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ESP: PubMed Auto Bibliography 31 Aug 2024 at 01:30 Created:
Reynolds Number
It is well known that relative size greatly affects how organisms interact with the world. Less well known, at least among biologists, is that at sufficiently small sizes, mechanical interaction with the environment becomes difficult and then virtually impossible. In fluid dynamics, an important dimensionless parameter is the Reynolds Number (abbreviated Re), which is the ratio of inertial to viscous forces affecting the movement of objects in a fluid medium (or the movement of a fluid in a pipe). Since Re is determined mainly by the size of the object (pipe) and the properties (density and viscosity) of the fluid, organisms of different sizes exhibit significantly different Re values when moving through air or water. A fish, swimming at a high ratio of inertial to viscous forces, gives a flick of its tail and then glides for several body lengths. A bacterium, "swimming" in an environment dominated by viscosity, possesses virtually no inertia. When the bacterium stops moving its flagellum, the bacterium "coasts" for about a half of a microsecond, coming to a stop in a distance less than a tenth the diameter of a hydrogen atom. Similarly, the movement of molecules (nutrients toward, wastes away) in the vicinity of a bacterium is dominated by diffusion. Effective stirring — the generation of bulk flow through mechanical means — is impossible at very low Re. An understanding of the constraints imposed by life at low Reynolds numbers is essentially for understanding the prokaryotic biosphere.
Created with PubMed® Query: ( "reynolds number" ) NOT pmcbook NOT ispreviousversion
Citations The Papers (from PubMed®)
RevDate: 2024-08-24
Mathematical analysis of isothermal study of reverse roll coating using Micropolar fluid.
Scientific reports, 14(1):19709.
This article demonstrates a mathematical model and theoretical analysis of the Micropolar fluid in the reverse roll coating process. It is important because micropolar fluids account for the microstructure and microrotation of particles within the fluid. These characteristics are significant for accurately describing the behavior of complex fluids such as polymer solutions, biological fluids, and colloidal suspensions. First, we modeled the flow equations using basic laws of fluid dynamics. The flow equations are made modified using low Reynolds number theory. The simplified equations are solved analytically. The exact expression for velocity and pressure gradient are obtained, while pressure is calculated numerically using Simpson Rule. Graphical depictions are carried out to comprehend the impact of the newly emerged physical constraints. The influence of micropolar and microrotation parameters on the velocity, pressure and pressure gradient are elaborated with the help of different graphs.
Additional Links: PMID-39181970
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@article {pmid39181970,
year = {2024},
author = {Zaman, SU and Hussain, A and Ashraf, K and Sarwar, L and Hussain, F and Altalbe, A and Bekir, A and Muhammad, T},
title = {Mathematical analysis of isothermal study of reverse roll coating using Micropolar fluid.},
journal = {Scientific reports},
volume = {14},
number = {1},
pages = {19709},
pmid = {39181970},
issn = {2045-2322},
support = {(PSAU/2024/01/921063)//Ali Altalbe/ ; },
abstract = {This article demonstrates a mathematical model and theoretical analysis of the Micropolar fluid in the reverse roll coating process. It is important because micropolar fluids account for the microstructure and microrotation of particles within the fluid. These characteristics are significant for accurately describing the behavior of complex fluids such as polymer solutions, biological fluids, and colloidal suspensions. First, we modeled the flow equations using basic laws of fluid dynamics. The flow equations are made modified using low Reynolds number theory. The simplified equations are solved analytically. The exact expression for velocity and pressure gradient are obtained, while pressure is calculated numerically using Simpson Rule. Graphical depictions are carried out to comprehend the impact of the newly emerged physical constraints. The influence of micropolar and microrotation parameters on the velocity, pressure and pressure gradient are elaborated with the help of different graphs.},
}
RevDate: 2024-08-24
Drop Retention and Departure in Adiabatic Shear Flow on Structured Superhydrophobic Surfaces.
Langmuir : the ACS journal of surfaces and colloids [Epub ahead of print].
Drops are retained or held on surfaces due to a retention force exerted on the drop by the surface. This retention force is a function of the surface tension of the liquid, drop geometry, and the contact angle between the drop and the surface. When external or body forces exceed the retention force, the drop begins to move. This work explores the conditions for which drop departure occurs on structured superhydrophobic surfaces in the presence of an applied shear flow. Drop departure is explored for five microstructured superhydrophobic surfaces, one nanostructured carbon nanotube surface and one smooth hydrophobic surface. Surface solid fractions range from 0.05 to 1.00, and measured static contact angles range from 121° to 161°. Droplet volumes of 5, 10, 20, 30, 40, and 50 μL are tested on each surface. For each experiment, increasing air velocity is applied to a droplet placed on a surface until the droplet departs. High-speed imaging is used to track droplet base length, height, cross-section area (as viewed from the side) and advancing/receding contact angles. Measurements of drop advancing and receding contact angles are reported at the point of departure, with increasing contact angle hysteresis observed prior to departure. Contact angle hysteresis is observed to be a good indicator of droplet mobility. Measurements of the average air velocity over the height of the droplet are determined at the point of departure for all conditions. The measured air velocity shows strong dependence on the surface solid fraction, and the required shear flow velocity decreases as the surface solid fraction decreases. This is most pronounced at very low solid fractions. A coefficient of drag for the departing drops in shear flow is calculated and is shown to decrease with increasing Reynolds number.
Additional Links: PMID-39180481
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@article {pmid39180481,
year = {2024},
author = {Lyons, BM and Maynes, D and Crockett, J and Iverson, BD},
title = {Drop Retention and Departure in Adiabatic Shear Flow on Structured Superhydrophobic Surfaces.},
journal = {Langmuir : the ACS journal of surfaces and colloids},
volume = {},
number = {},
pages = {},
doi = {10.1021/acs.langmuir.4c00777},
pmid = {39180481},
issn = {1520-5827},
abstract = {Drops are retained or held on surfaces due to a retention force exerted on the drop by the surface. This retention force is a function of the surface tension of the liquid, drop geometry, and the contact angle between the drop and the surface. When external or body forces exceed the retention force, the drop begins to move. This work explores the conditions for which drop departure occurs on structured superhydrophobic surfaces in the presence of an applied shear flow. Drop departure is explored for five microstructured superhydrophobic surfaces, one nanostructured carbon nanotube surface and one smooth hydrophobic surface. Surface solid fractions range from 0.05 to 1.00, and measured static contact angles range from 121° to 161°. Droplet volumes of 5, 10, 20, 30, 40, and 50 μL are tested on each surface. For each experiment, increasing air velocity is applied to a droplet placed on a surface until the droplet departs. High-speed imaging is used to track droplet base length, height, cross-section area (as viewed from the side) and advancing/receding contact angles. Measurements of drop advancing and receding contact angles are reported at the point of departure, with increasing contact angle hysteresis observed prior to departure. Contact angle hysteresis is observed to be a good indicator of droplet mobility. Measurements of the average air velocity over the height of the droplet are determined at the point of departure for all conditions. The measured air velocity shows strong dependence on the surface solid fraction, and the required shear flow velocity decreases as the surface solid fraction decreases. This is most pronounced at very low solid fractions. A coefficient of drag for the departing drops in shear flow is calculated and is shown to decrease with increasing Reynolds number.},
}
RevDate: 2024-08-23
Compressible turbulent plane channel DNS datasets.
Data in brief, 55:110737 pii:S2352-3409(24)00704-2.
The database contains detailed statistics of compressible turbulent plane channel (TPC) flow, obtained from direct numerical simulation (DNS), with a very-high-order massively parallel solver of the compressible Navier-Stokes equations. It contains datasets for 25 different flow conditions determined by the corresponding HCB friction Reynolds number and centerline Mach number, covering the ranges 100 ⪅ R e τ ★ ⪅ 1000 and 0.3 ⪅ M ¯ CL x ⪅ 2.5 . All calculations are for strictly isothermal wall conditions at temperature T w = 298 K in a medium-size (MB) computational box (8 π δ × 2 δ × 4 π δ where 2 δ is the channel-height). Statistics (moments and pdfs) were collected after the elimination of the transient, and post-processed to create the dataset, which contains only plain text (.txt) space-separated multicolumn files for ease of use. The dataset for each flow-condition is tagged by the values of (R e τ ★ , M ¯ CL x) and is organized in 4 directories: (0) global data files, (1) profiles and budgets (meanflow profiles, velocity-moments up to 6-order, budgets of Reynolds-stresses transport, turbulent fluxes appearing in transport equations for velocity-moments and thermodynamic quantities, correlation coefficients between thermodynamic variables, and skewness and flatness profiles) as a function of the wall-distance, (2) single-variable probability density functions (pdfs) for numerous flow quantities at selected wall-normal distances, and (3) two-variable joint pdfs for numerous couples of flow-quantities at the same selected wall-normal distances.
