobiology}, volume = {20}, number = {6}, pages = {2393-2412}, pmid = {34455509}, issn = {1617-7940}, mesh = {Copper/*chemistry ; *Entropy ; *Hot Temperature ; Metal Nanoparticles/*chemistry ; *Models, Biological ; Peristalsis/*physiology ; Pressure ; Reproducibility of Results ; Silver/*chemistry ; }, abstract = {The present speculative investigation is concentrated to analyze the entropy generation and heat transfer phenomena in ciliary induced peristalsis of blood with the suspension of hybrid nanoparticles in a tube with heat source impact. The blood is assumed to contain copper (Cu) and silver (Ag) nanoparticles (NPs). The ciliary inner wall of the tube has been considered with small hair-like structures. The Phan-Thien-Tanner (PTT) fluid model is employed to describe the non-Newtonian rheological characteristics of blood. The conservative equations are normalized and simplified by utilizing scaling analysis with the assumption of low Reynolds number and large wavelength approximations. The analytical inspection exposes that the total entropy generation gets a decrement for mounting values of cilia length, while reversed impact is detected for an increment in heat source parameter. Hybrid nano-blood exhibits a greater total entropy number than mono nano-blood. This research study may be beneficial to medical experts and researchers in the field of embryology. Cysts in the ciliated fallopian tube, where embryos develop, are removed by using nanoparticles (nano-drug delivery).}, } @article {pmid34442509, year = {2021}, author = {Parveen, N and Awais, M and Awan, SE and Khan, WU and He, Y and Malik, MY}, title = {Entropy Generation Analysis and Radiated Heat Transfer in MHD (Al2O3-Cu/Water) Hybrid Nanofluid Flow.}, journal = {Micromachines}, volume = {12}, number = {8}, pages = {}, pmid = {34442509}, issn = {2072-666X}, abstract = {This research concerns the heat transfer and entropy generation analysis in the MHD axisymmetric flow of Al2O3-Cu/H2O hybrid nanofluid. The magnetic induction effect is considered for large magnetic Reynolds number. The influences of thermal radiations, viscous dissipation and convective temperature conditions over flow are studied. The problem is modeled using boundary layer theory, Maxwell's equations and Fourier's conduction law along with defined physical factors. Similarity transformations are utilized for model simplification which is analytically solved with the homotopy analysis method. The h-curves up to 20th order for solutions establishes the stability and convergence of the adopted computational method. Rheological impacts of involved parameters on flow variables and entropy generation number are demonstrated via graphs and tables. The study reveals that entropy in system of hybrid nanofluid affected by magnetic induction declines for β while it enhances for Bi, R and λ. Moreover, heat transfer rate elevates for large Bi with convective conditions at surface.}, } @article {pmid34441209, year = {2021}, author = {Ahammad, NA and Badruddin, IA and Kamangar, S and Khaleed, HMT and Saleel, CA and Mahlia, TMI}, title = {Heat Transfer and Entropy in a Vertical Porous Plate Subjected to Suction Velocity and MHD.}, journal = {Entropy (Basel, Switzerland)}, volume = {23}, number = {8}, pages = {}, pmid = {34441209}, issn = {1099-4300}, support = {RGP.1/327/42//Deanship of Scientific Research at King Khalid University/ ; }, abstract = {This article presents an investigation of heat transfer in a porous medium adjacent to a vertical plate. The porous medium is subjected to a magnetohydrodynamic effect and suction velocity. The governing equations are nondepersonalized and converted into ordinary differential equations. The resulting equations are solved with the help of the finite difference method. The impact of various parameters, such as the Prandtl number, Grashof number, permeability parameter, radiation parameter, Eckert number, viscous dissipation parameter, and magnetic parameter, on fluid flow characteristics inside the porous medium is discussed. Entropy generation in the medium is analyzed with respect to various parameters, including the Brinkman number and Reynolds number. It is noted that the velocity profile decreases in magnitude with respect to the Prandtl number, but increases with the radiation parameter. The Eckert number has a marginal effect on the velocity profile. An increased radiation effect leads to a reduced thermal gradient at the hot surface.}, } @article {pmid34432464, year = {2021}, author = {Gu, R and Lehn, JM}, title = {Constitutional Dynamic Selection at Low Reynolds Number in a Triple Dynamic System: Covalent Dynamic Adaptation Driven by Double Supramolecular Self-Assembly.}, journal = {Journal of the American Chemical Society}, volume = {143}, number = {35}, pages = {14136-14146}, doi = {10.1021/jacs.1c04446}, pmid = {34432464}, issn = {1520-5126}, abstract = {A triple dynamic complex system has been designed, implementing a dynamic covalent process coupled to two supramolecular self-assembly steps. To this end, two dynamic covalent libraries (DCLs), DCL-1 and DCL-2, have been established on the basis of dynamic covalent C═C/C═N organo-metathesis between two Knoevenagel derivatives and two imines. Each DCL contains a barbituric acid-based Knoevenagel constituent that may undergo a sequential double self-organization process involving first the formation of hydrogen-bonded hexameric supramolecular macrocycles that subsequently undergo stacking to generate a supramolecular polymer SP yielding a viscous gel state. Both DCLs display selective self-organization-driven amplification of the constituent that leads to the SP. Dissociation of the SP on heating causes reversible randomization of the constituent distributions of the DCLs as a function of temperature. Furthermore, diverse distribution patterns of DCL-2 were induced by modulation of temperature and solvent composition. The present dynamic systems display remarkable self-organization-driven constitutional adaption and tunable composition by coupling between dynamic covalent component selection and two-stage supramolecular organization. In more general terms, they reveal dynamic adaptation by component selection in low Reynolds number conditions of living systems where frictional effects dominate inertial behavior.}, } @article {pmid34410363, year = {2021}, author = {Herrera-Amaya, A and Seber, EK and Murphy, DW and Patry, WL and Knowles, TS and Bubel, MM and Maas, AE and Byron, ML}, title = {Spatiotemporal Asymmetry in Metachronal Rowing at Intermediate Reynolds Numbers.}, journal = {Integrative and comparative biology}, volume = {61}, number = {5}, pages = {1579-1593}, doi = {10.1093/icb/icab179}, pmid = {34410363}, issn = {1557-7023}, mesh = {Animals ; Biomechanical Phenomena ; Body Size ; *Extremities ; Models, Theoretical ; *Swimming ; }, abstract = {In drag-based swimming, individual propulsors operating at low Reynolds numbers (where viscous forces dominate over inertial forces) must execute a spatially asymmetric stroke to produce net fluid displacement. Temporal asymmetry (that is, differing duration between the power vs. recovery stroke) does not affect the overall generated thrust in this time-reversible regime. Metachronal rowing, in which multiple appendages beat sequentially, is used by a wide variety of organisms from low to intermediate Reynolds numbers. At the upper end of this range, inertia becomes important, and increasing temporal asymmetry can be an effective way to increase thrust. However, the combined effects of spatial and temporal asymmetry are not fully understood in the context of metachronal rowing. To explore the role of spatiotemporal asymmetry in metachronal rowing, we combine laboratory experiments and reduced-order analytical modeling. We measure beat kinematics and generated flows in two species of lobate ctenophores across a range of body sizes, from 7 to 40 mm in length. We observe characteristically different flows in ctenophores of differing body size and Reynolds number, and a general decrease in spatial asymmetry and increase in temporal asymmetry with increasing Reynolds number. We also construct a one-dimensional mathematical model consisting of a row of oscillating flat plates whose flow-normal areas change with time, and use it to explore the propulsive forces generated across a range of Reynolds numbers and kinematic parameters. The model results show that while both types of asymmetry increase force production, they have different effects in different regions of the parameter space. These results may have strong biological implications, as temporal asymmetry can be actively controlled while spatial asymmetry is likely to be partially or entirely driven by passive fluid-structure interaction.}, } @article {pmid34391375, year = {2022}, author = {Pattnaik, PK and Abbas, MA and Mishra, S and Khan, SU and Bhatti, MM}, title = {Free Convective Flow of Hamilton-Crosser Model Gold-water Nanofluid Through a Channel with Permeable Moving Walls.}, journal = {Combinatorial chemistry & high throughput screening}, volume = {25}, number = {7}, pages = {1103-1114}, doi = {10.2174/1386207324666210813112323}, pmid = {34391375}, issn = {1875-5402}, mesh = {Computer Simulation ; Gold ; Hot Temperature ; *Metal Nanoparticles ; *Water ; }, abstract = {BACKGROUND: The present manuscript analyzes the influence of buoyant forces of a conducting time-dependent nanofluid flow through porous moving walls. The medium is also filled with porous materials. In addition to that, uniform heat source and absorption parameters are considered that affect the nanofluid model.

INTRODUCTION: The model is based on the thermophysical properties of Hamilton-Crosser's nanofluid model, in which a gold nanoparticle is submerged into the base fluid water. Before simulation is obtained by a numerical method, suitable transformation is used to convert nonlinear coupled PDEs to ODEs.

METHOD: Runge-Kutta's fourth-order scheme is applied successfully for the first-order ODEs in conjunction with the shooting technique.

RESULT: Computations for the coefficients of rate constants are presented through graphs, along with the behavior of several physical parameters augmented by the flow phenomena.

CONCLUSION: The present investigation may be compatible with the applications of biotechnology. It is seen that the inclusion of volume concentration and the fluid velocity enhances near the middle layer of the channel and retards near the permeable walls. Also, augmented values of the Reynolds number and both cooling and heating of the wall increase the rate of shear stress.}, } @article {pmid34384065, year = {2021}, author = {Luo, Y and Wright, M and Xiao, Q and Yue, H and Pan, G}, title = {Fluid-structure interaction analysis on motion control of a self-propelled flexible plate near a rigid body utilizing PD control.}, journal = {Bioinspiration & biomimetics}, volume = {16}, number = {6}, pages = {}, doi = {10.1088/1748-3190/ac1cee}, pmid = {34384065}, issn = {1748-3190}, mesh = {Animals ; Biomechanical Phenomena ; Fishes ; *Models, Biological ; Motion ; *Swimming ; }, abstract = {Inspired by a previous experimental study of fish swimming near a cylinder, we numerically investigate the swimming and station-holding behavior of a flexible plate ahead of a circular cylinder whose motion is controlled by a proportional-derivative (PD) controller. Specifically, the deformation of this two-dimensional plate is actuated by a periodically varying external force applied on the body surface, which mimics the fish muscle force to produce propulsive thrust. The actuation force amplitude is dynamically adjusted by a feedback controller to instruct the plate to swim the desired distance from an initial position to a target location and then hold the station there. Instead of directly using the instantaneous position signal, an average speed measured over one force actuation period is proposed with the inclusion of instantaneous position information to form the tracking error for the PD control. Our results show that the motion control of swimming and station holding has been achieved by this simple but effective feedback control without large overshoot when approaching the target at different flow conditions and actuation force formulas. Although the swimming distance remains the same, a plate whose initial position is closer to the cylinder requires less energy expenditure to swim to the target location and hold the station there. This is because the low-pressure zone near the trailing edge of the plate is reduced in size, which provides drag reduction, contributing to reduced swimming energy. A higher Reynolds number also leads to energy savings. Under the same control strategy, the swimming performance is more affected by the force-frequency while the phase shift of the actuation force has a less significant impact.}, } @article {pmid34381068, year = {2021}, author = {Lin, P and Liu, X and Xiong, N and Wang, X and Shang, M and Liu, G and Tao, Y}, title = {Numerical study on the influence of wall temperature gradient on aerodynamic characteristics of low aspect ratio flying wing configuration.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {16295}, pmid = {34381068}, issn = {2045-2322}, abstract = {With the aim for a low-aspect-ratio flying wing configuration, this study explores the influence of wall temperature gradient on the laminar and turbulent boundary layers of aircraft surface and determines the effect on the transition Reynolds number and wall friction drag. A four-equation turbulence model with transition mode is used to numerically simulate the flow around the model. The variation of wall friction coefficient, transition Reynolds number, and turbulent boundary layer flow with wall temperature are emphatically investigated. Results show that when the wall temperature increases from 288 to 500 K, the boundary layer transition Reynolds number for the wing section increased by approximately 28% and the surface friction drags decreases by approximately 10.7%. The hot wall enhances the viscous effects of the laminar temperature boundary layer, reduces the Reynolds shear stress and turbulent kinetic energy, and increases the flow stability. However, the velocity gradient and shear stress in the bottom of the turbulent boundary layer decreases, which leads to reduced friction shear stress on the wall surface. Therefore, for the low-aspect-ratio flying wing model, the hot wall can delay the boundary layer transition and reduce the friction drag coefficient in the turbulent region.}, } @article {pmid34373556, year = {2021}, author = {Xia, WF and Hafeez, MU and Khan, MI and Shah, NA and Chung, JD}, title = {Entropy optimized dissipative flow of hybrid nanofluid in the presence of non-linear thermal radiation and Joule heating.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {16067}, pmid = {34373556}, issn = {2045-2322}, abstract = {Present article reads three dimensional flow analysis of incompressible viscous hybrid nanofluid in a rotating frame. Ethylene glycol is used as a base liquid while nanoparticles are of copper and silver. Fluid is bounded between two parallel surfaces in which the lower surface stretches linearly. Fluid is conducting hence uniform magnetic field is applied. Effects of non-linear thermal radiation, Joule heating and viscous dissipation are entertained. Interesting quantities namely surface drag force and Nusselt number are discussed. Rate of entropy generation is examined. Bvp4c numerical scheme is used for the solution of transformed O.D.Es. Results regarding various flow parameters are obtained via bvp4c technique in MATLAB Software version 2019, and displayed through different plots. Our obtained results presents that velocity field decreases with respect to higher values of magnetic parameter, Reynolds number and rotation parameter. It is also observed that the temperature field boots subject to radiation parameter. Results are compared with Ishak et al. (Nonlinear Anal R World Appl 10:2909-2913, 2009) and found very good agreement with them. This agreement shows that the results are 99.99% match with each other.}, } @article {pmid34373493, year = {2021}, author = {Alihosseini, Y and Azaddel, MR and Moslemi, S and Mohammadi, M and Pormohammad, A and Targhi, MZ and Heyhat, MM}, title = {Effect of liquid cooling on PCR performance with the parametric study of cross-section shapes of microchannels.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {16072}, pmid = {34373493}, issn = {2045-2322}, abstract = {In recent years, PCR-based methods as a rapid and high accurate technique in the industry and medical fields have been expanded rapidly. Where we are faced with the COVID-19 pandemic, the necessity of a rapid diagnosis has felt more than ever. In the current interdisciplinary study, we have proposed, developed, and characterized a state-of-the-art liquid cooling design to accelerate the PCR procedure. A numerical simulation approach is utilized to evaluate 15 different cross-sections of the microchannel heat sink and select the best shape to achieve this goal. Also, crucial heat sink parameters are characterized, e.g., heat transfer coefficient, pressure drop, performance evaluation criteria, and fluid flow. The achieved result showed that the circular cross-section is the most efficient shape for the microchannel heat sink, which has a maximum heat transfer enhancement of 25% compared to the square shape at the Reynolds number of 1150. In the next phase of the study, the circular cross-section microchannel is located below the PCR device to evaluate the cooling rate of the PCR. Also, the results demonstrate that it takes 16.5 s to cool saliva samples in the PCR well, which saves up to 157.5 s for the whole amplification procedure compared to the conventional air fans. Another advantage of using the microchannel heat sink is that it takes up a little space compared to other common cooling methods.