Additional Links: PMID-39175794
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@article {pmid39175794,
year = {2024},
author = {Gerolymos, GA and Vallet, I},
title = {Compressible turbulent plane channel DNS datasets.},
journal = {Data in brief},
volume = {55},
number = {},
pages = {110737},
doi = {10.1016/j.dib.2024.110737},
pmid = {39175794},
issn = {2352-3409},
abstract = {The database contains detailed statistics of compressible turbulent plane channel (TPC) flow, obtained from direct numerical simulation (DNS), with a very-high-order massively parallel solver of the compressible Navier-Stokes equations. It contains datasets for 25 different flow conditions determined by the corresponding HCB friction Reynolds number and centerline Mach number, covering the ranges 100 ⪅ R e τ ★ ⪅ 1000 and 0.3 ⪅ M ¯ CL x ⪅ 2.5 . All calculations are for strictly isothermal wall conditions at temperature T w = 298 K in a medium-size (MB) computational box (8 π δ × 2 δ × 4 π δ where 2 δ is the channel-height). Statistics (moments and pdfs) were collected after the elimination of the transient, and post-processed to create the dataset, which contains only plain text (.txt) space-separated multicolumn files for ease of use. The dataset for each flow-condition is tagged by the values of (R e τ ★ , M ¯ CL x) and is organized in 4 directories: (0) global data files, (1) profiles and budgets (meanflow profiles, velocity-moments up to 6-order, budgets of Reynolds-stresses transport, turbulent fluxes appearing in transport equations for velocity-moments and thermodynamic quantities, correlation coefficients between thermodynamic variables, and skewness and flatness profiles) as a function of the wall-distance, (2) single-variable probability density functions (pdfs) for numerous flow quantities at selected wall-normal distances, and (3) two-variable joint pdfs for numerous couples of flow-quantities at the same selected wall-normal distances.},
}
RevDate: 2024-08-22
Analytical and computational studies predict negligible risk of cell death from eddy generation off flat surfaces in cell culture flow systems.
Frontiers in bioengineering and biotechnology, 12:1340653.
Cell-based therapies represent the current frontier of biomedical innovations, with the technologies required underpinning treatments as broad as CAR-T cell therapies, stem cell treatments, genetic therapies and mRNA manufacture. A key bottleneck in the manufacturing process for each of these lies in the expansion of cells within a bioreactor vessel, requiring by far the greatest share of time for what are often time-critical therapies. While various designs, culture feeding and mixing methods are employed in these bioreactors, a common concern among manufacturers and researchers lies in whether shear stresses generated by culture media flow will damage cells and inhibit expansion. This study develops an analytical tool to link macro-scale measures of flow to risk of cell death using relationships with eddy size and dissipation rates, from eddies generated off flat surfaces. This analytical tool was then employed using computational fluid dynamics (CFD) to replicate a range of generic bioreactor geometries and flow conditions. We found that no combination of flow condition or design parameter was predicted by the tool to cause cell death within eddies, indicating negligible risk of cell death due to eddy formation within cell culture systems. While this requires experimental validation, and does not apply when cells are expanded using microcarriers, this tool nonetheless provides reassurance and accessible prediction of bioreactor design parameters that could result in cell death. Finally, our findings show that bioreactor design can be tailored such that the shear stress stimulation of cells can be selectively altered through small changes in flow rate.
Additional Links: PMID-39170061
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@article {pmid39170061,
year = {2024},
author = {Morley, EJ and Brockett, CL and Verbruggen, SW},
title = {Analytical and computational studies predict negligible risk of cell death from eddy generation off flat surfaces in cell culture flow systems.},
journal = {Frontiers in bioengineering and biotechnology},
volume = {12},
number = {},
pages = {1340653},
pmid = {39170061},
issn = {2296-4185},
abstract = {Cell-based therapies represent the current frontier of biomedical innovations, with the technologies required underpinning treatments as broad as CAR-T cell therapies, stem cell treatments, genetic therapies and mRNA manufacture. A key bottleneck in the manufacturing process for each of these lies in the expansion of cells within a bioreactor vessel, requiring by far the greatest share of time for what are often time-critical therapies. While various designs, culture feeding and mixing methods are employed in these bioreactors, a common concern among manufacturers and researchers lies in whether shear stresses generated by culture media flow will damage cells and inhibit expansion. This study develops an analytical tool to link macro-scale measures of flow to risk of cell death using relationships with eddy size and dissipation rates, from eddies generated off flat surfaces. This analytical tool was then employed using computational fluid dynamics (CFD) to replicate a range of generic bioreactor geometries and flow conditions. We found that no combination of flow condition or design parameter was predicted by the tool to cause cell death within eddies, indicating negligible risk of cell death due to eddy formation within cell culture systems. While this requires experimental validation, and does not apply when cells are expanded using microcarriers, this tool nonetheless provides reassurance and accessible prediction of bioreactor design parameters that could result in cell death. Finally, our findings show that bioreactor design can be tailored such that the shear stress stimulation of cells can be selectively altered through small changes in flow rate.},
}
RevDate: 2024-08-21
Analytical solution for MHD nanofluid flow over a porous wedge with melting heat transfer.
Heliyon, 10(15):e34888.
This study employs the Hybrid Analytical-Numerical (HAN) method to investigate steady two-dimensional magnetohydrodynamic (MHD) nanofluid flow over a permeable wedge. Analyzing hyperbolic tangent nanofluid flow, the governing time-independent partial differential equations (PDEs) for continuity, momentum, energy, and concentration transform into a set of nonlinear third-order coupled ordinary differential equations (ODEs) through similarity transformations. These ODEs encompass critical parameters such as Lewis and Prandtl numbers, Brownian diffusion, Weissenberg number, thermophoresis, Dufour and Soret numbers, magnetic field strength, thermal radiation, power law index, and medium permeability. The study explores how variations in these parameters impact the velocity field, skin friction coefficient, Nusselt, and Sherwood numbers. Noteworthy findings include the sensitivity of fluid velocity to parameters like Weissenberg number, power law index, wedge angle, magnetic field strength, permeability, and melting heat transfer. The skin friction coefficient experiences a significant increase with specific parameter changes, while Nusselt and Sherwood numbers remain relatively constant. The local Reynolds number significantly affects Nusselt and Sherwood numbers, with a less pronounced impact on the skin friction coefficient. The study's uniqueness lies in employing the analytical HAN method and extracting recent insights from the results.
Additional Links: PMID-39166020
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@article {pmid39166020,
year = {2024},
author = {Ahmadi Azar, A and Jalili, P and Poolaei Moziraji, Z and Jalili, B and Domiri Ganji, D},
title = {Analytical solution for MHD nanofluid flow over a porous wedge with melting heat transfer.},
journal = {Heliyon},
volume = {10},
number = {15},
pages = {e34888},
pmid = {39166020},
issn = {2405-8440},
abstract = {This study employs the Hybrid Analytical-Numerical (HAN) method to investigate steady two-dimensional magnetohydrodynamic (MHD) nanofluid flow over a permeable wedge. Analyzing hyperbolic tangent nanofluid flow, the governing time-independent partial differential equations (PDEs) for continuity, momentum, energy, and concentration transform into a set of nonlinear third-order coupled ordinary differential equations (ODEs) through similarity transformations. These ODEs encompass critical parameters such as Lewis and Prandtl numbers, Brownian diffusion, Weissenberg number, thermophoresis, Dufour and Soret numbers, magnetic field strength, thermal radiation, power law index, and medium permeability. The study explores how variations in these parameters impact the velocity field, skin friction coefficient, Nusselt, and Sherwood numbers. Noteworthy findings include the sensitivity of fluid velocity to parameters like Weissenberg number, power law index, wedge angle, magnetic field strength, permeability, and melting heat transfer. The skin friction coefficient experiences a significant increase with specific parameter changes, while Nusselt and Sherwood numbers remain relatively constant. The local Reynolds number significantly affects Nusselt and Sherwood numbers, with a less pronounced impact on the skin friction coefficient. The study's uniqueness lies in employing the analytical HAN method and extracting recent insights from the results.},
}
RevDate: 2024-08-21
Deciphering the Evolution of Inertial Migration in Serpentine Channels.
Analytical chemistry [Epub ahead of print].
Serpentine channels coupling inertial and secondary flows enable effective particle focusing and separation, showing great potential in clinical diagnostics and drug screening. However, the nonsteady secondary flows in the serpentine channel make the evolution of inertial migration unclear, hindering the development and application of the serpentine channel. Herein, to refine the inertial migration mechanism, we established a model with varying curvature ratios to study the effect of secondary flow on particle migration in the serpentine channel. This method used direct numerical simulation (DNS) to calculate inertial lift, mapped the inertial lift to cross sections of the serpentine channel, and deciphered the inertial migration by using the Lagrangian particle tracking (LPT) method. The inertial migration of microparticles is experimentally investigated to validate the established numerical model. The results indicate that particle migration in serpentine channels follows a two-stage migration. An increase in secondary flow accelerates the second stage of the migration process while slowing the first stage process. Subsequently, we investigated the effects of different parameters, including Reynolds number, aspect ratio, and blockage ratio, on the equilibrium positions of particles, providing guidelines for the high-resolution separation of particles. Taking flow resistance into account, the dimensionless study makes the separation of arbitrary-sized particles possible. This work reveals the migration mechanism in serpentine channels, paving the way for the inertial separation of the particles.
Additional Links: PMID-39165174
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@article {pmid39165174,
year = {2024},
author = {Liu, Y and Zhang, J and Peng, X and Yan, S},
title = {Deciphering the Evolution of Inertial Migration in Serpentine Channels.},
journal = {Analytical chemistry},
volume = {},
number = {},
pages = {},
doi = {10.1021/acs.analchem.4c03474},
pmid = {39165174},
issn = {1520-6882},
abstract = {Serpentine channels coupling inertial and secondary flows enable effective particle focusing and separation, showing great potential in clinical diagnostics and drug screening. However, the nonsteady secondary flows in the serpentine channel make the evolution of inertial migration unclear, hindering the development and application of the serpentine channel. Herein, to refine the inertial migration mechanism, we established a model with varying curvature ratios to study the effect of secondary flow on particle migration in the serpentine channel. This method used direct numerical simulation (DNS) to calculate inertial lift, mapped the inertial lift to cross sections of the serpentine channel, and deciphered the inertial migration by using the Lagrangian particle tracking (LPT) method. The inertial migration of microparticles is experimentally investigated to validate the established numerical model. The results indicate that particle migration in serpentine channels follows a two-stage migration. An increase in secondary flow accelerates the second stage of the migration process while slowing the first stage process. Subsequently, we investigated the effects of different parameters, including Reynolds number, aspect ratio, and blockage ratio, on the equilibrium positions of particles, providing guidelines for the high-resolution separation of particles. Taking flow resistance into account, the dimensionless study makes the separation of arbitrary-sized particles possible. This work reveals the migration mechanism in serpentine channels, paving the way for the inertial separation of the particles.},
}
RevDate: 2024-08-20
Dynamics of Purcell-type microswimmers with active-elastic joints.
Physical review. E, 110(1-1):014207.
Purcell's planar three-link microswimmer is a classic model of swimming in low-Reynolds-number fluid, inspired by motion of flagellated microorganisms. Many works analyzed this model, assuming that the two joint angles are directly prescribed in phase-shifted periodic inputs. In this work, we study a more realistic scenario by considering an extension of this model which accounts for joints' elasticity and mechanical actuation of periodic torques so that the joint angles are dynamically evolving. Numerical analysis of the swimmer's dynamics reveals multiplicity of periodic solutions, depending on parameters of the inputs-frequency and amplitude of excitation, joints' stiffness ratio, as well as joint's activation. We numerically study swimming direction reversal, as well as bifurcations, stability transitions, and symmetry breaking of the periodic solutions, which represent the effect of buckling instability observed in swimming microorganisms. The results demonstrate that this variant of Purcell's simple model displays rich nonlinear dynamic behavior with actuated-elastic joints. Similar results are also obtained when studying an extended model of a six-link microswimmer.
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@article {pmid39160957,
year = {2024},
author = {Zigelman, A and Ben Zvi, G and Or, Y},
title = {Dynamics of Purcell-type microswimmers with active-elastic joints.},
journal = {Physical review. E},
volume = {110},
number = {1-1},
pages = {014207},
doi = {10.1103/PhysRevE.110.014207},
pmid = {39160957},
issn = {2470-0053},
abstract = {Purcell's planar three-link microswimmer is a classic model of swimming in low-Reynolds-number fluid, inspired by motion of flagellated microorganisms. Many works analyzed this model, assuming that the two joint angles are directly prescribed in phase-shifted periodic inputs. In this work, we study a more realistic scenario by considering an extension of this model which accounts for joints' elasticity and mechanical actuation of periodic torques so that the joint angles are dynamically evolving. Numerical analysis of the swimmer's dynamics reveals multiplicity of periodic solutions, depending on parameters of the inputs-frequency and amplitude of excitation, joints' stiffness ratio, as well as joint's activation. We numerically study swimming direction reversal, as well as bifurcations, stability transitions, and symmetry breaking of the periodic solutions, which represent the effect of buckling instability observed in swimming microorganisms. The results demonstrate that this variant of Purcell's simple model displays rich nonlinear dynamic behavior with actuated-elastic joints. Similar results are also obtained when studying an extended model of a six-link microswimmer.},
}
RevDate: 2024-08-20
Orientational order and topological defects in a dilute solutions of rodlike polymers at low Reynolds number.
Physical review. E, 110(1-2):015104.
The relationship between the polymer orientation and the chaotic flow, in a dilute solution of rigid rodlike polymers at low Reynolds number, is investigated by means of direct numerical simulations. It is found that the rods tend to align with the velocity field in order to minimize the friction with the solvent fluid, while regions of rotational disorder are related to strong vorticity gradients, and therefore to the chaotic flow. The "turbulent-like" behavior of the system is therefore associated with the emergence and interaction of topological defects of the mean director field, similarly to active nematic turbulence. The analysis has been carried out in both two and three spatial dimensions.
Additional Links: PMID-39160917
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@article {pmid39160917,
year = {2024},
author = {Puggioni, L and Musacchio, S},
title = {Orientational order and topological defects in a dilute solutions of rodlike polymers at low Reynolds number.},
journal = {Physical review. E},
volume = {110},
number = {1-2},
pages = {015104},
doi = {10.1103/PhysRevE.110.015104},
pmid = {39160917},
issn = {2470-0053},
abstract = {The relationship between the polymer orientation and the chaotic flow, in a dilute solution of rigid rodlike polymers at low Reynolds number, is investigated by means of direct numerical simulations. It is found that the rods tend to align with the velocity field in order to minimize the friction with the solvent fluid, while regions of rotational disorder are related to strong vorticity gradients, and therefore to the chaotic flow. The "turbulent-like" behavior of the system is therefore associated with the emergence and interaction of topological defects of the mean director field, similarly to active nematic turbulence. The analysis has been carried out in both two and three spatial dimensions.},
}
RevDate: 2024-08-14
Performance optimization of a DLD microfluidic device for separating deformable CTCs.
Electrophoresis [Epub ahead of print].
Deterministic lateral displacement (DLD) microfluidic devices work based on the streamlines created by an array of micro-posts. The configuration of pillars alters the isolation efficiency of these devices. The present paper optimizes the performance of a DLD device for isolating deformable circulating tumor cells. The input variables include cell diameter (d), Young's modulus (E s ${E}_s$), Reynolds number (Re), and tan θ, where θ is the tilted angle of micro-posts. The output, which is the response of the system, is DLD. The numerical simulation results are employed to optimize the device using the response surface method, leading to the proposition of a correlation to estimate DLD as a function of input variables. It is demonstrated that the maximum and minimum impacts on cell lateral displacement correspond to E s ${E}_s$ and Re, respectively.
Additional Links: PMID-39140230
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@article {pmid39140230,
year = {2024},
author = {Mohammadali, R and Bayareh, M and Nadooshan, AA},
title = {Performance optimization of a DLD microfluidic device for separating deformable CTCs.},
journal = {Electrophoresis},
volume = {},
number = {},
pages = {},
doi = {10.1002/elps.202400136},
pmid = {39140230},
issn = {1522-2683},
abstract = {Deterministic lateral displacement (DLD) microfluidic devices work based on the streamlines created by an array of micro-posts. The configuration of pillars alters the isolation efficiency of these devices. The present paper optimizes the performance of a DLD device for isolating deformable circulating tumor cells. The input variables include cell diameter (d), Young's modulus (E s ${E}_
s$), Reynolds number (Re), and tan θ, where θ is the tilted angle of micro-posts. The output, which is the response of the system, is DLD. The numerical simulation results are employed to optimize the device using the response surface method, leading to the proposition of a correlation to estimate DLD as a function of input variables. It is demonstrated that the maximum and minimum impacts on cell lateral displacement correspond to E s ${E}_
s$ and Re, respectively.},
}
RevDate: 2024-08-13
Unified framework for laser-induced transient bubble dynamics within microchannels.
Scientific reports, 14(1):18763.