}, } @article {pmid34372345, year = {2021}, author = {Costantini, M and Henne, U and Klein, C and Miozzi, M}, title = {Skin-Friction-Based Identification of the Critical Lines in a Transonic, High Reynolds Number Flow via Temperature-Sensitive Paint.}, journal = {Sensors (Basel, Switzerland)}, volume = {21}, number = {15}, pages = {}, pmid = {34372345}, issn = {1424-8220}, abstract = {In this contribution, three methodologies based on temperature-sensitive paint (TSP) data were further developed and applied for the optical determination of the critical locations of flow separation and reattachment in compressible, high Reynolds number flows. The methodologies rely on skin-friction extraction approaches developed for low-speed flows, which were adapted in this work to study flow separation and reattachment in the presence of shock-wave/boundary-layer interaction. In a first approach, skin-friction topological maps were obtained from time-averaged surface temperature distributions, thus enabling the identification of the critical lines as converging and diverging skin-friction lines. In the other two approaches, the critical lines were identified from the maps of the propagation celerity of temperature perturbations, which were determined from time-resolved TSP data. The experiments were conducted at a freestream Mach number of 0.72 and a chord Reynolds number of 9.7 million in the Transonic Wind Tunnel Göttingen on a VA-2 supercritical airfoil model, which was equipped with two exchangeable TSP modules specifically designed for transonic, high Reynolds number tests. The separation and reattachment lines identified via the three different TSP-based approaches were shown to be in mutual agreement, and were also found to be in agreement with reference experimental and numerical data.}, } @article {pmid34359055, year = {2021}, author = {Diaz, K and Robinson, TL and Aydin, YO and Aydin, E and Goldman, DI and Wan, KY}, title = {A minimal robophysical model of quadriflagellate self-propulsion.}, journal = {Bioinspiration & biomimetics}, volume = {16}, number = {6}, pages = {}, doi = {10.1088/1748-3190/ac1b6e}, pmid = {34359055}, issn = {1748-3190}, mesh = {Flagella ; Gait ; Locomotion ; *Robotics ; *Swimming ; }, abstract = {Locomotion at the microscale is remarkably sophisticated. Microorganisms have evolved diverse strategies to move within highly viscous environments, using deformable, propulsion-generating appendages such as cilia and flagella to drive helical or undulatory motion. In single-celled algae, these appendages can be arranged in different ways around an approximately 10 μm long cell body, and coordinated in distinct temporal patterns. Inspired by the observation that some quadriflagellates (bearing four flagella) have an outwardly similar morphology and flagellar beat pattern, yet swim at different speeds, this study seeks to determine whether variations in swimming performance could arise solely from differences in swimming gait. Robotics approaches are particularly suited to such investigations, where the phase relationships between appendages can be readily manipulated. Here, we developed autonomous, algae-inspired robophysical models that can self-propel in a viscous fluid. These macroscopic robots (length and width = 8.5 cm, height = 2 cm) have four independently actuated 'flagella' (length = 13 cm) that oscillate under low-Reynolds number conditions (Re∼O(10-1)). We tested the swimming performance of these robot models with appendages arranged two distinct configurations, and coordinated in three distinct gaits. The gaits, namely the pronk, the trot, and the gallop, correspond to gaits adopted by distinct microalgal species. When the appendages are inserted perpendicularly around a central 'body', the robot achieved a net performance of 0.15-0.63 body lengths per cycle, with the trot gait being the fastest. Robotic swimming performance was found to be comparable to that of the algal microswimmers across all gaits. By creating a minimal robot that can successfully reproduce cilia-inspired drag-based swimming, our work paves the way for the design of next-generation devices that have the capacity to autonomously navigate aqueous environments.}, } @article {pmid34357216, year = {2021}, author = {Li, L and Chen, Q and Sui, G and Qian, J and Tsai, CT and Cheng, X and Jing, W}, title = {A Three-Dimensional Micromixer Using Oblique Embedded Ridges.}, journal = {Micromachines}, volume = {12}, number = {7}, pages = {}, pmid = {34357216}, issn = {2072-666X}, abstract = {A micromixer is one of the most significant components in a microfluidic system. A three-dimensional micromixer was developed with advantages of high efficiency, simple fabrication, easy integration, and ease of mass production. The designed principle is based on the concepts of splitting-recombination and chaotic advection. A numerical model of this micromixer was established to characterize the mixing performance for different parameters. A critical Reynolds number (Re) was obtained from the simulation results. When the Re number is smaller than the critical value, the fluid mixing is mainly dependent on the mechanism of splitting-recombination, therefore, the length of the channel capable of complete mixing (complete mixing length) increases as the Re number increases. When the Re number is larger than the critical value, the fluid mixing is dominated by chaotic advection, and the complete mixing length decreases as the Re number increases. For normal fluids, a complete mixing length of 500 µm can be achieved at a very small Re number of 0.007 and increases to 2400 µm as the Re number increases to the critical value of 4.7. As the Re number keep increasing and passes the critical Re number, the complete mixing length continues to descend to 650 µm at the Re number of 66.7. For hard-to-mix fluids (generally referring to fluids with high viscosity and low diffusion coefficient, which are difficult to mix), even though no evidence of strong chaotic advection is presented in the simulation, the micromixer can still achieve a complete mixing length of 2550 µm. The mixing performance of the micromixer was also verified by experiments. The experimental results showed a consistent trend with the numerical simulation results, which both climb upward when the Re number is around 0.007 (flow rate of 0.03 μm/min) to around 10 (flow rate of 50 μm/min), then descend when the Re number is around 13.3 (flow rate of 60 µm/min).}, } @article {pmid34357184, year = {2021}, author = {Nichka, VS and Nikonenko, VV and Bazinet, L}, title = {Fouling Mitigation by Optimizing Flow Rate and Pulsed Electric Field during Bipolar Membrane Electroacidification of Caseinate Solution.}, journal = {Membranes}, volume = {11}, number = {7}, pages = {}, pmid = {34357184}, issn = {2077-0375}, support = {19-38-90256//Russian Foundation for Basic Research/ ; 210829409//Natural Sciences and Engineering Research Council of Canada/ ; }, abstract = {The efficiency of separation processes using ion exchange membranes (IEMs), especially in the food industry, is significantly limited by the fouling phenomenon, which is the process of the attachment and growth of certain species on the surface and inside the membrane. Pulsed electric field (PEF) mode, which consists in the application of constant current density pulses during a fixed time (Ton) alternated with pause lapses (Toff), has a positive antifouling impact. The aim of this study was to investigate the combined effect of three different relatively high flow rates of feed solution (corresponding to Reynolds numbers of 187, 374 and 560) and various pulse-pause ratios of PEF current regime on protein fouling kinetics during electrodialysis with bipolar membranes (EDBM) of a model caseinate solution. Four different pulse/pause regimes (with Ton/Toff ratios equal to 10 s/10 s, 10 s/20 s, 10 s/33 s and 10 s/50 s) during electrodialysis (ED) treatment were evaluated at a current density of 5 mA/cm[2]. It was found that increasing the pause duration and caseinate solution flow rate had a positive impact on the minimization of protein fouling occurring on the cationic surface of the bipolar membrane (BPM) during the EDBM. Both a long pause and high flow rate contribute to a more effective decrease in the concentration of protons and caseinate anions at the BPM surface: a very good membrane performance was achieved with 50 s of pause duration of PEF and a flow rate corresponding to Re = 374. A further increase in PEF pause duration (above 50 s) or flow rate (above Re = 374) did not lead to a significant decrease in the amount of fouling.}, } @article {pmid34349343, year = {2021}, author = {Ferroni, C and Bracconi, M and Ambrosetti, M and Maestri, M and Groppi, G and Tronconi, E}, title = {A Fundamental Investigation of Gas/Solid Heat and Mass Transfer in Structured Catalysts Based on Periodic Open Cellular Structures (POCS).}, journal = {Industrial & engineering chemistry research}, volume = {60}, number = {29}, pages = {10522-10538}, pmid = {34349343}, issn = {0888-5885}, abstract = {In this work, we investigate the gas-solid heat and mass transfer in catalytically activated periodic open cellular structures, which are considered a promising solution for intensification of catalytic processes limited by external transport, aiming at the derivation of suitable correlations. Computational fluid dynamics is employed to investigate the Tetrakaidekahedral and Diamond lattice structures. The influence of the morphological features and flow conditions on the external transport properties is assessed. The strut diameter is an adequate characteristic length for the formulation of heat and mass transfer correlations; accordingly, a power-law dependence of the Sherwood number to the Reynolds number between 0.33 and 0.67 was found according to the flow regimes in the range 1-128 of the Reynolds number. An additional -1.5-order dependence on the porosity is found. The formulated correlations are in good agreement with the simulation results and allow for the accurate evaluation of the external transfer coefficients for POCS.}, } @article {pmid34335006, year = {2021}, author = {Liu, K and Allahyari, M and Salinas, J and Zgheib, N and Balachandar, S}, title = {Investigation of theoretical scaling laws using large eddy simulations for airborne spreading of viral contagion from sneezing and coughing.}, journal = {Physics of fluids (Woodbury, N.Y. : 1994)}, volume = {33}, number = {6}, pages = {063318}, pmid = {34335006}, issn = {1070-6631}, abstract = {Using a set of large eddy point-particle simulations, we explore the fluid dynamics of an ejected puff resulting from a cough/sneeze. The ejection contains over 61 000 potentially virus-laden droplets at an injection Reynolds number of about 46 000, comparable to an actual cough/sneeze. We observe that global puff properties, such as centroid, puff volume, momentum, and buoyancy vary little across realizations. Other properties, such as maximum extent, shape, and edge velocity of the puff, may exhibit substantial variation. In many realizations, a portion of the puff splits off and advances along a random direction, while keeping airborne droplet nuclei afloat. This peeled-off portion provides a mechanism for virus-laden droplets to travel over large distances in a short amount of time. We also observe that the vast majority of droplets remain suspended within the puff after all liquid has evaporated. The main objectives of the study are to (i) evaluate assumptions of Balachandar's et al. theory [Int. J. Multiphase Flow 132, 103439 (2020)], which include buoyancy effects, shape of the puff, and droplet evaporation rate, (ii) obtain values of closure parameters, which include location and time of the virtual origin, and puff entrainment and drag coefficients, and (iii) evaluate the accuracy of the theory in predicting the shape, size, and location of the puff, as well as droplet number density long after ejection. The theory adequately predicts global puff properties including size, velocity, and distance traveled, the largest size of droplets that exit the puff due to settling, and the droplet size distribution within the puff long after ejection.}, } @article {pmid34319753, year = {2021}, author = {Singh, RK and Mahato, LK and Mandal, DK}, title = {Airflow-Assisted Impact of Drops of Various Viscosities: The Role of Viscous Dissipation, Normal Imposed Pressure, and Shear Flow of Air.}, journal = {Langmuir : the ACS journal of surfaces and colloids}, volume = {37}, number = {31}, pages = {9504-9517}, doi = {10.1021/acs.langmuir.1c01367}, pmid = {34319753}, issn = {1520-5827}, abstract = {The role of liquid viscosity on the spreading for an airflow-assisted impact of drops on a surface is investigated. The spreading diameter is found to increase with the Reynolds number of the airflow (Reair) for a given viscosity and impact Weber number (We) compared to the still air. The increment is higher at a low We for viscous drops, whereas the effect of Reair dominates at the intermediate We as the viscosity decreases. Two extra forces, the normal imposed pressure and shear force of air, act on the drop and influence the spreading along with the viscous dissipation. The drop's curvature decreases depending on the viscosity and impact velocity while spreading. Large-scale eddies near the drop-surface region are observed due to the separation of the incident airflow. The formation of eddies signifies low-pressure zones, which extract the trapped air, causing the spreading diameter of the viscous drop to increase at a low We. With the increase in the We, the lamella thickness of low-viscosity drops decreases and is pushed out by the air shear causing the spreading factor to increase. The boundary layer thickness is estimated using the energy balance method to predict the maximum spreading factor. The prediction compares well with the experimental one for higher viscosities. The accuracy improves when the effect of low pressure is incorporated. To confirm, the experimental spreading is compared with that obtained from three existing models, and one, which considers the influence, is observed to provide a better prediction.}, } @article {pmid34297252, year = {2021}, author = {Sharifi, A and Gendernalik, A and Garrity, D and Bark, D}, title = {Valveless pumping behavior of the simulated embryonic heart tube as a function of contractile patterns and myocardial stiffness.}, journal = {Biomechanics and modeling in mechanobiology}, volume = {20}, number = {5}, pages = {2001-2012}, pmid = {34297252}, issn = {1617-7940}, mesh = {Animals ; Biomechanical Phenomena ; Cardiac Output ; Computer Simulation ; Electric Impedance ; Heart/*embryology/*physiology ; Heart Rate ; *Hemodynamics ; Models, Cardiovascular ; Models, Theoretical ; *Myocardial Contraction ; Myocardium/*pathology ; Peristalsis ; Pressure ; Stress, Mechanical ; Zebrafish/*embryology ; }, abstract = {During development, the heart begins pumping as a valveless multilayered tube capable of driving blood flow throughout the embryonic vasculature. The mechanical properties and how they interface with pumping function are not well-defined at this stage. Here, we evaluate pumping patterns using a fluid-structure interaction computational model, combined with experimental data and an energetic analysis to investigate myocardial mechanical properties. Through this work, we propose that a myocardium modeled as a Neo-Hookean material with a material constant on the order of 10 kPa is necessary for the heart tube to function with an optimal pressure and cardiac output.}, } @article {pmid34293964, year = {2021}, author = {Akram, S and Athar, M and Saeed, K and Razia, A}, title = {Crossbreed impact of double-diffusivity convection on peristaltic pumping of magneto Sisko nanofluids in non-uniform inclined channel: A bio-nanoengineering model.}, journal = {Science progress}, volume = {104}, number = {3}, pages = {368504211033677}, doi = {10.1177/00368504211033677}, pmid = {34293964}, issn = {2047-7163}, abstract = {The consequences of double-diffusivity convection on the peristaltic transport of Sisko nanofluids in the non-uniform inclined channel and induced magnetic field are discussed in this article. The mathematical modeling of Sisko nanofluids with induced magnetic field and double-diffusivity convection is given. To simplify PDEs that are highly nonlinear in nature, the low but finite Reynolds number, and long wavelength estimation are used. The Numerical solution is calculated for the non-linear PDEs. The exact solution of concentration, temperature and nanoparticle are obtained. The effect of various physical parameters of flow quantities is shown in numerical and graphical data. The outcomes show that as the thermophoresis and Dufour parameters are raised, the profiles of temperature, concentration, and nanoparticle fraction all significantly increase.}, } @article {pmid34286832, year = {2021}, author = {Kasoju, VT and Moen, DS and Ford, MP and Ngo, TT and Santhanakrishnan, A}, title = {Interspecific variation in bristle number on forewings of tiny insects does not influence clap-and-fling aerodynamics.