Oscillatory flow in confined spaces is central to understanding physiological flows and rational design of synthetic periodic-actuation based micromachines. Using theory and experiments on oscillating flows generated through a laser-induced cavitation bubble, we associate the dynamic bubble size (fluid velocity) and bubble lifetime to the laser energy supplied-a control parameter in experiments. Employing different channel cross-section shapes, sizes and lengths, we demonstrate the characteristic scales for velocity, time and energy to depend solely on the channel geometry. Contrary to the generally assumed absence of instability in low Reynolds number flows (< 1000), we report a momentary flow distortion that originates due to the boundary layer separation near channel walls during flow deceleration. The emergence of distorted laminar states is characterized using two stages. First the conditions for the onset of instabilities is analyzed using the Reynolds number and Womersley number for oscillating flows. Second the growth and the ability of an instability to prevail is analyzed using the convective time scale of the flow. Our findings inform rational design of microsystems leveraging pulsatile flows via cavitation-powered microactuation.
Additional Links: PMID-39138284
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@article {pmid39138284,
year = {2024},
author = {Nagalingam, N and Korede, V and Irimia, D and Westerweel, J and Padding, JT and Hartkamp, R and Eral, HB},
title = {Unified framework for laser-induced transient bubble dynamics within microchannels.},
journal = {Scientific reports},
volume = {14},
number = {1},
pages = {18763},
pmid = {39138284},
issn = {2045-2322},
support = {16714//Nederlandse Organisatie voor Wetenschappelijk Onderzoek/ ; },
abstract = {Oscillatory flow in confined spaces is central to understanding physiological flows and rational design of synthetic periodic-actuation based micromachines. Using theory and experiments on oscillating flows generated through a laser-induced cavitation bubble, we associate the dynamic bubble size (fluid velocity) and bubble lifetime to the laser energy supplied-a control parameter in experiments. Employing different channel cross-section shapes, sizes and lengths, we demonstrate the characteristic scales for velocity, time and energy to depend solely on the channel geometry. Contrary to the generally assumed absence of instability in low Reynolds number flows (< 1000), we report a momentary flow distortion that originates due to the boundary layer separation near channel walls during flow deceleration. The emergence of distorted laminar states is characterized using two stages. First the conditions for the onset of instabilities is analyzed using the Reynolds number and Womersley number for oscillating flows. Second the growth and the ability of an instability to prevail is analyzed using the convective time scale of the flow. Our findings inform rational design of microsystems leveraging pulsatile flows via cavitation-powered microactuation.},
}
RevDate: 2024-08-12
Microscopic Particle Image Velocimetry Analysis of Multiphase Flow in a Porous Media Micromodel.
ACS omega, 9(31):34070-34080.
Pore-scale oil displacement behavior was investigated in a porous media micromodel using microscopic particle image velocimetry (μPIV). Porous media micromodels consisting of an ordered square array of cylindrical pillars with 50 and 70% porosities were fabricated with photolithography. The oil displacement was performed with the injection of water at flow rates of 37.5, 75, and 150 μL/h. These flow rates correspond to Reynolds number of 1.1 × 10[-2], 2.2 × 10[-2], and 4.4 × 10[-2], respectively in the 50% porous channel, and 1.84 × 10[-3], 3.69 × 10[-3], and 7.38 × 10[-3], respectively in the 70% porous channel. The capillary numbers for these flow rates are 2.18 × 10[-5], 4.36 × 10[-5], and 8.72 × 10[-5], respectively in the 50% porous channel, and 1.56 × 10[-5], 3.12 × 10[-5], and 6.23 × 10[-5], respectively in the 70% porous channel. The micromodel is initially saturated with oil, with the invading water phase following the path of least resistance as it displaces the oil. The μPIV data were used to construct probability density functions (PDFs) which show an initial, nonzero, peak in transverse velocity as the water enters the micromodel. The PDFs broaden with time, indicating that the water is spreading, before retracting to a peak velocity of 0 mm/s, indicating that the water displacement has achieved equilibrium. We developed a model based on conservation of mass to describe the efficiency of the displacement process. All flow conditions demonstrate peak displacement efficiency when the amount of oil phase displacement is ∼9 pore volumes in 50% porous channel and ∼4 pore volumes in 70% porous channel.
Additional Links: PMID-39130567
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@article {pmid39130567,
year = {2024},
author = {Miah, MAK and Ahasan, K and Kingston, TA and Olsen, MG and Juárez, JJ},
title = {Microscopic Particle Image Velocimetry Analysis of Multiphase Flow in a Porous Media Micromodel.},
journal = {ACS omega},
volume = {9},
number = {31},
pages = {34070-34080},
pmid = {39130567},
issn = {2470-1343},
abstract = {Pore-scale oil displacement behavior was investigated in a porous media micromodel using microscopic particle image velocimetry (μPIV). Porous media micromodels consisting of an ordered square array of cylindrical pillars with 50 and 70% porosities were fabricated with photolithography. The oil displacement was performed with the injection of water at flow rates of 37.5, 75, and 150 μL/h. These flow rates correspond to Reynolds number of 1.1 × 10[-2], 2.2 × 10[-2], and 4.4 × 10[-2], respectively in the 50% porous channel, and 1.84 × 10[-3], 3.69 × 10[-3], and 7.38 × 10[-3], respectively in the 70% porous channel. The capillary numbers for these flow rates are 2.18 × 10[-5], 4.36 × 10[-5], and 8.72 × 10[-5], respectively in the 50% porous channel, and 1.56 × 10[-5], 3.12 × 10[-5], and 6.23 × 10[-5], respectively in the 70% porous channel. The micromodel is initially saturated with oil, with the invading water phase following the path of least resistance as it displaces the oil. The μPIV data were used to construct probability density functions (PDFs) which show an initial, nonzero, peak in transverse velocity as the water enters the micromodel. The PDFs broaden with time, indicating that the water is spreading, before retracting to a peak velocity of 0 mm/s, indicating that the water displacement has achieved equilibrium. We developed a model based on conservation of mass to describe the efficiency of the displacement process. All flow conditions demonstrate peak displacement efficiency when the amount of oil phase displacement is ∼9 pore volumes in 50% porous channel and ∼4 pore volumes in 70% porous channel.},
}
RevDate: 2024-08-12
Data analysis of thermal performance and irreversibility of convective flow in porous-wavy channel having triangular obstacle under magnetic field effect.
Heliyon, 10(14):e34580.
Mixed convective nanofluid flow has substantial importance in improvement of thermal performance, and thermal engineering to meet the global energy crisis. In this study, mixed convective nanofluid flow in a porous-wavy channel with an inner heated triangular obstacle under magnetic field effect is numerically examined. Nanofluid within the channel is heated and cooled from its bottom and top wavy-surfaces. A heated triangular cylinder is located at the centerline of the wavy-channel. Finite element method is utilized to solve the non-dimensional governing equations. The code is validated comparing present results with published numerical and experimental results. The response surface method is also implemented to analyze the obtained results and its sensitivity. The numerical results indicate that strength of flow velocity is accelerated with rising Reynolds number, Darcy numbers and inlet-outlet ports length but declined for Hartmann number and volume fraction. Heat transferring rate and heat transfer irreversibility are substantially increased for higher values of Reynolds number, inlet-outlet ports length, Darcy number and nanoparticle volume fraction but a reverse trend is occurred for magnetic field effect. The thermal performance is found significantly improved with simultaneous increment in Re, ϕ, Da and decrement in Ha. Positive sensitivity is achieved for input factors Re, ϕ, Da in computing N u a v while negative sensitivity to Ha. Heat transfer rate is found more sensitive to the impact of Re and ϕ compared to Da and Ha. 45.59 % more heat transmission potentiality is developed for using Al2O3-H2O nanofluid (vol.5 %) instead of using base fluid water. Heat transfer enhancement rate is decreased by 36.22 % due to impact of magnetic field strength. In addition, 84.12 % more heat transferring rate is recorded in presence of triangular obstacle. Moreover, irreversibility components are influenced significantly for the presence of heated triangular obstacle. Bejan number is also found declined for increasing physical parameters. The findings of this investigation may offer a guideline for finding experimental results to design high-performance convective heat exchangers.
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@article {pmid39130463,
year = {2024},
author = {Akhter, R and Ali, MM and Alim, MA},
title = {Data analysis of thermal performance and irreversibility of convective flow in porous-wavy channel having triangular obstacle under magnetic field effect.},
journal = {Heliyon},
volume = {10},
number = {14},
pages = {e34580},
pmid = {39130463},
issn = {2405-8440},
abstract = {Mixed convective nanofluid flow has substantial importance in improvement of thermal performance, and thermal engineering to meet the global energy crisis. In this study, mixed convective nanofluid flow in a porous-wavy channel with an inner heated triangular obstacle under magnetic field effect is numerically examined. Nanofluid within the channel is heated and cooled from its bottom and top wavy-surfaces. A heated triangular cylinder is located at the centerline of the wavy-channel. Finite element method is utilized to solve the non-dimensional governing equations. The code is validated comparing present results with published numerical and experimental results. The response surface method is also implemented to analyze the obtained results and its sensitivity. The numerical results indicate that strength of flow velocity is accelerated with rising Reynolds number, Darcy numbers and inlet-outlet ports length but declined for Hartmann number and volume fraction. Heat transferring rate and heat transfer irreversibility are substantially increased for higher values of Reynolds number, inlet-outlet ports length, Darcy number and nanoparticle volume fraction but a reverse trend is occurred for magnetic field effect. The thermal performance is found significantly improved with simultaneous increment in Re, ϕ, Da and decrement in Ha. Positive sensitivity is achieved for input factors Re, ϕ, Da in computing N u a v while negative sensitivity to Ha. Heat transfer rate is found more sensitive to the impact of Re and ϕ compared to Da and Ha. 45.59 % more heat transmission potentiality is developed for using Al2O3-H2O nanofluid (vol.5 %) instead of using base fluid water. Heat transfer enhancement rate is decreased by 36.22 % due to impact of magnetic field strength. In addition, 84.12 % more heat transferring rate is recorded in presence of triangular obstacle. Moreover, irreversibility components are influenced significantly for the presence of heated triangular obstacle. Bejan number is also found declined for increasing physical parameters. The findings of this investigation may offer a guideline for finding experimental results to design high-performance convective heat exchangers.},
}
RevDate: 2024-08-10
Axisymmetric Slow Rotation of Coaxial Soft/Porous Spheres.
Molecules (Basel, Switzerland), 29(15): pii:molecules29153573.
The steady low-Reynolds-number rotation of a chain of coaxial soft spheres (each with an impermeable hard core covered by a permeable porous layer) about the axis in a viscous fluid is analyzed. The particles may be unequally spaced, and may differ in the permeability and inner and outer radii of the porous surface layer as well as angular velocity. By using a method of boundary collocation, the Stokes and Brinkman equations for the external fluid flow and flow within the surface layers, respectively, are solved semi-analytically. The particle interaction effect increases as the relative gap thickness between adjacent particles or their permeability decreases, which can be significant as the gap thickness approaches zero. A particle's hydrodynamic torque is reduced (its rotation is enhanced) when other particles rotate in the same direction at equivalent or greater angular velocities, but increases (its rotation is hindered) when other particles rotate in the opposite direction at arbitrary angular velocities. For particles with different radii or permeabilities, the particle interaction has a greater effect on smaller or more permeable particles than on larger or less permeable particles. For the rotation of three particles, the presence of the third particle can significantly affect the hydrodynamic torques acting on the other two particles. For the rotation of numerous particles, shielding effects between particles can be substantial. When the permeability of porous layers is low, relative fluid motion is barely felt by the hard cores of the soft particles. The insights gained from this analysis on the effects of interactions among rotating soft particles may be of great importance in many physicochemical applications of colloidal suspensions.
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@article {pmid39124977,
year = {2024},
author = {Chou, YF and Keh, HJ},
title = {Axisymmetric Slow Rotation of Coaxial Soft/Porous Spheres.},
journal = {Molecules (Basel, Switzerland)},
volume = {29},
number = {15},
pages = {},
doi = {10.3390/molecules29153573},
pmid = {39124977},
issn = {1420-3049},
support = {MOST 110-2221-E-002-017-MY3//National Science and Technology Council Taiwan/ ; },
abstract = {The steady low-Reynolds-number rotation of a chain of coaxial soft spheres (each with an impermeable hard core covered by a permeable porous layer) about the axis in a viscous fluid is analyzed. The particles may be unequally spaced, and may differ in the permeability and inner and outer radii of the porous surface layer as well as angular velocity. By using a method of boundary collocation, the Stokes and Brinkman equations for the external fluid flow and flow within the surface layers, respectively, are solved semi-analytically. The particle interaction effect increases as the relative gap thickness between adjacent particles or their permeability decreases, which can be significant as the gap thickness approaches zero. A particle's hydrodynamic torque is reduced (its rotation is enhanced) when other particles rotate in the same direction at equivalent or greater angular velocities, but increases (its rotation is hindered) when other particles rotate in the opposite direction at arbitrary angular velocities. For particles with different radii or permeabilities, the particle interaction has a greater effect on smaller or more permeable particles than on larger or less permeable particles. For the rotation of three particles, the presence of the third particle can significantly affect the hydrodynamic torques acting on the other two particles. For the rotation of numerous particles, shielding effects between particles can be substantial. When the permeability of porous layers is low, relative fluid motion is barely felt by the hard cores of the soft particles. The insights gained from this analysis on the effects of interactions among rotating soft particles may be of great importance in many physicochemical applications of colloidal suspensions.},
}
RevDate: 2024-08-07
Pyramid-Shaped Superhydrophobic Surfaces for Underwater Drag Reduction.
ACS applied materials & interfaces [Epub ahead of print].
Superhydrophobic surfaces hold immense potential in underwater drag reduction. However, as the Reynolds number increases, the drag reduction rate decreases, and it may even lead to a drag increase. The reason lies in the collapse of the air mattress. To address this issue, this paper develops a pyramid-shaped robust superhydrophobic surface with wedged microgrooves, which exhibits a high gas fraction when immersed underwater and good ability to achieve complete spreading and recovery of the air mattress through air replenishment in the case of collapse of the air mattress. Pressure drop tests in a water tunnel confirm that with continuous air injection, the drag reduction reaches 64.8% in laminar flow conditions, substantially greater than 38.4% in the case without air injection, and can achieve 50.8% drag reduction in turbulent flow. This result highlights the potential applications of superhydrophobic surfaces with air mattress recovery for drag reduction.
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@article {pmid39110849,
year = {2024},
author = {Zhang, L and Wan, X and Zhou, X and Cao, Y and Duan, H and Yan, J and Li, H and Lv, P},
title = {Pyramid-Shaped Superhydrophobic Surfaces for Underwater Drag Reduction.},
journal = {ACS applied materials & interfaces},
volume = {},
number = {},
pages = {},
doi = {10.1021/acsami.4c09631},
pmid = {39110849},
issn = {1944-8252},
abstract = {Superhydrophobic surfaces hold immense potential in underwater drag reduction. However, as the Reynolds number increases, the drag reduction rate decreases, and it may even lead to a drag increase. The reason lies in the collapse of the air mattress. To address this issue, this paper develops a pyramid-shaped robust superhydrophobic surface with wedged microgrooves, which exhibits a high gas fraction when immersed underwater and good ability to achieve complete spreading and recovery of the air mattress through air replenishment in the case of collapse of the air mattress. Pressure drop tests in a water tunnel confirm that with continuous air injection, the drag reduction reaches 64.8% in laminar flow conditions, substantially greater than 38.4% in the case without air injection, and can achieve 50.8% drag reduction in turbulent flow. This result highlights the potential applications of superhydrophobic surfaces with air mattress recovery for drag reduction.},
}
RevDate: 2024-08-05
Spacing effects on flows around two square cylinders in staggered arrangement via LBM.
Scientific reports, 14(1):18049.
This study presents a computational analysis of fluid flow characteristics around two staggered arranged square cylinders using the Lattice Boltzmann Method (LBM). With Reynolds number (Re) fixed at 200, numerical simulations explore the influence of varying gap ratios (G) ranging from 0 to 10 times the cylinder size. Emphasis is placed on understanding the impact of cylinders spacing on flow structure mechanisms and induced forces. Investigation of fluid flow parameters includes vorticity behavior, pressure streamlines, and variations in drag and lift coefficients alongside the Strouhal number under different values of G. From the results, four distinct flow patterns emerge: single bluff body flow, flip flopping flow, modulated synchronized flow, and synchronized flow, each exhibiting unique characteristics. This study reveals the strong dependence of fluid forces on G, with low spacing values leading to complex vortex structures and fluctuating forces influenced by jet flow effects. At higher spacing values, proximity effects between cylinders diminish, resulting in a smoother periodic flow. The Strouhal number, average drag force and the rms values of drag and lift force coefficients vary abruptly at narrow gaps and become smooth at higher gap ratios. Unlike the tandem and side-by-side arrangements the staggered cylinders arrangement is found to have significant impact on the pressure variations around both cylinders. Overall, this research could contribute to a comprehensive understanding of staggered cylinder arrangements and their implications for engineering applications.