}, journal = {The Journal of experimental biology}, volume = {224}, number = {18}, pages = {}, doi = {10.1242/jeb.239798}, pmid = {34286832}, issn = {1477-9145}, mesh = {Animals ; Biomechanical Phenomena ; *Flight, Animal ; Insecta ; Models, Biological ; Phylogeny ; *Wings, Animal ; }, abstract = {Miniature insects must overcome significant viscous resistance in order to fly. They typically possess wings with long bristles on the fringes and use a clap-and-fling mechanism to augment lift. These unique solutions to the extreme conditions of flight at tiny sizes (<2 mm body length) suggest that natural selection has optimized wing design for better aerodynamic performance. However, species vary in wingspan, number of bristles (n) and bristle gap (G) to diameter (D) ratio (G/D). How this variation relates to body length (BL) and its effects on aerodynamics remain unknown. We measured forewing images of 38 species of thrips and 21 species of fairyflies. Our phylogenetic comparative analyses showed that n and wingspan scaled positively and similarly with BL across both groups, whereas G/D decreased with BL, with a sharper decline in thrips. We next measured aerodynamic forces and visualized flow on physical models of bristled wings performing clap-and-fling kinematics at a chord-based Reynolds number of 10 using a dynamically scaled robotic platform. We examined the effects of dimensional (G, D, wingspan) and non-dimensional (n, G/D) geometric variables on dimensionless lift and drag. We found that: (1) increasing G reduced drag more than decreasing D; (2) changing n had minimal impact on lift generation; and (3) varying G/D minimally affected aerodynamic forces. These aerodynamic results suggest little pressure to functionally optimize n and G/D. Combined with the scaling relationships between wing variables and BL, much wing variation in tiny flying insects might be best explained by underlying shared growth factors.}, } @article {pmid34283850, year = {2021}, author = {Dvoriashyna, M and Lauga, E}, title = {Hydrodynamics and direction change of tumbling bacteria.}, journal = {PloS one}, volume = {16}, number = {7}, pages = {e0254551}, pmid = {34283850}, issn = {1932-6203}, mesh = {Biomechanical Phenomena ; Escherichia coli/chemistry/*physiology ; Flagella/*physiology ; *Hydrodynamics ; Models, Biological ; Movement/*physiology ; Rotation ; Swimming/physiology ; }, abstract = {The bacterium Escherichia coli (E. coli) swims in viscous fluids by rotating several helical flagellar filaments, which are gathered in a bundle behind the cell during 'runs' wherein the cell moves steadily forward. In between runs, the cell undergoes quick 'tumble' events, during which at least one flagellum reverses its rotation direction and separates from the bundle, resulting in erratic motion in place and a random reorientation of the cell. Alternating between runs and tumbles allows cells to sample space by stochastically changing their propulsion direction after each tumble. The change of direction during a tumble is not uniformly distributed but is skewed towards smaller angles with an average of about 62°-68°, as first measured by Berg and Brown (1972). Here we develop a theoretical approach to model the angular distribution of swimming E. coli cells during tumbles. We first use past experimental imaging results to construct a kinematic description of the dynamics of the flagellar filaments during a tumble. We then employ low-Reynolds number hydrodynamics to compute the consequences of the kinematic model on the force and torque balance of the cell and to deduce the overall change in orientation. The results of our model are in good agreement with experimental observations. We find that the main change of direction occurs during the 'bundling' part of the process wherein, at the end of a tumble, the dispersed flagellar filaments are brought back together in the helical bundle, which we confirm using a simplified forced-sphere model.}, } @article {pmid34282226, year = {2021}, author = {Ishak, MS and Alsabery, AI and Hashim, I and Chamkha, AJ}, title = {Entropy production and mixed convection within trapezoidal cavity having nanofluids and localised solid cylinder.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {14700}, pmid = {34282226}, issn = {2045-2322}, support = {FRGS/1/2019/STG06/UKM/01/2//Malaysian Ministry of Education/ ; FRGS/1/2019/STG06/UKM/01/2//Malaysian Ministry of Education/ ; }, abstract = {The entropy production and mixed convection within a trapezoidal nanofluid-filled cavity having a localised solid cylinder is numerically examined using the finite element technique. The top horizontal surface moving at a uniform velocity is kept at a cold temperature, while the bottom horizontal surface is thermally activated. The remaining surfaces are maintained adiabatic. Water-based nanofluids ([Formula: see text] nanoparticles) are used in this study, and the Boussinesq approximation applies. The influence of the Reynolds number, Richardson number, nanoparticles volume fraction, dimensionless radius and location of the solid cylinder on the streamlines, isotherms and isentropic are examined. The results show that the solid cylinder's size and location are significant control parameters for optimising the heat transfer and the Bejan number inside the trapezoidal cavity. Furthermore, the maximum average Nusselt numbers are obtained for high R values, where the average Nusselt number is increased by 30% when R is raised from 0 to 0.25.}, } @article {pmid34275183, year = {2021}, author = {Gurovich, AN and Rodriguez, L and Morales-Acuna, F}, title = {There are no differences in brachial artery endothelial shear stress and blood flow patterns between males and females during exercise.}, journal = {Clinical physiology and functional imaging}, volume = {41}, number = {6}, pages = {471-479}, doi = {10.1111/cpf.12722}, pmid = {34275183}, issn = {1475-097X}, mesh = {*Brachial Artery/diagnostic imaging ; Cross-Sectional Studies ; *Endothelium, Vascular ; Exercise ; Female ; Hemodynamics ; Humans ; Male ; Regional Blood Flow ; Vasodilation ; }, abstract = {Premenopausal females have a lower cardiovascular risk than males. Sex differences on exercise-induced endothelial shear stress (ESS) and blood flow patterns may explain part of this risk reduction. The purpose of this cross-sectional study was to determine the differences in brachial artery exercise-induced ESS and blood flow patterns between males and females. Thirty subjects (13 females) were recruited to perform a three-workload steady-state exercise test based on blood lactate levels (i.e. <2.0, 2.0-4.0, >4.0 mmol/l). ESS and blood flow patterns were estimated at rest and during each workload using Womersley's approximation and Reynolds number, respectively. Both males and females showed an exercise intensity-dependent increase in antegrade and retrograde ESS. There was no significant sex effect or interaction for antegrade ESS (F(1, 30) = 0.715, p = 0.405 and F(1·672, 60) = 1.511, p = 0.232, respectively) or retrograde ESS (F(1, 30) = 0.794, p = 0.380 and F(1·810, 60) = 1.022, p = 0.361, respectively). Additionally, antegrade blood flow was turbulent during all bouts of exercise while retrograde blood flow became disturbed at moderate and high exercise intensities in both groups. There are no differences in exercise-induced ESS and blood flow patterns between males and females when the exercise load is equivalent. This suggests that the vascular benefits of exercise training are similar in both sexes from a haemodynamic standpoint.}, } @article {pmid34272432, year = {2021}, author = {Gul, H and Ramzan, M and Chung, JD and Chu, YM and Kadry, S}, title = {Multiple slips impact in the MHD hybrid nanofluid flow with Cattaneo-Christov heat flux and autocatalytic chemical reaction.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {14625}, pmid = {34272432}, issn = {2045-2322}, support = {20202020900060//Korea Institute of Energy Technology Evaluation and Planning/ ; }, abstract = {The present study deliberates the nanofluid flow containing multi and single-walled carbon nanotubes submerged into Ethylene glycol in a Darcy-Forchheimer permeable media over a stretching cylinder with multiple slips. The innovation of the envisaged mathematical model is enriched by considering the impacts of non-uniform source/sink and modified Fourier law in the energy equation and autocatalytic chemical reaction in the concentration equation. Entropy optimization analysis of the mathematical model is also performed in the present problem. Pertinent transformations procedure is implemented for the conversion of the non-linear system to the ordinary differential equations. The succor of the Shooting technique combined with the bvp4c MATLAB software is utilized for the solution of a highly nonlinear system of equations. The impacts of the leading parameters versus engaged fields are inspected through graphical sketches. The outcomes show that a strong magnetic field strengthens the temperature profile and decays the velocity profile. Also, the fluid velocity is lessened for growing estimates of the parameter of slip. Additionally, it is detected that entropy number augmented for higher thermal relaxation parameter and Reynolds number. To substantiate the existing mathematical model, a comparison table is also added. An excellent correlation is achieved here.}, } @article {pmid34272408, year = {2021}, author = {Wang, H and Enders, A and Preuss, JA and Bahnemann, J and Heisterkamp, A and Torres-Mapa, ML}, title = {3D printed microfluidic lab-on-a-chip device for fiber-based dual beam optical manipulation.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {14584}, pmid = {34272408}, issn = {2045-2322}, abstract = {3D printing of microfluidic lab-on-a-chip devices enables rapid prototyping of robust and complex structures. In this work, we designed and fabricated a 3D printed lab-on-a-chip device for fiber-based dual beam optical manipulation. The final 3D printed chip offers three key features, such as (1) an optimized fiber channel design for precise alignment of optical fibers, (2) an optically clear window to visualize the trapping region, and (3) a sample channel which facilitates hydrodynamic focusing of samples. A square zig-zag structure incorporated in the sample channel increases the number of particles at the trapping site and focuses the cells and particles during experiments when operating the chip at low Reynolds number. To evaluate the performance of the device for optical manipulation, we implemented on-chip, fiber-based optical trapping of different-sized microscopic particles and performed trap stiffness measurements. In addition, optical stretching of MCF-7 cells was successfully accomplished for the purpose of studying the effects of a cytochalasin metabolite, pyrichalasin H, on cell elasticity. We observed distinct changes in the deformability of single cells treated with pyrichalasin H compared to untreated cells. These results demonstrate that 3D printed microfluidic lab-on-a-chip devices offer a cost-effective and customizable platform for applications in optical manipulation.}, } @article {pmid34271062, year = {2021}, author = {Dubey, A and B, V and Bég, OA and Gorla, RSR}, title = {Finite element computation of magneto-hemodynamic flow and heat transfer in a bifurcated artery with saccular aneurysm using the Carreau-Yasuda biorheological model.}, journal = {Microvascular research}, volume = {138}, number = {}, pages = {104221}, doi = {10.1016/j.mvr.2021.104221}, pmid = {34271062}, issn = {1095-9319}, mesh = {Aorta/*physiopathology ; Aortic Aneurysm/*physiopathology ; Blood Flow Velocity ; Computer Simulation ; Electric Conductivity ; Energy Transfer ; Finite Element Analysis ; *Hemorheology ; Hot Temperature ; Humans ; *Magnetic Fields ; *Models, Cardiovascular ; Pulsatile Flow ; Regional Blood Flow ; Stress, Mechanical ; Time Factors ; }, abstract = {"Existing computational fluid dynamics studies of blood flows have demonstrated that the lower wall stress and higher oscillatory shear index might be the cause of acceleration in atherogenesis of vascular walls in hemodynamics. To prevent the chances of aneurysm wall rupture in the saccular aneurysm at distal aortic bifurcation, clinical biomagnetic studies have shown that extra-corporeal magnetic fields can be deployed to regulate the blood flow. Motivated by these developments, in the current study a finite element computational fluid dynamics simulation has been conducted of unsteady two-dimensional non-Newtonian magneto-hemodynamic heat transfer in electrically conducting blood flow in a bifurcated artery featuring a saccular aneurysm. The fluid flow is assumed to be pulsatile, non-Newtonian and incompressible. The Carreau-Yasuda model is adopted for blood to mimic non-Newtonian characteristics. The transformed equations with appropriate boundary conditions are solved numerically by employing the finite element method with the variational approach in the FreeFEM++ code. Hydrodynamic and thermal characteristics are elucidated in detail for the effects of key non-dimensional parameters i.e. Reynolds number (Re = 14, 21, 100, 200), Prandtl number (Pr = 14, 21) and magnetic body force parameter (Hartmann number) (M = 0.6, 1.2, 1.5) at the aneurysm and throughout the arterial domain. The influence of vessel geometry on blood flow characteristics i.e. velocity, pressure and temperature fields are also visualized through instantaneous contour patterns. It is found that an increase in the magnetic parameter reduces the pressure but increases the skin-friction coefficient in the domain. The temperature decreases at the parent artery (inlet) and both the distant and prior artery with the increment in the Prandtl number. A higher Reynolds number also causes a reduction in velocity as well as in pressure. The blood flow shows different characteristic contours with time variation at the aneurysm as well as in the arterial segment. The novelty of the current research is therefore to present a combined approach amalgamating the Carreau-Yasuda model, heat transfer and magnetohydrodynamics with complex geometric features in realistic arterial hemodynamics with extensive visualization and interpretation, in order to generalize and extend previous studies. In previous studies these features have been considered separately and not simultaneously as in the current study. The present simulations reveal some novel features of biomagnetic hemodynamics in bifurcated arterial transport featuring a saccular aneurysm which are envisaged to be of relevance in furnishing improved characterization of the rheological biomagnetic hemodynamics of realistic aneurysmic bifurcations in clinical assessment, diagnosis and magnetic-assisted treatment of cardiovascular disease."}, } @article {pmid34266946, year = {2021}, author = {Han, E and Zhu, L and Shaevitz, JW and Stone, HA}, title = {Low-Reynolds-number, biflagellated Quincke swimmers with multiple forms of motion.}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {118}, number = {29}, pages = {}, pmid = {34266946}, issn = {1091-6490}, mesh = {Hydrodynamics ; Locomotion/*physiology ; *Models, Biological ; Motion ; Rheology ; Rotation ; }, abstract = {In the limit of zero Reynolds number (Re), swimmers propel themselves exploiting a series of nonreciprocal body motions. For an artificial swimmer, a proper selection of the power source is required to drive its motion, in cooperation with its geometric and mechanical properties. Although various external fields (magnetic, acoustic, optical, etc.) have been introduced, electric fields are rarely utilized to actuate such swimmers experimentally in unbounded space. Here we use uniform and static electric fields to demonstrate locomotion of a biflagellated sphere at low Re via Quincke rotation. These Quincke swimmers exhibit three different forms of motion, including a self-oscillatory state due to elastohydrodynamic-electrohydrodynamic interactions. Each form of motion follows a distinct trajectory in space. Our experiments and numerical results demonstrate a method to generate, and potentially control, the locomotion of artificial flagellated swimmers.}, } @article {pmid34260387, year = {2021}, author = {Zhang, B and Leishangthem, P and Ding, Y and Xu, X}, title = {An effective and efficient model of the near-field hydrodynamic interactions for active suspensions of bacteria.}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {118}, number = {28}, pages = {}, pmid = {34260387}, issn = {1091-6490}, mesh = {Computer Simulation ; Escherichia coli/*physiology ; *Hydrodynamics ; *Models, Biological ; Suspensions ; }, abstract = {Near-field hydrodynamic interactions in active fluids are essential to determine many important emergent behaviors observed, but have not been successfully modeled so far. In this work, we propose an effective model capturing the essence of the near-field hydrodynamic interactions through a tensorial coefficient of resistance, validated numerically by a pedagogic model system consisting of an Escherichia coli bacterium and a passive sphere. In a critical test case that studies the scattering angle of the bacterium-sphere pair dynamics, we prove that the near-field hydrodynamics can make a qualitative difference even for this simple two-body system: Calculations based on the proposed model reveal a region in parameter space where the bacterium is trapped by the passive sphere, a phenomenon that is regularly observed in experiments but cannot be explained by any existing model. In the end, we demonstrate that our model also leads to efficient simulation of active fluids with tens of thousands of bacteria, sufficiently large for investigations of many emergent behaviors.