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@article {pmid39103401,
year = {2024},
author = {Refaie Ali, A and Abbasi, WS and Bibi, B and Rahman, H and Ul Islam, S and Hussain Majeed, A and Ahmad, I},
title = {Spacing effects on flows around two square cylinders in staggered arrangement via LBM.},
journal = {Scientific reports},
volume = {14},
number = {1},
pages = {18049},
pmid = {39103401},
issn = {2045-2322},
abstract = {This study presents a computational analysis of fluid flow characteristics around two staggered arranged square cylinders using the Lattice Boltzmann Method (LBM). With Reynolds number (Re) fixed at 200, numerical simulations explore the influence of varying gap ratios (G) ranging from 0 to 10 times the cylinder size. Emphasis is placed on understanding the impact of cylinders spacing on flow structure mechanisms and induced forces. Investigation of fluid flow parameters includes vorticity behavior, pressure streamlines, and variations in drag and lift coefficients alongside the Strouhal number under different values of G. From the results, four distinct flow patterns emerge: single bluff body flow, flip flopping flow, modulated synchronized flow, and synchronized flow, each exhibiting unique characteristics. This study reveals the strong dependence of fluid forces on G, with low spacing values leading to complex vortex structures and fluctuating forces influenced by jet flow effects. At higher spacing values, proximity effects between cylinders diminish, resulting in a smoother periodic flow. The Strouhal number, average drag force and the rms values of drag and lift force coefficients vary abruptly at narrow gaps and become smooth at higher gap ratios. Unlike the tandem and side-by-side arrangements the staggered cylinders arrangement is found to have significant impact on the pressure variations around both cylinders. Overall, this research could contribute to a comprehensive understanding of staggered cylinder arrangements and their implications for engineering applications.},
}
RevDate: 2024-08-05
Spatiotemporally controlled microvortices provide advanced microfluidic components.
Proceedings of the National Academy of Sciences of the United States of America, 121(33):e2306182121.
Microvortices are emerging components that impart functionality to microchannels by exploiting inertia effects such as high shear stress, effective fluid diffusion, and large pressure loss. Exploring the dynamic generation of vortices further expands the scope of microfluidic applications, including cell stimulation, fluid mixing, and transport. Despite the crucial role of vortices' development within sub-millisecond timescales, previous studies in microfluidics did not explore the modulation of the Reynolds number (Re) in the range of several hundred. In this study, we modulated high-speed flows (54 < [Formula: see text] < 456) within sub-millisecond timescales using a piezo-driven on-chip membrane pump. By applying this method to microchannels with asymmetric geometries, we successfully controlled the spatiotemporal development of vortices, adjusting their behavior in response to oscillatory flow directions. These different vortices induced different pressure losses, imparting the microchannels with direction-dependent flow resistance, mimicking a diode-like behavior. Through precise control of vortex development, we managed to regulate this direction-dependent resistance, enabling the rectification of oscillatory flow resembling a diode and the ability to switch its rectification direction. This component facilitated bidirectional flow control without the need for mechanical valves. Moreover, we demonstrated its application in microfluidic cell pipetting, enabling the isolation of single cells. Consequently, based on modulating high-speed flow, our approach offers precise control over the spatiotemporal development of vortices in microstructures, thereby introducing innovative microfluidic functionalities.
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@article {pmid39102543,
year = {2024},
author = {Saito, M and Arai, F and Yamanishi, Y and Sakuma, S},
title = {Spatiotemporally controlled microvortices provide advanced microfluidic components.},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
volume = {121},
number = {33},
pages = {e2306182121},
doi = {10.1073/pnas.2306182121},
pmid = {39102543},
issn = {1091-6490},
support = {22J23814//MEXT | Japan Society for the Promotion of Science (JSPS)/ ; JPMJFR2157//MEXT | JST | Fusion Oriented REsearch for disruptive Science and Technology (FOREST)/ ; },
abstract = {Microvortices are emerging components that impart functionality to microchannels by exploiting inertia effects such as high shear stress, effective fluid diffusion, and large pressure loss. Exploring the dynamic generation of vortices further expands the scope of microfluidic applications, including cell stimulation, fluid mixing, and transport. Despite the crucial role of vortices' development within sub-millisecond timescales, previous studies in microfluidics did not explore the modulation of the Reynolds number (Re) in the range of several hundred. In this study, we modulated high-speed flows (54 < [Formula: see text] < 456) within sub-millisecond timescales using a piezo-driven on-chip membrane pump. By applying this method to microchannels with asymmetric geometries, we successfully controlled the spatiotemporal development of vortices, adjusting their behavior in response to oscillatory flow directions. These different vortices induced different pressure losses, imparting the microchannels with direction-dependent flow resistance, mimicking a diode-like behavior. Through precise control of vortex development, we managed to regulate this direction-dependent resistance, enabling the rectification of oscillatory flow resembling a diode and the ability to switch its rectification direction. This component facilitated bidirectional flow control without the need for mechanical valves. Moreover, we demonstrated its application in microfluidic cell pipetting, enabling the isolation of single cells. Consequently, based on modulating high-speed flow, our approach offers precise control over the spatiotemporal development of vortices in microstructures, thereby introducing innovative microfluidic functionalities.},
}
RevDate: 2024-08-02
Erratum: An experimental study of the wall-pressure fluctuations beneath low Reynolds number turbulent boundary layers [J. Acoust. Soc. Am. 141, 1257-1268 (2017)].
The Journal of the Acoustical Society of America, 156(2):725.
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@article {pmid39093039,
year = {2024},
author = {Van Blitterswyk, J and Rocha, J},
title = {Erratum: An experimental study of the wall-pressure fluctuations beneath low Reynolds number turbulent boundary layers [J. Acoust. Soc. Am. 141, 1257-1268 (2017)].},
journal = {The Journal of the Acoustical Society of America},
volume = {156},
number = {2},
pages = {725},
doi = {10.1121/10.0028125},
pmid = {39093039},
issn = {1520-8524},
}
RevDate: 2024-07-31
Numerical investigation on the impact of different design arrangements of helical heat exchangers with varying cross-sections utilizing ternary hybrid nanofluids.
Heliyon, 10(14):e34481 pii:S2405-8440(24)10512-9.
Helical tube heat exchangers (HTHE) are commonly used as thermal devices in various thermal engineering applications. A comparative investigation was undertaken to examine several helical tube designs in relation to their potential uses with water and nanofluids. Additionally, employing the ternary hybrid nanofluid (THNF) flow in helical-type heat exchangers to assess the heat transfer and frictional loss is a unique concept, as there is currently no research on this specific application. This study involves analyzing three different design configurations, each of which has three different inlet profiles: round, square, and oval shapes. Hence, a numerical analysis has been conducted on nine cases, each including the same pipe length, helix diameter, and pitch distance. The specified range for the Reynolds number under the water and THNF flow condition is 5000-25000. The results are acquired for both fluids, considering the Nusselt number (Nu), friction factor (f), outlet temperature (T out), and entropy production (S g). Multi-Criteria Decision Making (MCDM) is employed to provide a thorough assessment of the overall performance of the proposed designs. The results have been shown as graphical representations, streamlines and contours where Nusselt number, friction factor and entropy generation have been evaluated. The Nusselt number has a higher value for the oval cross-section, while it reaches its lowest value for the square cross-section. The highest heat transfer rate is got for Design 1 with the oval-shaped case. The friction factor for a circular cross-section HHTE is 48 % higher than the friction factor for a square cross-section profile. In addition, the square shape at a Reynolds number (Re) of 25000 exhibits 5 % less entropy formation compared to the oval shape geometry at a Reynolds number of 5000. The results of MCDM analysis indicate that Design 1, which features a square section, exhibits superior performance. Conversely, Design 2, which incorporates a circular cross-section, demonstrates poor performance. Among the six ternary hybrid nanofluids, the Al2O3+CNT+Graphene nanofluid with a water basis exhibits the greatest Nusselt number.