}, } @article {pmid34251258, year = {2021}, author = {Charakopoulos, A and Karakasidis, T and Sarris, I}, title = {Analysis of magnetohydrodynamic channel flow through complex network analysis.}, journal = {Chaos (Woodbury, N.Y.)}, volume = {31}, number = {4}, pages = {043123}, doi = {10.1063/5.0043817}, pmid = {34251258}, issn = {1089-7682}, abstract = {Velocity time series of hydrodynamic and magnetohydrodynamic (MHD) turbulent flow are analyzed by means of complex network analysis in order to understand the mechanism of fluid patterns modification due to the external magnetic field. Direct numerical simulations of two cases are used, one for the plane hydrodynamic turbulent channel flow at the low Reynolds number of 180, based on the friction velocity, and the corresponding MHD flow with an external streamwise magnetic field with a magnetic interaction number of 0.1. By applying the visibility graph algorithm, we first transformed the time series into networks and then we evaluated the network topological properties. Results show that the proposed network analysis is not only able to identify and detect dynamical transitions in the system's behavior that identifies three distinct fluid areas in accordance with turbulent flow theory but also can quantify the effect of the magnetic field on the time series transitions. Moreover, we find that the topological measures of networks without a magnetic field and as compared to the one with a magnetic field are statistically different within a 95% confidence interval. These results provide a way to discriminate and characterize the influence of the magnetic field on the turbulent flows.}, } @article {pmid34247118, year = {2021}, author = {Tang, TQ and Hsu, SY and Dahiya, A and Soh, CH and Lin, KC}, title = {Numerical modeling of pulsatile blood flow through a mini-oxygenator in artificial lungs.}, journal = {Computer methods and programs in biomedicine}, volume = {208}, number = {}, pages = {106241}, doi = {10.1016/j.cmpb.2021.106241}, pmid = {34247118}, issn = {1872-7565}, mesh = {Equipment Design ; Humans ; Hydrodynamics ; Lung ; *Oxygen ; *Oxygenators, Membrane ; Pulsatile Flow ; }, abstract = {While previous in vitro studies showed divergent results concerning the influence of pulsatile blood flow on oxygen advection in oxygenators, no study was done to investigate the uncertainty affected by blood flow dynamics. The aim of this study is to utilize a computational fluid dynamics model to clarify the debate concerning the influence of pulsatile blood flow on the oxygen transport. The computer model is based on a validated 2D finite volume approach that predicts oxygen transfer in pulsatile blood flow passing through a 300-micron hollow-fiber membrane bundle with a length of 254 mm, a building block for an artificial lung device. In this study, the flow parameters include the steady Reynolds number (Re = 2, 5, 10 and 20), Womersley parameter (Wo = 0.29, 0.38 and 0.53) and sinusoidal amplitude (A = 0.25, 0.5 and 0.75). Specifically, the computer model is extended to verify, for the first time, the previously measured O2 transport that was observed to be hindered by pulsating flow in the Biolung, developed by Michigan Critical Care Consultants. A comprehensive analysis is carried out on computed profiles and fields of oxygen partial pressure (PO2) and oxygen saturation (SO2) as a function of Re, Wo and A. Based on the present results, we observe the positive and negative effects of pulsatile flow on PO2 at different blood flow rates. Besides, the SO2 variation is not much influenced by the pulsatile flow conditions investigated. While being consistent with a recent experimental study, the computed O2 volume flow rate is found to be increased at high blood flow rates operated with low frequency and high amplitude. Furthermore, the present study qualitatively explains that divergent outcomes reported in previous in vitro experimental studies could be owing to the different blood flow rates adopted. Finally, the contour analysis reveals how the spatial distributions of PO2 and SO2 vary over time.}, } @article {pmid34243174, year = {2021}, author = {Meng, X and Ghaffar, A and Zhang, Y and Deng, C}, title = {Very low Reynolds number causes a monotonic force enhancement trend for a three-dimensional hovering wing in ground effect.}, journal = {Bioinspiration & biomimetics}, volume = {16}, number = {5}, pages = {}, doi = {10.1088/1748-3190/ac1308}, pmid = {34243174}, issn = {1748-3190}, mesh = {Animals ; Biomechanical Phenomena ; *Flight, Animal ; Insecta ; Models, Biological ; *Wings, Animal ; }, abstract = {This research reports the numerical results of the ground effect trend for a three-dimensional flapping insect wing at a very low Reynolds number (Re = 10). It demonstrates that the ground effect trend at this Re has a 'single force regime,' i.e. the forces only enhance as the ground distance decreases. This phenomenon is unlike the widely expected non-monotonic trend publicized in previous studies for higher Reynolds numbers, that shows 'three force regimes,' i.e. the forces reduce, recover, and also enhance as the ground distance decreases. The force trend in the ground effect correlates to a similar trend in wing-wake interaction or the downwash strength on the wing's head. At very low Re (10), the very large viscosity causes diffused vortices and less advected vortex wake, while at relatively high Re, the vortices are easily separated from the wing and then advected downwards. This different development of the vortex wake caused different force trends for the flapping wing in the ground effect. Furthermore, by examining only the first stroke when there is no vortex wake, we found that the 'ramming effect' enhances the forces on the wing. This effect increases the pressure of the lower wing surface due to the squeezed air between the wing and the ground. The 'ramming effect', combined with the reduced downwash (or wing-wake interaction) effect, causes the force enhancement of the wing near the ground's vicinity. It is further comprehended that the trend is dependent on Re. As the Re is increased, the trend becomes non-monotonic. The effect of varying angles of attack, flapping amplitude and wing planform at very low Re does not change this trend. This ground effect might help insects by enhancing their lift while they hover above the surface. This finding might prove beneficial for developing micro air vehicles.}, } @article {pmid34241532, year = {2021}, author = {Iyer, KP and Bewley, GP and Biferale, L and Sreenivasan, KR and Yeung, PK}, title = {Oscillations Modulating Power Law Exponents in Isotropic Turbulence: Comparison of Experiments with Simulations.}, journal = {Physical review letters}, volume = {126}, number = {25}, pages = {254501}, doi = {10.1103/PhysRevLett.126.254501}, pmid = {34241532}, issn = {1079-7114}, abstract = {Inertial-range features of turbulence are investigated using data from experimental measurements of grid turbulence and direct numerical simulations of isotropic turbulence simulated in a periodic box, both at the Taylor-scale Reynolds number R_{λ}∼1000. In particular, oscillations modulating the power-law scaling in the inertial range are examined for structure functions up to sixth-order moments. The oscillations in exponent ratios decrease with increasing sample size in simulations, although in experiments they survive at a low value of 4 parts in 1000 even after massive averaging. The two datasets are consistent in their intermittent character but differ in small but observable respects. Neither the scaling exponents themselves nor all the viscous effects are consistently reproduced by existing models of intermittency.}, } @article {pmid34241478, year = {2021}, author = {Gojon, R and Jardin, T and Parisot-Dupuis, H}, title = {Experimental investigation of low Reynolds number rotor noise.}, journal = {The Journal of the Acoustical Society of America}, volume = {149}, number = {6}, pages = {3813}, doi = {10.1121/10.0005068}, pmid = {34241478}, issn = {1520-8524}, abstract = {In this paper, an experimental characterisation of low Reynolds number rotors is performed in an anechoic room. Two commercially available two-bladed rotors as well as four three-dimensional (3D)-printed rotors with different numbers of blades (from two to five) are tested. The latter have canonical geometry, with an NACA0012 blade section profile, extruded in the radial direction with constant chord and constant 10° pitch. The experimental setup and the 3D printing strategy are first validated using results from the literature for the commercially available rotors. For all the tested rotors, four noise characteristics are analysed: the overall sound pressure level (OASPL), the amplitude of the blade passing frequency (BPF), and the amplitude of its first harmonic and the high-frequency broadband noise. For all the rotors, an increase in all noise characteristics is observed with the rotational speed (rpm) for all directivity angles. Moreover, an interesting change of pattern is observed for the amplitudes of the BPF and of its first harmonic, with, in the vicinity of the rotor plane, a minimum value for low rpm and/or high number of blades, and a maximum value for high rpm and/or low number of blades. This change in directivity leads to a similar change of directivity of the OASPL. For the broadband noise, a dipole-like pattern is obtained with a minimum value at θ=-10°, i.e., aligned with the trailing edge and thus indicating the generation of trailing edge noise. Finally, scaling laws that characterise the amplitude of the different noise components with respect to the rpm are proposed.}, } @article {pmid34234957, year = {2021}, author = {Mazharmanesh, S and Stallard, J and Medina, A and Fisher, A and Ando, N and Tian, FB and Young, J and Ravi, S}, title = {Effects of uniform vertical inflow perturbations on the performance of flapping wings.}, journal = {Royal Society open science}, volume = {8}, number = {6}, pages = {210471}, pmid = {34234957}, issn = {2054-5703}, abstract = {Flapping wings have attracted significant interest for use in miniature unmanned flying vehicles. Although numerous studies have investigated the performance of flapping wings under quiescent conditions, effects of freestream disturbances on their performance remain under-explored. In this study, we experimentally investigated the effects of uniform vertical inflows on flapping wings using a Reynolds-scaled apparatus operating in water at Reynolds number ≈ 3600. The overall lift and drag produced by a flapping wing were measured by varying the magnitude of inflow perturbation from J Vert = -1 (downward inflow) to J Vert = 1 (upward inflow), where J Vert is the ratio of the inflow velocity to the wing's velocity. The interaction between flapping wing and downward-oriented inflows resulted in a steady linear reduction in mean lift and drag coefficients, C ¯ L and C ¯ D , with increasing inflow magnitude. While a steady linear increase in C ¯ L and C ¯ D was noted for upward-oriented inflows between 0 < J Vert < 0.3 and J Vert > 0.7, a significant unsteady wing-wake interaction occurred when 0.3 ≤ J Vert < 0.7, which caused large variations in instantaneous forces over the wing and led to a reduction in mean performance. These findings highlight asymmetrical effects of vertically oriented perturbations on the performance of flapping wings and pave the way for development of suitable control strategies.}, } @article {pmid34234155, year = {2021}, author = {Connolly, S and Newport, D and McGourty, K}, title = {Cell specific variation in viability in suspension in in vitro Poiseuille flow conditions.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {13997}, pmid = {34234155}, issn = {2045-2322}, mesh = {Algorithms ; Cell Line, Tumor ; *Cell Survival ; Fibroblasts ; Humans ; *Lab-On-A-Chip Devices ; *Microfluidic Analytical Techniques ; *Models, Theoretical ; Neoplastic Cells, Circulating ; Suspensions ; T-Lymphocytes ; }, abstract = {The influence of Poiseuille flow on cell viability has applications in the areas of cancer metastasis, lab-on-a-chip devices and flow cytometry. Indeed, retaining cell viability is important in the emerging field of adoptive cell therapy, as cells need to be returned to patients' bodies, while the viability of other cells, which are perhaps less accustomed to suspension in a fluidic environment, is important to retain in flow cytometers and other such devices. Despite this, it is unclear how Poiseuille flow affects cell viability. Following on from previous studies which investigated the viability and inertial positions of circulating breast cancer cells in identical flow conditions, this study investigated the influence that varying flow rate, and the corresponding Reynolds number has on the viability of a range of different circulating cells in laminar pipe flow including primary T-cells, primary fibroblasts and neuroblastoma cells. It was found that Reynolds numbers as high as 9.13 had no effect on T-cells while the viabilities of neuroblastoma cells and intestinal fibroblasts were significantly reduced in comparison. This indicates that in vitro flow devices need to be tailored to cell-specific flow regimes.}, } @article {pmid34208685, year = {2021}, author = {Shanbrom, C and Balisacan, J and Wilkens, G and Chyba, M}, title = {Geometric Methods for Efficient Planar Swimming of Copepod Nauplii.}, journal = {Micromachines}, volume = {12}, number = {6}, pages = {}, pmid = {34208685}, issn = {2072-666X}, support = {359510//Simons Foundation/ ; }, abstract = {Copepod nauplii are larval crustaceans with important ecological functions. Due to their small size, they experience an environment of low Reynolds number within their aquatic habitat. Here we provide a mathematical model of a swimming copepod nauplius with two legs moving in a plane. This model allows for both rotation and two-dimensional displacement by the periodic deformation of the swimmer's body. The system is studied from the framework of optimal control theory, with a simple cost function designed to approximate the mechanical energy expended by the copepod. We find that this model is sufficiently realistic to recreate behavior similar to those of observed copepod nauplii, yet much of the mathematical analysis is tractable. In particular, we show that the system is controllable, but there exist singular configurations where the degree of non-holonomy is non-generic. We also partially characterize the abnormal extremals and provide explicit examples of families of abnormal curves. Finally, we numerically simulate normal extremals and observe some interesting and surprising phenomena.}, } @article {pmid34204328, year = {2021}, author = {Ali, A and Bukhari, Z and Umar, M and Ismail, MA and Abbas, Z}, title = {Cu and Cu-SWCNT Nanoparticles' Suspension in Pulsatile Casson Fluid Flow via Darcy-Forchheimer Porous Channel with Compliant Walls: A Prospective Model for Blood Flow in Stenosed Arteries.}, journal = {International journal of molecular sciences}, volume = {22}, number = {12}, pages = {}, pmid = {34204328}, issn = {1422-0067}, mesh = {Algorithms ; Arteries/pathology/physiopathology ; Blood Circulation ; Constriction, Pathologic ; *Copper/chemistry ; *Hemodynamics ; Humans ; *Hydrodynamics ; *Metal Nanoparticles/chemistry ; *Models, Cardiovascular ; Porosity ; *Pulsatile Flow ; Suspensions ; }, abstract = {The use of experimental relations to approximate the efficient thermophysical properties of a nanofluid (NF) with Cu nanoparticles (NPs) and hybrid nanofluid (HNF) with Cu-SWCNT NPs and subsequently model the two-dimensional pulsatile Casson fluid flow under the impact of the magnetic field and thermal radiation is a novelty of the current study. Heat and mass transfer analysis of the pulsatile flow of non-Newtonian Casson HNF via a Darcy-Forchheimer porous channel with compliant walls is presented. Such a problem offers a prospective model to study the blood flow via stenosed arteries. A finite-difference flow solver is used to numerically solve the system obtained using the vorticity stream function formulation on the time-dependent governing equations. The behavior of Cu-based NF and Cu-SWCNT-based HNF on the wall shear stress (WSS), velocity, temperature, and concentration profiles are analyzed graphically. The influence of the Casson parameter, radiation parameter, Hartmann number, Darcy number, Soret number, Reynolds number, Strouhal number, and Peclet number on the flow profiles are analyzed. Furthermore, the influence of the flow parameters on the non-dimensional numbers such as the skin friction coefficient, Nusselt number, and Sherwood number is also discussed. These quantities escalate as the Reynolds number is enhanced and reduce by escalating the porosity parameter. The Peclet number shows a high impact on the microorganism's density in a blood NF. The HNF has been shown to have superior thermal properties to the traditional one. These results could help in devising hydraulic treatments for blood flow in highly stenosed arteries, biomechanical system design, and industrial plants in which flow pulsation is essential.}, } @article {pmid34203635, year = {2021}, author = {Ju, Y and Zhu, T and Mashayekhi, R and Mohammed, HI and Khan, A and Talebizadehsardari, P and Yaïci, W}, title = {Evaluation of Multiple Semi-Twisted Tape Inserts in a Heat Exchanger Pipe Using Al2O3 Nanofluid.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {11}, number = {6}, pages = {}, pmid = {34203635}, issn = {2079-4991}, abstract = {The hydrothermal performance of multiple semi-twisted tape inserts inside a heat exchanger pipe is numerically examined in three-dimensions. This study aims to find the optimum case for having the highest heat transfer enhancement with the lowest friction factor using nanofluid (Al2O3/water). A performance evaluation criterion (PEC) is defined to characterize the performance based on both friction factor and heat transfer. It was found that increasing the number of semi-twisted tapes increases the number of swirl flow streams and leads to an enhancement in the local Nusselt number as well as the friction factor. The average Nusselt number increases from 15.13 to 28.42 and the average friction factor enhances from 0.022 to 0.052 by increasing the number of the semi-twisted tapes from 0 to 4 for the Reynolds number of 1000 for the base fluid. By using four semi-twisted tapes, the average Nusselt number increases from 12.5 to 28.5, while the friction factor reduces from 0.155 to 0.052 when the Reynolds number increases from 250 to 1000 for the base fluid. For the Reynolds number of 1000, the increase in nanofluid concentration from 0 to 3% improves the average Nusselt number and friction factor by 6.41% and 2.29%, respectively. The highest PEC is equal to 1.66 and belongs to the Reynolds number of 750 using four semi-twisted tape inserts with 3% nanoparticles. This work offers instructions to model an advanced design of twisted tape integrated with tubes using multiple semi-twisted tapes, which helps to provide a higher amount of energy demand for solar applications.}, } @article {pmid34199619, year = {2021}, author = {Elsafy, KM and Saghir, MZ}, title = {Forced Convection in Wavy Microchannels Porous Media Using TiO2 and Al2O3-Cu Nanoparticles in Water Base Fluids: Numerical Results.}, journal = {Micromachines}, volume = {12}, number = {6}, pages = {}, pmid = {34199619}, issn = {2072-666X}, abstract = {In the present work, an attempt is made to investigate the performance of three fluids with forced convection in a wavy channel. The fluids are water, a nanofluid of 1% TiO2 in a water solution and a hybrid fluid which consists of 1% Al2O3-Cu nanoparticles in a water solution. The wavy channel has a porous insert with a permeability of 10 PPI, 20 PPI and 40 PPI, respectively. Since Reynolds number is less than 1000, the flow is assumed laminar, Newtonian and steady state. Results revealed that wavy channel provides a better heat enhancement than a straight channel of the same dimension. Porous material increases heat extraction at the expenses of the pressure drop. The nanofluid of 1% TiO2 in water provided the highest performance evaluation criteria.}, } @article {pmid34185996, year = {2021}, author = {Ahmed, S and Perez-Mercader, J}, title = {Autonomous Low-Reynolds-Number Soft Robots with Structurally Encoded Motion and Their Thermodynamic Efficiency.}, journal = {Langmuir : the ACS journal of surfaces and colloids}, volume = {37}, number = {27}, pages = {8148-8156}, doi = {10.1021/acs.langmuir.1c00765}, pmid = {34185996}, issn = {1520-5827}, support = {1541959//National Science Foundation/ ; }, mesh = {Biocompatible Materials ; Motion ; *Robotics ; Thermodynamics ; }, abstract = {Soft low-Reynolds-number robotics hold the potential to significantly impact numerous fields including drug delivery, sensing, and diagnostics. Realizing this potential is predicated upon the ability to design soft robots tailored to their intended function. In this work, we identify the effect of different geometric and symmetry parameters on the motion of soft, autonomous robots that operate in the low-Reynolds-number regime and use organic fuel. The ability to power low-Reynolds-number soft robots using an organic fuel would provide a new avenue for their potential use in biomedical applications, as is the use of a polymeric biocompatible material as is done here. We introduce a simple and cost-effective 3D-printer-assisted method to fabricate robots of different shapes that is scalable and widely applicable for a variety of materials. The efficiency of chemical energy to mechanical energy conversion is measured in soft low-Reynolds-number robots for the first time, and their mechanism of motion is assessed. Motion is a result of a periodic and oscillatory change in the charge state of the gel. This work lays the groundwork for the structure-function design of soft, chemically operated, and autonomous low-Reynolds-number robots.}, } @article {pmid34184223, year = {2021}, author = {Yang, F and Zeng, YH and Huai, WX}, title = {A new model for settling velocity of non-spherical particles.}, journal = {Environmental science and pollution research international}, volume = {28}, number = {43}, pages = {61636-61646}, pmid = {34184223}, issn = {1614-7499}, support = {51879197//National Natural Science Foundation of China/ ; 51622905//National Natural Science Foundation of China/ ; 2016YFA0600901//National key research and development of China/ ; }, mesh = {*Ecosystem ; Particle Size ; }, abstract = {The settlement of non-spherical particles, such as propagules of plants and natural sediments, is commonly observed in riverine ecosystems. The settling process is influenced by both particle properties (size, density, and shape) and fluid properties (density and viscosity). Therefore, the drag law of non-spherical particles is a function of both particle Reynolds number and particle shape. Herein, a total of 828 settling data are collected from the literatures, which cover a wide range of particle Reynolds number (0.008-10000). To characterize the influence of particle shapes, sphericity is adopted as the general shape factor, which varies from 0.421 to 1.0. By comparing the measured drag with the standard drag curve of spheres, we modify the spherical drag law with three shape-dependent functions to develop a new drag law for non-spherical particles. Combined with an iterative procedure, a new model is thus obtained to predict the settling velocity of non-spherical particles of various shapes and materials. Further applications in hydrochorous propagule dispersal and sediment transport are projected based on deeper understanding of the settling process.}, } @article {pmid34143104, year = {2021}, author = {Hill, JL and Hsu, PS and Jiang, N and Grib, SW and Roy, S and Borg, M and Thomas, L and Reeder, M and Schumaker, SA}, title = {Hypersonic N2 boundary layer flow velocity profile measurements using FLEET.}, journal = {Applied optics}, volume = {60}, number = {15}, pages = {C38-C46}, doi = {10.1364/AO.417470}, pmid = {34143104}, issn = {1539-4522}, abstract = {Femtosecond laser electronic excitation tagging (FLEET) velocimetry was used in the boundary layer of an ogive-cylinder model in a Mach-6 Ludwieg tube. One-dimensional velocity profiles were extracted from the FLEET signal in laminar boundary layers from pure N2 flows at unit Reynolds numbers ranging from 3.4×10[6]/m to3.9×10[6]/m. The effects of model tip bluntness and the unit Reynolds number on the velocity profiles were investigated. The challenges and strategies of applying FLEET for direct boundary layer velocity measurement are discussed. The potential of utilizing FLEET velocimetry for understanding the dynamics of laminar and turbulent boundary layers in hypersonic flows is demonstrated.}, } @article {pmid34139680, year = {2021}, author = {Mazharmanesh, S and Stallard, J and Medina, A and Fisher, A and Ando, N and Tian, FB and Young, J and Ravi, S}, title = {Performance of passively pitching flapping wings in the presence of vertical inflows.}, journal = {Bioinspiration & biomimetics}, volume = {16}, number = {5}, pages = {}, doi = {10.1088/1748-3190/ac0c60}, pmid = {34139680}, issn = {1748-3190}, mesh = {Animals ; Biomechanical Phenomena ; *Flight, Animal ; *Models, Biological ; Wings, Animal ; }, abstract = {The successful implementation of passively pitching flapping wings strongly depends on their ability to operate efficiently in wind disturbances. In this study, we experimentally investigated the interaction between a uniform vertical inflow perturbation and a passive-pitching flapping wing using a Reynolds-scaled apparatus operating in water at Reynolds number ≈3600. A parametric study was performed by systematically varying the Cauchy number (Ch) of the wings from 0.09 to 11.52. The overall lift and drag, and pitch angle of the wing were measured by varying the magnitude of perturbation fromJVert= -0.6 (downward inflow) toJVert= 0.6 (upward inflow) at eachCh, whereJVertis the ratio of the inflow velocity to the wing's velocity. We found that the lift and drag had remarkably different characteristics in response to bothChandJVert. Across allCh, while mean lift tended to increase as the inflow perturbation varied from -0.6 to 0.6, drag was significantly less sensitive to the perturbation. However effect of the vertical inflow on drag was dependent onCh, where it tended to vary from an increasing to a decreasing trend asChwas changed from 0.09 to 11.52. The differences in the lift and drag with perturbation magnitude could be attributed to the reorientation of the net force over the wing as a result of the interaction with the perturbation. These results highlight the complex interactions between passively pitching flapping wings and freestream perturbations and will guide the design of miniature flying crafts with such architectures.}, } @article {pmid34134196, year = {2021}, author = {Li, H and Tian, B and He, Z and Zhang, Y}, title = {Growth mechanism of interfacial fluid-mixing width induced by successive nonlinear wave interactions.}, journal = {Physical review. E}, volume = {103}, number = {5-1}, pages = {053109}, doi = {10.1103/PhysRevE.103.053109}, pmid = {34134196}, issn = {2470-0053}, abstract = {Interfacial fluid mixing induced by successive waves, such as shock, rarefaction, and compression waves, plays a fundamental role in engineering applications, e.g., inertial confinement fusion, and in natural phenomena, e.g., supernova explosion. These waves bring nonuniform, unsteady external forces into the mixing zone, which leads to a complex mixing process. The growth rate of the mixing width is analyzed by decomposing the turbulent flow field into the averaged field and the fluctuating counterpart. The growth rate is thus divided into three parts: (i) the stretching or compression (S(C)) effect induced by the averaged-velocity difference between two ends of the mixing zone, (ii) the penetration effect induced by the fluctuations which represent the penetration of the two species into each other, and (iii) the diffusive effect, which is induced by the molecular diffusion and is negligible in high-Reynolds-number flows at Schmidt number of order unity. The penetration effect is further divided into the Richtmyer-Meshkov (RM) effect, which is induced by fluctuations that were deposited by earlier wave interactions, and the Rayleigh-Taylor (RT) effect, which is caused by the fluctuations that arise in an overall acceleration of the mixing zone. During the passage of the rarefaction waves, the mixing zone is stretched, while during the passage of the compression waves or shock waves, the mixing zone is compressed. To illustrate these effects, a physical model of RM mixing with reshock is used. By combining the S(C), RM, and RT effects, the entire evolution of mixing width is restructured, which agrees well with numerical simulations for problems with a wide range of density ratios.}, } @article {pmid34129919, year = {2021}, author = {Ahookhosh, K and Saidi, M and Mohammadpourfard, M and Aminfar, H and Hamishehkar, H and Farnoud, A and Schmid, O}, title = {Flow Structure and Particle Deposition Analyses for Optimization of a Pressurized Metered Dose Inhaler (pMDI) in a Model of Tracheobronchial Airway.}, journal = {European journal of pharmaceutical sciences : official journal of the European Federation for Pharmaceutical Sciences}, volume = {164}, number = {}, pages = {105911}, doi = {10.1016/j.ejps.2021.105911}, pmid = {34129919}, issn = {1879-0720}, mesh = {Administration, Inhalation ; Adult ; Aerosols ; Equipment Design ; Female ; Humans ; Lung ; *Metered Dose Inhalers ; *Nebulizers and Vaporizers ; Particle Size ; }, abstract = {Inhalation therapy plays an important role in management or treatment of respiratory diseases such asthma and chronic obstructive pulmonary diseases (COPDs). For decades, pressurized metered dose inhalers (pMDIs) have been the most popular and prescribed drug delivery devices for inhalation therapy. The main objectives of the present computational work are to study flow structure inside a pMDI, as well as transport and deposition of micron-sized particles in a model of human tracheobronchial airways and their dependence on inhalation air flow rate and characteristic pMDI parameters. The upper airway geometry, which includes the extrathoracic region, trachea, and bronchial airways up to the fourth generation in some branches, was constructed based on computed tomography (CT) images of an adult healthy female. Computational fluid dynamics (CFD) simulation was employed using the k-ω model with low-Reynolds number (LRN) corrections to accomplish the objectives. The deposition results of the present study were verified with the in vitro deposition data of our previous investigation on pulmonary drug delivery using a hollow replica of the same airway geometry as used for CFD modeling. It was found that the flow structure inside the pMDI and extrathoracic region strongly depends on inhalation flow rate and geometry of the inhaler. In addition, regional aerosol deposition patterns were investigated at four inhalation flow rates between 30 and 120 L/min and for 60 L/min yielding highest deposition fractions of 24.4% and 3.1% for the extrathoracic region (EX) and the trachea, respectively. It was also revealed that particle deposition was larger in the right branches of the bronchial airways (right lung) than the left branches (left lung) for all of the considered cases. Also, optimization of spray characteristics showed that the optimum values for initial spray velocity, spray cone angle and spray duration were 100 m/s, 10° and 0.1 sec, respectively. Moreover, spray cone angle, more than any other of the investigated pMDI parameters can change the deposition pattern of inhaled particles in the airway model. In conclusion, the present investigation provides a validated CFD model for particle deposition and new insights into the relevance of flow structure for deposition of pMDI-emitted pharmaceutical aerosols in the upper respiratory tract.}, } @article {pmid34127716, year = {2021}, author = {Shah, Z and Jafaryar, M and Sheikholeslami, M and Ikramullah, and Kumam, P}, title = {Heat transfer intensification of nanomaterial with involve of swirl flow device concerning entropy generation.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {12504}, pmid = {34127716}, issn = {2045-2322}, abstract = {The thermal features of hybrid nano-powder turbulent motion through a pipe employing helical turbulator is numerically simulated via Finite Volume Method (FVM). The hybrid nanofluid (MWCNTs + Fe3O4 + H2O) is obtained by uniformly dispersing MWCNTs + Fe3O4 nanomaterials in H2O. The characteristics features of thermal energy transfer of hybrid nanofluid are investigated by varying the pitch ratio (P) of the helical turbulator and Reynolds number (Re) of the fluid. The outputs of the study are depicted in terms of contour plots of temperature, velocity, frictional irreversibility Sgen,f, and thermal irreversibility Sgen,th. The variation of Sgen,f, and Sgen,th with changing P and Re are also displayed by 3D plots. It is found that making the fluid more turbulent by increasing Re, the temperature of the fluid drops whereas the fluid velocity augments. The frictional irreversibility enhances, whereas the thermal irreversibility drops with the increasing turbulent motion. The decreasing P causes to drop the temperature of the higher turbulent fluid flow, while opposite effect is observed for smaller Re. The decreasing P causes to enhance the fluid mixing and thus augments the fluid velocity. Sgen,f and Sgen,th both augment with decreasing P. The comparison of current outputs with the older article shows an acceptable accuracy. The results of the present investigation will be useful in modelling of efficient thermal energy transfer systems.}, } @article {pmid34124445, year = {2021}, author = {Tian, G and Zhu, Y and Feng, X and Zhou, H and Zhang, Y}, title = {Investigation of the Turbulent Boundary Layer Structure over a Sparsely Spaced Biomimetic Spine-Covered Protrusion Surface.