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@article {pmid39082012,
year = {2024},
author = {Fahad, MK and Hasan, MJ and Ifraj, NF and Chandra Dey, D},
title = {Numerical investigation on the impact of different design arrangements of helical heat exchangers with varying cross-sections utilizing ternary hybrid nanofluids.},
journal = {Heliyon},
volume = {10},
number = {14},
pages = {e34481},
doi = {10.1016/j.heliyon.2024.e34481},
pmid = {39082012},
issn = {2405-8440},
abstract = {Helical tube heat exchangers (HTHE) are commonly used as thermal devices in various thermal engineering applications. A comparative investigation was undertaken to examine several helical tube designs in relation to their potential uses with water and nanofluids. Additionally, employing the ternary hybrid nanofluid (THNF) flow in helical-type heat exchangers to assess the heat transfer and frictional loss is a unique concept, as there is currently no research on this specific application. This study involves analyzing three different design configurations, each of which has three different inlet profiles: round, square, and oval shapes. Hence, a numerical analysis has been conducted on nine cases, each including the same pipe length, helix diameter, and pitch distance. The specified range for the Reynolds number under the water and THNF flow condition is 5000-25000. The results are acquired for both fluids, considering the Nusselt number (Nu), friction factor (f), outlet temperature (T out), and entropy production (S g). Multi-Criteria Decision Making (MCDM) is employed to provide a thorough assessment of the overall performance of the proposed designs. The results have been shown as graphical representations, streamlines and contours where Nusselt number, friction factor and entropy generation have been evaluated. The Nusselt number has a higher value for the oval cross-section, while it reaches its lowest value for the square cross-section. The highest heat transfer rate is got for Design 1 with the oval-shaped case. The friction factor for a circular cross-section HHTE is 48 % higher than the friction factor for a square cross-section profile. In addition, the square shape at a Reynolds number (Re) of 25000 exhibits 5 % less entropy formation compared to the oval shape geometry at a Reynolds number of 5000. The results of MCDM analysis indicate that Design 1, which features a square section, exhibits superior performance. Conversely, Design 2, which incorporates a circular cross-section, demonstrates poor performance. Among the six ternary hybrid nanofluids, the Al2O3+CNT+Graphene nanofluid with a water basis exhibits the greatest Nusselt number.},
}
RevDate: 2024-07-27
Electro-Osmotic Flow and Mass Transfer through a Rough Microchannel with a Modulated Charged Surface.
Micromachines, 15(7): pii:mi15070882.
In this paper, we investigate the electro-osmotic flow (EOF) and mass transfer of a Newtonian fluid propelled by a pressure gradient and alternating current (AC) electric field in a parallel microchannel with sinusoidal roughness and modulated charged surfaces. The two-wall roughness is described by in-phase or out-of-phase sine functions with a small amplitude δ. By employing the method of perturbation expansion, the semi-analytical solutions of the Poisson-Boltzmann (P-B) equation based on the Debye-Hückel approximation and the modified Navier-Stokes (N-S) equation are obtained. The numerical solution of the concentration equation is obtained by the finite difference method. The effects of sinusoidal roughness, modulated charged surface, and the AC electric field on the potential field, velocity field, and concentration field are discussed. Under the influence of the modulated charged surface and sinusoidal roughness, vortices are generated. The velocity oscillates due to the effect of the AC electric field. The results indicate that solute diffusion becomes enhanced when the oscillation Reynolds number is below a specific critical value, and it slows down when the oscillation Reynolds number exceeds this critical value.
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@article {pmid39064393,
year = {2024},
author = {Qing, Y and Wang, J and Li, F},
title = {Electro-Osmotic Flow and Mass Transfer through a Rough Microchannel with a Modulated Charged Surface.},
journal = {Micromachines},
volume = {15},
number = {7},
pages = {},
doi = {10.3390/mi15070882},
pmid = {39064393},
issn = {2072-666X},
support = {11902164//The National Natural Science Foundation of China/ ; },
abstract = {In this paper, we investigate the electro-osmotic flow (EOF) and mass transfer of a Newtonian fluid propelled by a pressure gradient and alternating current (AC) electric field in a parallel microchannel with sinusoidal roughness and modulated charged surfaces. The two-wall roughness is described by in-phase or out-of-phase sine functions with a small amplitude δ. By employing the method of perturbation expansion, the semi-analytical solutions of the Poisson-Boltzmann (P-B) equation based on the Debye-Hückel approximation and the modified Navier-Stokes (N-S) equation are obtained. The numerical solution of the concentration equation is obtained by the finite difference method. The effects of sinusoidal roughness, modulated charged surface, and the AC electric field on the potential field, velocity field, and concentration field are discussed. Under the influence of the modulated charged surface and sinusoidal roughness, vortices are generated. The velocity oscillates due to the effect of the AC electric field. The results indicate that solute diffusion becomes enhanced when the oscillation Reynolds number is below a specific critical value, and it slows down when the oscillation Reynolds number exceeds this critical value.},
}
RevDate: 2024-07-26
Laser Ablating Biomimetic Periodic Array Fish Scale Surface for Drag Reduction.
Biomimetics (Basel, Switzerland), 9(7): pii:biomimetics9070415.
Reducing resistance to surface friction is challenging in the field of engineering. Natural biological systems have evolved unique functional surfaces or special physiological functions to adapt to their complex environments over centuries. Among these biological wonders, fish, one of the oldest in the vertebrate group, have garnered attention due to their exceptional fluid dynamics capabilities. Fish skin has inspired innovation in reducing surface friction due to its unique structures and material properties. Herein, drawing inspiration from the unique properties of fish scales, a periodic array of fish scales was fabricated by laser ablation on a polished aluminum template. The morphology of the biomimetic fish scale surface was characterized using scanning electron microscopy and a white-light interfering profilometer. Drag reduction performance was measured in a closed circulating water tunnel. The maximum drag reduction was 10.26% at a Reynolds number of 39,532, and the drag reduction performance gradually decreased with an increase in the distance between fish scales. The mechanism of the biomimetic drag reduction surface was analyzed using computational fluid dynamics. Streamwise vortices were generated at the valley of the biomimetic fish scale, replacing sliding friction with rolling friction. These results are expected to provide a foundation for in-depth analysis of the hydrodynamic performance of fish and serve as new inspiration for drag reduction and antifouling.
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@article {pmid39056856,
year = {2024},
author = {Chen, D and Zhang, B and Zhang, H and Shangguan, Z and Sun, C and Cui, X and Liu, X and Zhao, Z and Liu, G and Chen, H},
title = {Laser Ablating Biomimetic Periodic Array Fish Scale Surface for Drag Reduction.},
journal = {Biomimetics (Basel, Switzerland)},
volume = {9},
number = {7},
pages = {},
doi = {10.3390/biomimetics9070415},
pmid = {39056856},
issn = {2313-7673},
support = {52305311, 52205297, 51935001, 51725501, and T2121003//National Natural Science Foundation of China/ ; ZR2023QE018//Shandong Provincial Natural Science Foundation/ ; },
abstract = {Reducing resistance to surface friction is challenging in the field of engineering. Natural biological systems have evolved unique functional surfaces or special physiological functions to adapt to their complex environments over centuries. Among these biological wonders, fish, one of the oldest in the vertebrate group, have garnered attention due to their exceptional fluid dynamics capabilities. Fish skin has inspired innovation in reducing surface friction due to its unique structures and material properties. Herein, drawing inspiration from the unique properties of fish scales, a periodic array of fish scales was fabricated by laser ablation on a polished aluminum template. The morphology of the biomimetic fish scale surface was characterized using scanning electron microscopy and a white-light interfering profilometer. Drag reduction performance was measured in a closed circulating water tunnel. The maximum drag reduction was 10.26% at a Reynolds number of 39,532, and the drag reduction performance gradually decreased with an increase in the distance between fish scales. The mechanism of the biomimetic drag reduction surface was analyzed using computational fluid dynamics. Streamwise vortices were generated at the valley of the biomimetic fish scale, replacing sliding friction with rolling friction. These results are expected to provide a foundation for in-depth analysis of the hydrodynamic performance of fish and serve as new inspiration for drag reduction and antifouling.},
}
RevDate: 2024-07-22
Elasto-inertial instabilities in the merging flow of viscoelastic fluids.
Soft matter [Epub ahead of print].
Many engineering and natural phenomena involve the merging of two fluid streams through a T-junction. Previous studies of such merging flows have been focused primarily upon Newtonian fluids. We observed in our recent experiment with five different polymer solutions a direct change from an undisturbed to either a steady vortical or unsteady three-dimensional flow at the T-junction with increasing inertia. The transition state(s) in between these two types of merging flow patterns is, however, yet to be known. We present here a systematic experimental study of the merging flow of polyethylene oxide (PEO) solutions with varying polymer concentrations and molecular weights. Two new paths of flow development are identified with the increase of Reynolds number: one is the transition in very weakly viscoelastic fluids first to steady vortical flow and then to a juxtaposition state with an unsteady elastic eddy zone in the middle and a steady inertial vortex on each side, and the other is the transition in weakly viscoelastic fluids first to a steady vortical and/or a juxtaposition state and then to a fully unsteady flow. Interestingly, the threshold Reynolds number for the onset of elastic instabilities in the merging flow is not a monotonic function of the elasticity number, but instead follows a power-law dependence on the polymer concentration relative to its overlap value. Such a dependence turns out qualitatively consistent with the prediction of the McKinley-Pakdel criterion.