}, journal = {ACS omega}, volume = {6}, number = {22}, pages = {14220-14229}, pmid = {34124445}, issn = {2470-1343}, abstract = {Multiperspective particle image velocimetry was used to investigate the turbulent boundary layer structure over biomimetic spine-covered protrusion (BSCP) samples inspired by dorsal skin of pufferfish. The comparison of BSCP samples of two sparse "k-type" arrangements (aligned and staggered) with roughness height k [+] = 5-7 (nearly hydraulically smooth) and smooth case were manufactured in bulk Reynolds number Re b = 37,091, 44,510. The negative value of the roughness function ΔU [+] shows a downward shift of the mean velocity profile of BSCP samples, which shows a drag reduction effect. The results of turbulent statistics present strong fluctuation over the aligned case in the streamwise direction, while little influence is observed in the wall-normal and spanwise direction, which promotes turbulence stability. The same phenomenon was found based on the probability density function of fluctuation velocity that the suppression of turbulent flow is better over the staggered case. It is obvious that the shear stress induced is governed by the streamwise fluctuations. Furthermore, the Q-criterion and the λci-criterion improved with vorticity ω were introduced for vortex identification, which indicates less prograde vortex population and weaker swirling strength over BSCP samples than over the smooth one. Finally, the spatial coherent structure appeared similar and more orderly over the staggered case in the streamwise and wall-normal direction based on the analysis of two-point correlations R uu. These results provide further guidance to reveal the mechanism of drag reduction on the BSCP surface.}, } @article {pmid34111118, year = {2021}, author = {Velho Rodrigues, MF and Lisicki, M and Lauga, E}, title = {The bank of swimming organisms at the micron scale (BOSO-Micro).}, journal = {PloS one}, volume = {16}, number = {6}, pages = {e0252291}, pmid = {34111118}, issn = {1932-6203}, mesh = {Biodiversity ; Biomechanical Phenomena ; Flagella ; Locomotion ; *Microbiology ; Swimming ; }, abstract = {Unicellular microscopic organisms living in aqueous environments outnumber all other creatures on Earth. A large proportion of them are able to self-propel in fluids with a vast diversity of swimming gaits and motility patterns. In this paper we present a biophysical survey of the available experimental data produced to date on the characteristics of motile behaviour in unicellular microswimmers. We assemble from the available literature empirical data on the motility of four broad categories of organisms: bacteria (and archaea), flagellated eukaryotes, spermatozoa and ciliates. Whenever possible, we gather the following biological, morphological, kinematic and dynamical parameters: species, geometry and size of the organisms, swimming speeds, actuation frequencies, actuation amplitudes, number of flagella and properties of the surrounding fluid. We then organise the data using the established fluid mechanics principles for propulsion at low Reynolds number. Specifically, we use theoretical biophysical models for the locomotion of cells within the same taxonomic groups of organisms as a means of rationalising the raw material we have assembled, while demonstrating the variability for organisms of different species within the same group. The material gathered in our work is an attempt to summarise the available experimental data in the field, providing a convenient and practical reference point for future studies.}, } @article {pmid34091219, year = {2021}, author = {Amani, M and Amani, P and Bahiraei, M and Ghalambaz, M and Ahmadi, G and Wang, LP and Wongwises, S and Mahian, O}, title = {Latest developments in nanofluid flow and heat transfer between parallel surfaces: A critical review.}, journal = {Advances in colloid and interface science}, volume = {294}, number = {}, pages = {102450}, doi = {10.1016/j.cis.2021.102450}, pmid = {34091219}, issn = {1873-3727}, abstract = {The enhancement of heat transfer between parallel surfaces, including parallel plates, parallel disks, and two concentric pipes, is vital because of their wide applications ranging from lubrication systems to water purification processes. Various techniques can be utilized to enhance heat transfer in such systems. Adding nanoparticles to the conventional working fluids is an effective solution that could remarkably enhance the heat transfer rate. No published review article focuses on the recent advances in nanofluid flow between parallel surfaces; therefore, the present paper aims to review the latest experimental and numerical studies on the flow and heat transfer of nanofluids (mixtures of nanoparticles and conventional working fluids) in such configurations. For the performance analysis of thermal systems composed of parallel surfaces and operating with nanofluids, it is necessary to know the physical phenomena and parameters that influence the flow and heat transfer characteristics in these systems. Significant results obtained from this review indicate that, in most cases, the heat transfer rate between parallel surfaces is enhanced with an increase in the Rayleigh number, the Reynolds number, the magnetic number, and Brownian motion. On the other hand, an increase in thermophoresis parameter, as well as flow parameters, including the Eckert number, buoyancy ratio, Hartmann number, and Lewis number, leads to heat transfer rate reduction.}, } @article {pmid34081994, year = {2021}, author = {Das, S and Pal, TK and Jana, RN and Giri, B}, title = {Significance of Hall currents on hybrid nano-blood flow through an inclined artery having mild stenosis: Homotopy perturbation approach.}, journal = {Microvascular research}, volume = {137}, number = {}, pages = {104192}, doi = {10.1016/j.mvr.2021.104192}, pmid = {34081994}, issn = {1095-9319}, mesh = {Animals ; Arterial Occlusive Diseases/*physiopathology ; Arteries/*physiopathology ; Constriction, Pathologic ; Copper/*chemistry ; *Hemodynamics ; Humans ; *Metal Nanoparticles ; *Models, Cardiovascular ; *Nanotechnology ; Porosity ; Regional Blood Flow ; Stress, Mechanical ; }, abstract = {The rheological perspective of blood flow with the suspension of metallic or non-metallic nanoparticles through arteries having cardiovascular diseases is getting more attention due to momentous applications in obstructed hemodynamics, nano-hemodynamics, nano-pharmacology, blood purification system, treatment of hemodynamic ailments, etc. Motivated by the novel significance and research in this direction, a mathematical hemodynamics model is developed to mimic the hemodynamic features of blood flow under the concentration of hybrid nanoparticles through an inclined artery with mild stenosis in the existence of dominating electromagnetic field force, Hall currents, heat source, and porous substance. Copper (Cu) and copper oxide (CuO) nanoparticles are submerged into the blood to form hybrid nano-blood suspension (Cu-CuO/blood). The attribute of the medium porosity on the blood flow is featured by Darcy's law. The mathematical equations describing the flow are formulated and simplified under mild stenosis and small Reynolds number assumptions. To determine the analytical solution of the resulting nonlinear momentum equation, the homotopy perturbation method (HPM) is employed. Several figures are graphed to assess the hemodynamical contributions of various intricate physical parameters on blood flow phenomena through the inclined stenosed artery. Significant outcomes from graphical elucidation envisage that the hemodynamic resistance to the blood flow is reduced due to the dispersion of more hybrid nanoparticles in the blood. The hemodynamic resistance (impedance) increases approximately two times by dispersing 0.11% hybrid nanoparticles in the blood flow. The temperature of Cu-CuO/blood is found to be lower in comparison to Cu-blood and pure blood. Intensification of Hall parameter attenuates the wall shear stress at the arterial wall. The trapping phenomena are also outlined via streamline plots which exemplify the blood flow pattern in the stenosed artery under the variation of the emerging parameters. As anticipated, the addition of a large number of hybrid nanoparticles significantly modulates the blood flow pattern in the stenotic region. The novel feature of this model is the impressive impact of Hall currents on hybrid nanoparticle doped blood flow through the stenosed artery. There is another piece of significance is that HPM is the most suitable method to handle the nonlinear momentum equation under the aforementioned flow constraints. Outcomes of this simulation may be valuable for advanced study and research in biomedical engineering, bio-nanofluid mechanics, nano-pharmacodynamics.}, } @article {pmid34078976, year = {2021}, author = {Usman, AH and Khan, NS and Humphries, UW and Ullah, Z and Shah, Q and Kumam, P and Thounthong, P and Khan, W and Kaewkhao, A and Bhaumik, A}, title = {Computational optimization for the deposition of bioconvection thin Oldroyd-B nanofluid with entropy generation.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {11641}, pmid = {34078976}, issn = {2045-2322}, abstract = {The behavior of an Oldroyd-B nanoliquid film sprayed on a stretching cylinder is investigated. The system also contains gyrotactic microorganisms with heat and mass transfer flow. Similarity transformations are used to make the governing equations non-dimensional ordinary differential equations and subsequently are solved through an efficient and powerful analytic technique namely homotopy analysis method (HAM). The roles of all dimensionless profiles and spray rate have been investigated. Velocity decreases with the magnetic field strength and Oldroyd-B nanofluid parameter. Temperature is increased with increasing the Brownian motion parameter while it is decreased with the increasing values of Prandtl and Reynolds numbers. Nanoparticle's concentration is enhanced with the higher values of Reynolds number and activation energy parameter. Gyrotactic microorganism density increases with bioconvection Rayleigh number while it decreases with Peclet number. The film size naturally increases with the spray rate in a nonlinear way. A close agreement is achieved by comparing the present results with the published results.}, } @article {pmid34076781, year = {2021}, author = {Kadiri, VM and Günther, JP and Kottapalli, SN and Goyal, R and Peter, F and Alarcón-Correa, M and Son, K and Barad, HN and Börsch, M and Fischer, P}, title = {Light- and magnetically actuated FePt microswimmers.}, journal = {The European physical journal. E, Soft matter}, volume = {44}, number = {6}, pages = {74}, pmid = {34076781}, issn = {1292-895X}, support = {253407113//Deutsche Forschungsgemeinschaft/ ; }, abstract = {Externally controlled microswimmers offer prospects for transport in biological research and medical applications. This requires biocompatibility of the swimmers and the possibility to tailor their propulsion mechanisms to the respective low Reynolds number environment. Here, we incorporate low amounts of the biocompatible alloy of iron and platinum (FePt) in its [Formula: see text] phase in microstructures by a versatile one-step physical vapor deposition process. We show that the hard magnetic properties of [Formula: see text] FePt are beneficial for the propulsion of helical micropropellers with rotating magnetic fields. Finally, we find that the FePt coatings are catalytically active and also make for Janus microswimmers that can be light-actuated and magnetically guided.}, } @article {pmid34069236, year = {2021}, author = {Choe, YW and Sim, SB and Choo, YM}, title = {New Equation for Predicting Pipe Friction Coefficients Using the Statistical Based Entropy Concepts.}, journal = {Entropy (Basel, Switzerland)}, volume = {23}, number = {5}, pages = {}, pmid = {34069236}, issn = {1099-4300}, abstract = {In general, this new equation is significant for designing and operating a pipeline to predict flow discharge. In order to predict the flow discharge, accurate determination of the flow loss due to pipe friction is very important. However, existing pipe friction coefficient equations have difficulties in obtaining key variables or those only applicable to pipes with specific conditions. Thus, this study develops a new equation for predicting pipe friction coefficients using statistically based entropy concepts, which are currently being used in various fields. The parameters in the proposed equation can be easily obtained and are easy to estimate. Existing formulas for calculating pipe friction coefficient requires the friction head loss and Reynolds number. Unlike existing formulas, the proposed equation only requires pipe specifications, entropy value and average velocity. The developed equation can predict the friction coefficient by using the well-known entropy, the mean velocity and the pipe specifications. The comparison results with the Nikuradse's experimental data show that the R2 and RMSE values were 0.998 and 0.000366 in smooth pipe, and 0.979 to 0.994 or 0.000399 to 0.000436 in rough pipe, and the discrepancy ratio analysis results show that the accuracy of both results in smooth and rough pipes is very close to zero. The proposed equation will enable the easier estimation of flow rates.}, } @article {pmid34064079, year = {2021}, author = {Zhou, T and Chen, B and Liu, H}, title = {Study of the Performance of a Novel Radiator with Three Inlets and One Outlet Based on Topology Optimization.}, journal = {Micromachines}, volume = {12}, number = {6}, pages = {}, pmid = {34064079}, issn = {2072-666X}, abstract = {In recent years, in order to obtain a radiator with strong heat exchange capacity, researchers have proposed a lot of heat exchangers to improve heat exchange capacity significantly. However, the cooling abilities of heat exchangers designed by traditional design methods is limited even if the geometric parameters are optimized at the same time. However, using topology optimization to design heat exchangers can overcome this design limitation. Furthermore, researchers have used topology optimization theory to designed one-to-one and many-to-many inlet and outlet heat exchangers because it can effectively increase the heat dissipation rate. In particular, it can further decrease the hot-spot temperature for many-to-many inlet and outlet heat exchangers. Therefore, this article proposes novel heat exchangers with three inlets and one outlet designed by topology optimization to decrease the fluid temperature at the outlet. Subsequently, the effect of the channel depth on the heat exchanger design is also studied. The results show that the type of exchanger varies with the channel depth, and there exists a critical depth value for obtaining the minimum substrate temperature difference. Then, the flow and heat transfer performance of the heat exchangers are numerically investigated. The numerical results show that the heat exchanger derived by topology optimization with the minimum temperature difference as the goal (Model-2) is the best design for flow and heat transfer performance compared to other heat sink designs, including the heat exchanger derived by topology optimization having the average temperature as the goal (Model-1) and conventional straight channels (Model-3). The temperature difference of Model-1 can be reduced by 37.5%, and that of Model-2 can be decreased by 62.5% compared to Model-3. Compared with Model-3, the thermal resistance of Model-1 can be reduced by 21.86%, while that of Model-2 can be decreased by 47.99%. At room temperature, we carried out the forced convention experimental test for Model-2 to measure its physical parameters (temperature, pressure drop) to verify the numerical results. The error of the average wall temperature between experimental results and simulation results is within 2.6 K, while that of the fluid temperature between the experimental and simulation results is within 1.4 K, and the maximum deviation of the measured Nu and simulated Nu was less than 5%. This indicated that the numerical results agreed well with the experimental results.}, } @article {pmid34062924, year = {2021}, author = {Gu, B and Adjiman, CS and Xu, XY}, title = {Correlations for Concentration Polarization and Pressure Drop in Spacer-Filled RO Membrane Modules Based on CFD Simulations.}, journal = {Membranes}, volume = {11}, number = {5}, pages = {}, pmid = {34062924}, issn = {2077-0375}, support = {na//BP International Centre for Advanced Materials (BP-ICAM)/ ; }, abstract = {Empirical correlations for mass transfer coefficient and friction factor are often used in process models for reverse osmosis (RO) membrane systems. These usually involve four dimensionless groups, namely Reynolds number (Re), Sherwood number (Sh), friction factor (f), and Schmidt number (Sc), with the associated coefficients and exponents being obtained by fitting to experimental data. However, the range of geometric and operating conditions covered by the experiments is often limited. In this study, new dimensionless correlations for concentration polarization (CP) modulus and friction factor are presented, which are obtained by dimensional analysis and using simulation data from computational fluid dynamics (CFD). Two-dimensional CFD simulations are performed on three configurations of spacer-filled channels with 76 combinations of operating and geometric conditions for each configuration, covering a broad range of conditions encountered in RO membrane systems. Results obtained with the new correlations are compared with those from existing correlations in the literature. There is good consistency in the predicted CP with mean discrepancies less than 6%, but larger discrepancies for pressure gradient are found among the various friction factor correlations. Furthermore, the new correlations are implemented in a process model with six spiral wound modules in series and the predicted recovery, pressure drop, and specific energy consumption are compared with a reference case obtained by ROSA (Reverse Osmosis System Analysis, The Dow Chemical Company). Differences in predicted recovery and pressure drop are up to 5% and 83%, respectively, highlighting the need for careful selection of correlations when using predictive models in process design. Compared to existing mass transfer correlations, a distinct advantage of our correlations for CP modulus is that they can be directly used to estimate the impact of permeate flux on CP at a membrane surface without having to resort to the film theory.}, } @article {pmid34059714, year = {2021}, author = {Pang, M and Zhang, T and Guo, Y and Zhang, L}, title = {Re-crushing process and non-Darcian seepage characteristics of broken coal medium in coal mine water inrush.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {11380}, pmid = {34059714}, issn = {2045-2322}, support = {51774234//Study on the Mechanism of Water-Gas Coupling Fracture Expansion and Ultrasonic Characteristics of Coal Rock Mass in Drilling Holes/ ; 2021JM-390//Fracture Evolution and Water-Gas Coupled Permeability Mechanism of Coal Body Around Extraction Borehole/ ; }, abstract = {The initiation process of the mine water inrush accident, the essence of this process is the sudden change of the seepage state of the broken coal medium under pressure and the instability of the skeleton. In order to study the re-crushing mechanism and seepage characteristics of the broken coal medium under load, a set of three-axis seepage system was designed independently. Using the steady-state infiltration method, multiple flow factors under different particle size combinations and different stress conditions of the broken coal medium were obtained. The results of the study indicate: in one hand, the reduction of the porosity of the broken coal medium will cause the flow channel to be rebuilt, and the sudden change of flow rate will directly lead to the non-Darcian flow behavior. The early stage of compaction mainly affects the permeability k value, and the later stage of compaction mainly affects the non-Darcian β value; On the other hand, the seepage throat in the broken coal medium may have a sharp increase in its flow rate, leading to a sudden change in the flow pattern. The critical Reynolds number is also used to determine whether non-Darcian flow is formed, and its value in the water inrush system is about 40-133; at the same time, the non-Darcian flow in the broken coal medium conforms to the Forchheimer-type flow law. By analyzing the dependence relationship between factors, a seepage factor representation algebraic relationship suitable for Forchheimer type non-Darcian flow of broken coal medium is given, which can be used as a calculation basis in the prevention and treatment of mine water inrush accidents.}, } @article {pmid34056212, year = {2021}, author = {Agarwal, JR and Torres, CF and Shah, S}, title = {Development of Dimensionless Parameters and Groups of Heat and Mass Transfer to Predict Wax Deposition in Crude Oil Pipelines.}, journal = {ACS omega}, volume = {6}, number = {16}, pages = {10578-10591}, pmid = {34056212}, issn = {2470-1343}, abstract = {A new methodology has been developed for analyzing heat and mass transfer to predict wax deposition in crude oil pipelines using the law of the wall dimensionless parameters. A set of physically meaningful dimensionless groups and parameters has laid a strong foundation behind the proposed methodology. The paper presents a discussion regarding the development of scale-up correlations from laboratory scale to field scale, considering the combination of both analytical groups and empirical correlations. Data from previous literature studies were employed for determining realistic values for the developed parameters and scale-up correlations. The utilization of new dimensionless scale-up parameters indicated that the wax deposition in crude oil pipelines is independent of the Reynolds number and the inner diameter of the pipeline. It further indicates that wax deposition in crude oil pipelines is mainly dependent on the heat transfer process and not on the shear reduction process. The dimensionless technique developed here can be utilized for determining the optimum pipe size and pigging frequencies to reduce and mitigate the effect of the wax deposition process.}, } @article {pmid34050744, year = {2021}, author = {Ford, MP and Santhanakrishnan, A}, title = {Closer Appendage Spacing Augments Metachronal Swimming Speed by Promoting Tip Vortex Interactions.}, journal = {Integrative and comparative biology}, volume = {61}, number = {5}, pages = {1608-1618}, doi = {10.1093/icb/icab112}, pmid = {34050744}, issn = {1557-7023}, mesh = {Animals ; Biomechanical Phenomena ; *Extremities ; Hydrodynamics ; Invertebrates ; *Swimming ; }, abstract = {Numerous species of aquatic invertebrates, including crustaceans, swim by oscillating multiple closely spaced appendages. The coordinated, out-of-phase motion of these appendages, known as "metachronal paddling," has been well-established to improve swimming performance relative to synchronous paddling. Invertebrates employing this propulsion strategy cover a wide range of body sizes and shapes, but the ratio of appendage spacing (G) to the appendage length (L) has been reported to lie in a comparatively narrow range of 0.2 < G/L ≤ 0.65. The functional role of G/L on metachronal swimming performance is unknown. We hypothesized that for a given Reynolds number and stroke amplitude, hydrodynamic interactions promoted by metachronal stroke kinematics with small G/L can increase forward swimming speed. We used a dynamically scaled self-propelling robot to comparatively examine swimming performance and wake development of metachronal and synchronous paddling under varying G/L, phase lag, and stroke amplitude. G/L was varied from 0.4 to 1.5, with the expectation that when G/L is large, there should be no performance difference between metachronal and synchronous paddling due to a lack of interaction between vortices that form on the appendages. Metachronal stroking at nonzero phase lag with G/L in the biological range produced faster swimming speeds than synchronous stroking. As G/L increased and as stroke amplitude decreased, the influence of phase lag on the swimming speed of the robot was reduced. For smaller G/L, vortex interactions between adjacent appendages generated a horizontally oriented wake and increased momentum fluxes relative to larger G/L, which contributed to increasing swimming speed. We find that while metachronal motion augments swimming performance for closely spaced appendages (G/L <1), moderately spaced appendages (1.0 ≤ G/L ≤ 1.5) can benefit from the metachronal motion only when the stroke amplitude is large.}, } @article {pmid34035439, year = {2021}, author = {Shankar, BM and Shivakumara, IS}, title = {Benchmark solution for the stability of plane Couette flow with net throughflow.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {10901}, pmid = {34035439}, issn = {2045-2322}, abstract = {This paper investigates the stability of an incompressible viscous fluid flow between relatively moving horizontal parallel plates in the presence of a uniform vertical throughflow. A linear stability analysis has been performed by employing the method of normal modes and the resulting stability equation is solved numerically using the Chebyshev collocation method. Contrary to the stability of plane Couette flow (PCF) to small disturbances for all values of the Reynolds number in the absence of vertical throughflow, it is found that PCF becomes unstable owing to the change in the sign of growth rate depending on the magnitude of throughflow. The critical Reynolds number triggering the instability is computed for different values of throughflow dependent Reynolds number and it is shown that throughflow instills both stabilizing and destabilizing effect on the base flow. It is seen that the direction of throughflow has no influence on the stability of fluid flow. A comparative study between plane Poiseuille flow and PCF has also been carried out and the similarities and differences are highlighted.}, } @article {pmid34034247, year = {2021}, author = {Kasoju, VT and Santhanakrishnan, A}, title = {Pausing after clap reduces power required to fling wings apart at low Reynolds number.}, journal = {Bioinspiration & biomimetics}, volume = {16}, number = {5}, pages = {}, doi = {10.1088/1748-3190/ac050a}, pmid = {34034247}, issn = {1748-3190}, mesh = {Animals ; Biomechanical Phenomena ; *Flight, Animal ; Insecta ; Models, Biological ; *Thysanoptera ; Wings, Animal ; }, abstract = {The smallest flying insects, such as thrips (body length < 2 mm), are challenged with needing to move in air at a chord-based Reynolds number (Rec) of the order of 10. Pronounced viscous dissipation at such a low Recrequires considerable energetic expenditure for tiny insects to stay aloft. Thrips flap their densely bristled wings at large stroke amplitudes, bringing both wings in close proximity to each other at the end of upstroke ('clap') and moving their wings apart at the start of downstroke ('fling'). From high-speed videos of free take-off flights of thrips, we observed that their forewings remain clapped for approximately 10% of the wingbeat cycle before the start of downstroke (fling stroke). We sought to examine if there are aerodynamic advantages associated with pausing wing motion after upstroke (clap stroke) and before downstroke (fling stroke) at Rec= 10. A dynamically scaled robotic clap and fling platform was used to measure lift and drag forces generated by physical models of solid (non-bristled) and bristled wings in single wing and wing pair configurations, for pause times ranging between 0% to 41% of the cycle. For solid and bristled wing pairs, pausing before the start of downstroke (fling stroke) dissipated vorticity generated at the end of upstroke (clap stroke). This resulted in a decrease in the drag coefficient averaged across downstroke (fling stroke) and in turn reduced power requirements. Also, increasing the pause time resulted in a larger decrease in the dimensionless power coefficient for the wing-pair configurations compared to the single-wing configurations. Our findings show that wing-wing interaction observed in the clap and fling motion of tiny insect wings is necessary to realize the aerodynamic benefits of pausing before fling, by reducing the power required to clap and fling for a small compromise in lift.}, } @article {pmid34030500, year = {2021}, author = {Wanzheng, A and Pengfei, Z}, title = {Correction and laboratory investigation for energy loss coefficient of square-edged orifice plate.}, journal = {Science progress}, volume = {104}, number = {2}, pages = {368504211018571}, doi = {10.1177/00368504211018571}, pmid = {34030500}, issn = {2047-7163}, abstract = {A lot of studies have shown that the hydraulic characteristics of orifice plate are mainly controlled by its contraction ratio, but the thickness of square-edged orifice plate also has many impacts on energy loss characteristics. The primary objective of this study was to investigated the effects of square-edged orifice plate thickness on energy loss characteristics. In this paper, the effects of square-edged orifice plate thickness on energy loss characteristics are investigated by numerical simulation using CFD. Orifice plate discharge tunnel is axial symmetric, two dimensional numerical simulations of orifice plate discharge tunnel flow was used. The equation (9) for calculating energy loss coefficient of square-edged orifice plate energy dissipater considering the influence of thickness is proposed. The results of the present research demonstrate that energy loss coefficient decreases with increase of the orifice plate thickness. The results of model experiment are consistence with the results calculated by using rectified equation in present paper. The CFD simulations and Model experiment for the flow through an orifice plate are carried out. For square-edged orifice plate energy dissipater, the relative orifice plate thickness T/D has remarkable impacts on its energy loss coefficient ξ. The Traditional equation (8) is corrected by numerical results. The equation (9) for calculating energy loss coefficient of square-edged orifice plate energy dissipater considering the influence of thickness is proposed and this equation is available in the condition of d/D = 0.4-0.8, T/D = 0.05-0.25, and Re > 105(Re is Reynolds number). Comparing with the physical model experimental data, the relative errors of equation (9) is smaller than 15%.}, } @article {pmid34026737, year = {2021}, author = {Murayama, Y and Nakata, T and Liu, H}, title = {Flexible Flaps Inspired by Avian Feathers Can Enhance Aerodynamic Robustness in low Reynolds Number Airfoils.}, journal = {Frontiers in bioengineering and biotechnology}, volume = {9}, number = {}, pages = {612182}, pmid = {34026737}, issn = {2296-4185}, abstract = {Unlike rigid rotors of drones, bird wings are composed of flexible feathers that can passively deform while achieving remarkable aerodynamic robustness in response to wind gusts. In this study, we conduct an experimental study on the effects of the flexible flaps inspired by the covert of bird wings on aerodynamic characteristics of fixed-wings in disturbances. Through force measurements and flow visualization in a low-speed wind tunnel, it is found that the flexible flaps can suppress the large-scale vortex shedding and hence reduce the fluctuations of aerodynamic forces in a disturbed flow behind an oscillating plate. Our results demonstrate that the stiffness of the flaps strongly affects the aerodynamic performance, and the force fluctuations are observed to be reduced when the deformation synchronizes with the strong vortex generation. The results point out that the simple attachment of the flexible flaps on the upper surface of the wing is an effective method, providing a novel biomimetic design to improve the aerodynamic robustness of small-scale drones with fixed-wings operating in unpredictable aerial environments.}, } @article {pmid34024939, year = {2021}, author = {Chassagne, F and Barbour, MC and Chivukula, VK and Machicoane, N and Kim, LJ and Levitt, MR and Aliseda, A}, title = {The effect of Dean, Reynolds, and Womersley number on the flow in a spherical cavity on a curved round pipe. Part 1. Fluid mechanics in the cavity as a canonical flow representing intracranial aneurysms.}, journal = {Journal of fluid mechanics}, volume = {915}, number = {}, pages = {}, pmid = {34024939}, issn = {0022-1120}, support = {18CDA34110295/AHA/American Heart Association-American Stroke Association/United States ; R01 NS088072/NS/NINDS NIH HHS/United States ; R01 NS105692/NS/NINDS NIH HHS/United States ; R03 NS078539/NS/NINDS NIH HHS/United States ; }, abstract = {Flow in side-wall cerebral aneurysms can be ideally modelled as the combination of flow over a spherical cavity and flow in a curved circular pipe, two canonical flows. Flow in a curved pipe is known to depend on the Dean number De, combining the effects of Reynolds number, Re, and of the curvature along the pipe centreline, κ. Pulsatility in the flow introduces a dependency on the Womersley number Wo. Using stereo PIV measurements, this study investigated the effect of these three key non-dimensional parameters, by modifying pipe curvature (De), flow-rate (Re), and pulsatility frequency (Wo), on the flow patterns in a spherical cavity. A single counter-rotating vortex was observed in the cavity for all values of pipe curvature κ and Re, for both steady and pulsatile inflow conditions. Increasing the pipe curvature impacted both the flow patterns in the pipe and the cavity, by shifting the velocity profile towards the cavity opening and increasing the flow rate into the cavity. The circulation in the cavity was found to collapse well with only the Dean number, for both steady and pulsatile inflows. For pulsatile inflow, the counter-rotating vortex was unstable and the location of its centre over time was impacted by the curvature of the pipe, as well as the Re and the Wo in the freestream. The circulation in the cavity was higher for steady inflow than for the equivalent average Reynolds and Dean number pulsatile inflow, with very limited impact of the Womersley in the range studied.}, } @article {pmid34007926, year = {2021}, author = {Aljabair, S and Ekaid, AL and Ibrahim, SH and Alesbe, I}, title = {Mixed convection in sinusoidal lid driven cavity with non-uniform temperature distribution on the wall utilizing nanofluid.}, journal = {Heliyon}, volume = {7}, number = {5}, pages = {e06907}, pmid = {34007926}, issn = {2405-8440}, abstract = {Mixed convection heat transfer of Cu-water nanofluid in an arc cavity with non-uniform heating has been numerically studied. The top flat moving wall is isothermally cooled at Tc and moved with a constant velocity. While the heated arc stationary wall of the cavity is maintained at a hot temperature Th. FORTRAN code is used to solve the mass, momentum, and energy equations in dimensionless form with suitable boundary conditions. In this study, the Reynolds number changed from 1 to 2000, and the Rayleigh number changed from 0 to 10[7]. Also, the range of nanoparticles volume fraction extends from ϕ = 0 to 0.07. Stream vorticity method selected for the discretization of flow and energy equations. The present results are compared with the previous results for the validation part, where the results found a good agreement with the others works. The isotherms are regulated near the arc-shape wall causing a steep temperature gradient at these regions and the local and average heat transfer rate increases with increased volume fraction or Reynolds number or Rayleigh number. Finally, Correlation equations of the average Nusselt number from numerical results are presented.}, } @article {pmid34006011, year = {2021}, author = {Fouxon, I and Feinberg, J and Mond, M}, title = {Linear and nonlinear hydromagnetic stability in laminar and turbulent flows.}, journal = {Physical review. E}, volume = {103}, number = {4-1}, pages = {043104}, doi = {10.1103/PhysRevE.103.043104}, pmid = {34006011}, issn = {2470-0053}, abstract = {We consider the evolution of arbitrarily large perturbations of a prescribed pure hydrodynamical flow of an electrically conducting fluid. We study whether the flow perturbations as well as the generated magnetic fields decay or grow with time and constitute a dynamo process. For that purpose we derive a generalized Reynolds-Orr equation for the sum of the kinetic energy of the hydrodynamic perturbation and the magnetic energy. The flow is confined in a finite volume so the normal component of the velocity at the boundary is zero. The tangential component is left arbitrary in contrast with previous works. For the magnetic field we mostly employ the classical boundary conditions where the field extends in the whole space. We establish critical values of hydrodynamic and magnetic Reynolds numbers below which arbitrarily large initial perturbations of the hydrodynamic flow decay. This involves generalization of the Rayleigh-Faber-Krahn inequality for the smallest eigenvalue of an elliptic operator. For high Reynolds number turbulence we provide an estimate of critical magnetic Reynolds number below which arbitrarily large fluctuations of the magnetic field decay.}, } @article {pmid34005982, year = {2021}, author = {Gissinger, JR and Zinchenko, AZ and Davis, RH}, title = {Internal circulation and mixing within tight-squeezing deformable droplets.}, journal = {Physical review. E}, volume = {103}, number = {4-1}, pages = {043106}, doi = {10.1103/PhysRevE.103.043106}, pmid = {34005982}, issn = {2470-0053}, abstract = {The internal flow and mixing properties inside deformable droplets, after reaching the steady state within two types of passive droplet traps, are visualized and analyzed as dynamical systems. The first droplet trap (constriction) is formed by three spheres arranged in an equilateral triangle, while the second consists of two parallel spherocylinders (capsules). The systems are assumed to be embedded in a uniform far-field flow at low Reynolds number, and the steady shapes and interfacial velocities on the drops are generated using the boundary-integral method. The internal velocity field is recovered by solving the internal Dirichlet problem, also via a desingularized boundary-integral method. Calculation of 2D streamlines within planes of symmetry reveals the internal equilibria of the flow. The type of each equilibrium is classified in 3D and their interactions probed using passive tracers and their Poincaré maps. For the two-capsule droplet, saddle points located on orthogonal symmetry planes influence the regular flow within the drop. For the three-sphere droplet, large regions of chaos are observed, embedded with simple periodic orbits. Flow is visualized via passive dyes, using material lines and surfaces. In 2D, solely the interface between two passive interior fluids is advected using an adaptive number of linked tracer particles. The reduction in dimension decreases the number of required tracer points, and also resolves arbitrarily thin filaments, in contrast to backward cell-mapping methods. In 3D, the advection of a material surface, bounded by the droplet interface, is enabled using an adaptive mesh scheme. Off-lattice 3D contour advection allows for highly resolved visualizations of the internal flow and quantification of the associated degree of mixing. Analysis of the time-dependent growth of material surfaces and 3D mixing numbers suggests the three-sphere droplet exhibits superior mixing properties compared to the two-capsule droplet.}, } @article {pmid34005876, year = {2021}, author = {Brahmachary, S and Natarajan, G and Kulkarni, V and Sahoo, N and Ashok, V and Kumar, V}, title = {Role of solution reconstruction in hypersonic viscous computations using a sharp interface immersed boundary method.}, journal = {Physical review. E}, volume = {103}, number = {4-1}, pages = {043302}, doi = {10.1103/PhysRevE.103.043302}, pmid = {34005876}, issn = {2470-0053}, abstract = {This work discusses the development of a sharp interface immersed boundary (IB) method for viscous compressible flows and its assessment for accurate computations of wall shear and heat fluxes in hypersonic flows. The IB method is implemented in an unstructured Cartesian finite-volume (FV) framework and resolves the geometric interface sharply on the nonconformal mesh through direct imposition of boundary conditions employing a local reconstruction approach. The efficacy of the IB-FV solver is investigated for canonical high-speed viscous flows over a range of Mach numbers. The numerical results indicate that the surface pressure and shear stress distributions are computed with reasonable accuracy, whereas surface heat fluxes for aerodynamically blunt configurations are underpredicted. Employing a set of carefully designed experiments and simple diagnostic tools, we probe the possible causes for the underprediction in heat flux. We show that there exist two sources of error-one due to grid resolution and the other due to solution reconstruction, with the latter being more prominent and responsible for the observed underprediction in heat fluxes. Studies reveal that the heat flux estimates are sensitive to the choice of temperature reconstruction and linear interpolations could lead to poor estimates of heat flux. Our investigations conclusively point out the fact that existing polynomial-based reconstruction approaches for sharp interface IB techniques are not necessarily adequate for heat transfer predictions in high Reynolds number hypersonic flows.}, } @article {pmid34001882, year = {2021}, author = {Nguyen, QM and Abouezzi, J and Ristroph, L}, title = {Early turbulence and pulsatile flows enhance diodicity of Tesla's macrofluidic valve.}, journal = {Nature communications}, volume = {12}, number = {1}, pages = {2884}, pmid = {34001882}, issn = {2041-1723}, abstract = {Microfluidics has enabled a revolution in the manipulation of small volumes of fluids. Controlling flows at larger scales and faster rates, or macrofluidics, has broad applications but involves the unique complexities of inertial flow physics. We show how such effects are exploited in a device proposed by Nikola Tesla that acts as a diode or valve whose asymmetric internal geometry leads to direction-dependent fluidic resistance. Systematic tests for steady forcing conditions reveal that diodicity turns on abruptly at Reynolds number [Formula: see text] and is accompanied by nonlinear pressure-flux scaling and flow instabilities, suggesting a laminar-to-turbulent transition that is triggered at unusually low [Formula: see text]. To assess performance for unsteady forcing, we devise a circuit that functions as an AC-to-DC converter, rectifier, or pump in which diodes transform imposed oscillations into directed flow. Our results confirm Tesla's conjecture that diodic performance is boosted for pulsatile flows. The connections between diodicity, early turbulence and pulsatility uncovered here can inform applications in fluidic mixing and pumping.}, } @article {pmid33998932, year = {2021}, author = {Chen, X and Zhang, Y and Wang, J}, title = {Simulation analysis of mixing in passive microchannel with fractal obstacles based on Murray's law.}, journal = {Computer methods in biomechanics and biomedical engineering}, volume = {24}, number = {15}, pages = {1670-1678}, doi = {10.1080/10255842.2021.1906867}, pmid = {33998932}, issn = {1476-8259}, mesh = {Computer Simulation ; Diffusion ; *Fractals ; }, abstract = {In this paper, we designed fractal obstacles according to Murray's law and set them in a microchannel. We study the influence of the numbers of fractal obstacles, channel widths, branch widths, and the distance between fractal obstacles on mixing efficiency. The optimized micromixer has a high mixing efficiency of more than 90% at all velocities. This paper focuses on the analysis of the variation of mixing efficiency and pressure drop in the range of Reynolds number (Re) 0.1-150. The simulation results show that when the fluid velocity is low, the mixing efficiency of the fluids is mainly improved by molecular diffusion, when the fluid velocity is high, the microchannel with fractal obstacles can promote chaotic convection of the fluids and improve the mixing efficiency. The fractal structure based on Murray's law can be widely used in the design of passive micromixer.}, } @article {pmid33998624, year = {2021}, author = {Su, J and Chen, X and Zhu, Y and Hu, G}, title = {Machine learning assisted fast prediction of inertial lift in microchannels.}, journal = {Lab on a chip}, volume = {21}, number = {13}, pages = {2544-2556}, doi = {10.1039/d1lc00225b}, pmid = {33998624}, issn = {1473-0189}, mesh = {Cross-Sectional Studies ; Lab-On-A-Chip Devices ; Machine Learning ; *Microfluidic Analytical Techniques ; Microfluidics ; }, abstract = {Inertial effect has been extensively used in manipulating both engineered particles and biocolloids in microfluidic platforms. The design of inertial microfluidic devices largely relies on precise prediction of particle migration that is determined by the inertial lift acting on the particle. In spite of being the only means to accurately obtain the lift forces, direct numerical simulation (DNS) often consumes high computational cost and even becomes impractical when applied to microchannels with complex geometries. Herein, we proposed a fast numerical algorithm in conjunction with machine learning techniques for the analysis and design of inertial microfluidic devices. A database of inertial lift forces was first generated by conducting DNS over a wide range of operating parameters in straight microchannels with three types of cross-sectional shapes, including rectangular, triangular and semicircular shapes. A machine learning assisted model was then developed to gain the inertial lift distribution, by simply specifying the cross-sectional shape, Reynolds number and particle blockage ratio. The resultant inertial lift was integrated into the Lagrangian tracking method to quickly predict the particle trajectories in two types of microchannels in practical devices and yield good agreement with experimental observations. Our database and the associated codes allow researchers to expedite the development of the inertial microfluidic devices for particle manipulation.}, } @article {pmid33997904, year = {2021}, author = {Garayev, K and Murphy, DW}, title = {Metachronal Swimming of Mantis Shrimp: Kinematics and Interpleopod Vortex Interactions.}, journal = {Integrative and comparative biology}, volume = {61}, number = {5}, pages = {1631-1643}, doi = {10.1093/icb/icab052}, pmid = {33997904}, issn = {1557-7023}, mesh = {Animals ; Biomechanical Phenomena ; *Copepoda ; *Decapoda ; Extremities ; Models, Biological ; Swimming ; }, abstract = {Mantis shrimp swim via metachronal rowing, a pattern in which the pleopods (swimming limbs) stroke sequentially, starting with the last pair and followed by anterior neighbors. A similar swimming pattern is used at various sizes, Reynolds numbers, and advance ratios by diverse organisms including ciliates, ctenophores, copepods, krill, and lobsters. Understanding this type of locomotion is important because it is widespread and may inspire the design of underwater vehicles where efficiency, robustness, and maneuverability are desired. However, detailed measurements of the flow around free-swimming, metachronally rowing organisms are scarce, especially for organisms swimming in a high Reynolds number regime (Re ≥ 104). In this study, we present time-resolved, planar PIV measurements of a swimming peacock mantis shrimp (Odontodactylus scyllarus). Simultaneous kinematics measurements of the animal, which had body and pleopod lengths of 114 and 20 mm, respectively, reveal mean swimming speeds of 0.2-1.9 m s-1 and pleopod beat frequencies of 3.6-13 Hz, corresponding to advance ratios of 0.75-1.84 and body-based Reynolds numbers of 23,000-217,000. Further, the animal's stroke is not purely metachronal, with a long phase lag between initiation of the first and fifth pleopod power strokes. Flow measurements in the sagittal plane show that each stroking pleopod pair creates a posteriorly moving tip vortex which evades destruction by the recovery strokes of other pleopod pairs. The vortex created by the anteriormost pleopod pair is the strongest and, owing to the animal's high advance ratio, is intercepted by the power stroke of the posteriormost pleopod pair. The vortex strength increases as a result of this interaction, which may increase swimming speed or efficiency. A relationship for vortex interception by the posterior pleopod is proposed that relates the phase lag between the interacting pleopods to the beat frequency, distance between those pleopods, and speed of the vortex relative to the animal. We describe this interaction with a novel parameter called the interpleopod vortex phase matching Strouhal number StIVPM which is equal to the phase lag between interacting pleopods. This new nondimensional parameter may be useful in predicting the conditions where a constructive interaction may occur in other species or in physical models. Finally, we relate the advance ratio to the Reynolds number ratio, the ratio between the body-based Reynolds number and the pleopod-based Reynolds number. The importance of these parameters in promoting the interpleopod vortex interactions identified here, in dynamically scaled experiments, and in wake signatures behind schooling metachronal swimmers is discussed.}, } @article {pmid33986400, year = {2021}, author = {Mehboudi, A and Yeom, J}, title = {A passive Stokes flow rectifier for Newtonian fluids.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {10182}, pmid = {33986400}, issn = {2045-2322}, abstract = {Non-linear effects of the Navier-Stokes equations disappear under the Stokes regime of Newtonian fluid flows disallowing a flow rectification behavior. Here we show that passive flow rectification of Newtonian fluids is obtainable under the Stokes regime of both compressible and incompressible flows by introducing nonlinearity into the otherwise linear Stokes equations. Asymmetric flow resistances arise in shallow nozzle/diffuser microchannels with deformable ceiling, in which the fluid flow is governed by a non-linear coupled fluid-solid mechanics equation. The proposed model captures the unequal deflection profile of the deformable ceiling depending on the flow direction under the identical applied pressure, permitting a larger flow rate in the nozzle configuration. Ultra-low aspect ratio microchannels sealed by a flexible membrane have been fabricated to demonstrate passive flow rectification for low-Reynolds-number flows (0.001 < Re < 10) of common Newtonian fluids such as water, methanol, and isopropyl alcohol. The proposed rectification mechanism is also extended to compressible flows, leading to the first demonstration of rectifying equilibrium gas flows under the Stokes flow regime. While the maximum rectification ratio experimentally obtained in this work is limited to 1.41, a higher value up to 1.76 can be achieved by optimizing the width profile of the asymmetric microchannels.}, } @article {pmid33976300, year = {2021}, author = {Kazemi, A and Castillo, L and Curet, OM}, title = {Mangrove roots model suggest an optimal porosity to prevent erosion.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {9969}, pmid = {33976300}, issn = {2045-2322}, abstract = {Mangrove swamps are extremely productive ecosystems providing many ecological services in coastal regions. The hydrodynamic interactions of mangrove roots and water flow have been proposed as a key element to mitigate erosion. Several studies reveal that precise prediction of the morphological evolution of coastal areas, in the face of global warming and the consequent sea-level rise, requires an understanding of interactions between root porosity (the fraction of the volume of void space over the total volume), water flows, and sediment transport. Water flows around the mangrove prop roots create a complex energetic process that mixes up sediments and generates a depositional region posterior to the roots. In this work, we investigated the boundary layer behind permeable arrays of cylinders (patch) that represent the mangrove roots to explore the impact of patch porosity on the onset of sediment transport. The flow measurements were performed in a vertical plane along the water depth downstream of the mangrove root models. A high-resolution Particle Image Velocimetry (PIV) was used in a flume to observe the impact of porosity on the mean flow, velocity derivatives, skin friction coefficient, and production of turbulent kinetic energy for Reynolds number of 2500 (based on patch diameter length-scale). Here, we proposed a predictive model for critical velocity for incipient motion that takes into account the mangrove roots porosity and the near-bed turbulence effect. It is found that the patch with the [Formula: see text] porosity, has the maximum critical velocity over which the sediment transport initiates