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@article {pmid39036949,
year = {2024},
author = {Raihan, MK and Kim, N and Song, Y and Xuan, X},
title = {Elasto-inertial instabilities in the merging flow of viscoelastic fluids.},
journal = {Soft matter},
volume = {},
number = {},
pages = {},
doi = {10.1039/d4sm00743c},
pmid = {39036949},
issn = {1744-6848},
abstract = {Many engineering and natural phenomena involve the merging of two fluid streams through a T-junction. Previous studies of such merging flows have been focused primarily upon Newtonian fluids. We observed in our recent experiment with five different polymer solutions a direct change from an undisturbed to either a steady vortical or unsteady three-dimensional flow at the T-junction with increasing inertia. The transition state(s) in between these two types of merging flow patterns is, however, yet to be known. We present here a systematic experimental study of the merging flow of polyethylene oxide (PEO) solutions with varying polymer concentrations and molecular weights. Two new paths of flow development are identified with the increase of Reynolds number: one is the transition in very weakly viscoelastic fluids first to steady vortical flow and then to a juxtaposition state with an unsteady elastic eddy zone in the middle and a steady inertial vortex on each side, and the other is the transition in weakly viscoelastic fluids first to a steady vortical and/or a juxtaposition state and then to a fully unsteady flow. Interestingly, the threshold Reynolds number for the onset of elastic instabilities in the merging flow is not a monotonic function of the elasticity number, but instead follows a power-law dependence on the polymer concentration relative to its overlap value. Such a dependence turns out qualitatively consistent with the prediction of the McKinley-Pakdel criterion.},
}
RevDate: 2024-07-19
Controlled Delivery of H2O2: A Three-Enzyme Cascade Flow Reactor for Peroxidase-Catalyzed Reactions.
ACS sustainable chemistry & engineering, 12(28):10555-10566.
Peroxidases are promising catalysts for oxidation reactions, yet their practical utility has been hindered by the fact that they require hydrogen peroxide (H2O2), which at high concentrations can cause deactivation of enzymes. Practical processes involving the use of peroxidases require the frequent addition of low concentrations of H2O2. In situ generation of H2O2 can be achieved using oxidase-type enzymes. In this study, a three-enzyme cascade system comprised of a H2O2 generator (glucose oxidase (GOx)), H2O2-dependent enzymes (chloroperoxidase (CPO) or horseradish peroxidase (HRP)), and a H2O2 scavenger (catalase (CAT)) was deployed in a flow reactor. Immobilization of the enzymes on a graphite rod was achieved through electrochemically driven physical adsorption, followed by cross-linking with glutaraldehyde. Modeling studies indicated that the flow in the reactor was laminar (Reynolds number, R e < 2000) and was nearly fully developed at the midplane of the annular reactor. Immobilized CAT and GOx displayed good stability, retaining 79% and 84% of their initial activity, respectively, after three cycles of operation. Conversely, immobilized CPO exhibited a considerable reduction in activity after one use, retaining only 30% of its initial activity. The GOx-CAT-GRE system enabled controlled delivery of H2O2 in a more stable manner with a 4-fold enhancement in the oxidation of indole compared to the direct addition of H2O2. Using CPO in solution coupled with GOx-CAT-GRE yields of 90% for the oxidation of indole to 2-oxyindole and of 93% and 91% for the chlorination of thymol and carvacrol, respectively.
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@article {pmid39027729,
year = {2024},
author = {Arshi, S and Madane, K and Shortall, K and Hailo, G and Alvarez-Malmagro, J and Xiao, X and Szymanńska, K and Belochapkine, S and Ranade, VV and Magner, E},
title = {Controlled Delivery of H2O2: A Three-Enzyme Cascade Flow Reactor for Peroxidase-Catalyzed Reactions.},
journal = {ACS sustainable chemistry & engineering},
volume = {12},
number = {28},
pages = {10555-10566},
doi = {10.1021/acssuschemeng.4c03220},
pmid = {39027729},
issn = {2168-0485},
abstract = {Peroxidases are promising catalysts for oxidation reactions, yet their practical utility has been hindered by the fact that they require hydrogen peroxide (H2O2), which at high concentrations can cause deactivation of enzymes. Practical processes involving the use of peroxidases require the frequent addition of low concentrations of H2O2. In situ generation of H2O2 can be achieved using oxidase-type enzymes. In this study, a three-enzyme cascade system comprised of a H2O2 generator (glucose oxidase (GOx)), H2O2-dependent enzymes (chloroperoxidase (CPO) or horseradish peroxidase (HRP)), and a H2O2 scavenger (catalase (CAT)) was deployed in a flow reactor. Immobilization of the enzymes on a graphite rod was achieved through electrochemically driven physical adsorption, followed by cross-linking with glutaraldehyde. Modeling studies indicated that the flow in the reactor was laminar (Reynolds number, R e < 2000) and was nearly fully developed at the midplane of the annular reactor. Immobilized CAT and GOx displayed good stability, retaining 79% and 84% of their initial activity, respectively, after three cycles of operation. Conversely, immobilized CPO exhibited a considerable reduction in activity after one use, retaining only 30% of its initial activity. The GOx-CAT-GRE system enabled controlled delivery of H2O2 in a more stable manner with a 4-fold enhancement in the oxidation of indole compared to the direct addition of H2O2. Using CPO in solution coupled with GOx-CAT-GRE yields of 90% for the oxidation of indole to 2-oxyindole and of 93% and 91% for the chlorination of thymol and carvacrol, respectively.},
}
RevDate: 2024-07-18
Droplet Microfluidic Method for Estimating the Dynamic Interfacial Tension of Ion-Crosslinked Sodium Alginate Microspheres.
Langmuir : the ACS journal of surfaces and colloids [Epub ahead of print].
The research focuses on optimizing the production of hydrogel microspheres using droplet microfluidics for pharmaceutical and bioengineering applications. A semiempirical method has been developed to predict the dynamic interfacial tension at the interface of ion-cross-linked sodium alginate microsphere-sunflower oil modified with glacial acetic acid and Tween 80 surfactant. These microspheres are produced in a small-scale coaxial device that is manufactured using affordable DLP/LCD 3D printing technology with a transparent photopolymer. The method was tested to design the minireactor in the device, which allows for the production of fully cross-linked microspheres that are ready for use at the output of the reactor without additional cross-linking steps in the microsphere collector. The mathematical expression for estimating the interfacial tension at the moment of formation of a hydrogel microsphere includes the Reynolds number for a two-phase liquid, the Ohnesorge number, and the surface tension at the liquid-air interface for continuous medium flow (modified oil). The reliability of the prediction is confirmed for continuous medium and dispersed phase flow rates of 0.8-3.2 and 0.01-0.08 mL/min, respectively. The evolution of the interfacial tension from the moment the microspheres formed and the estimated ultimate interfacial tension in a cross-linked hydrogel-modified oil system contributed to the reliable determination of the linear size of a minireactor. The ultimate interfacial tension of 76.5 ± 0.3 mN/m was determined using the Young-Laplace equation, which is based on measuring the surface free energy of the hydrogel as soft matter using the Owens-Wendt method. Additionally, the equilibrium static contact angle of the fully cross-linked hydrogel surface wetted with oil is measured using the sessile drop method. From a practical perspective, a method for optimizing and streamlining the high-tech manufacturing of cross-linked polymer microspheres and mini- and microchannel devices for use in bioengineering and pharmaceutical applications is suggested.
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@article {pmid39025780,
year = {2024},
author = {Ashikhmin, A and Piskunov, M and Kochkin, D and Ronshin, F and Chen, L},
title = {Droplet Microfluidic Method for Estimating the Dynamic Interfacial Tension of Ion-Crosslinked Sodium Alginate Microspheres.},
journal = {Langmuir : the ACS journal of surfaces and colloids},
volume = {},
number = {},
pages = {},
doi = {10.1021/acs.langmuir.4c01940},
pmid = {39025780},
issn = {1520-5827},
abstract = {The research focuses on optimizing the production of hydrogel microspheres using droplet microfluidics for pharmaceutical and bioengineering applications. A semiempirical method has been developed to predict the dynamic interfacial tension at the interface of ion-cross-linked sodium alginate microsphere-sunflower oil modified with glacial acetic acid and Tween 80 surfactant. These microspheres are produced in a small-scale coaxial device that is manufactured using affordable DLP/LCD 3D printing technology with a transparent photopolymer. The method was tested to design the minireactor in the device, which allows for the production of fully cross-linked microspheres that are ready for use at the output of the reactor without additional cross-linking steps in the microsphere collector. The mathematical expression for estimating the interfacial tension at the moment of formation of a hydrogel microsphere includes the Reynolds number for a two-phase liquid, the Ohnesorge number, and the surface tension at the liquid-air interface for continuous medium flow (modified oil). The reliability of the prediction is confirmed for continuous medium and dispersed phase flow rates of 0.8-3.2 and 0.01-0.08 mL/min, respectively. The evolution of the interfacial tension from the moment the microspheres formed and the estimated ultimate interfacial tension in a cross-linked hydrogel-modified oil system contributed to the reliable determination of the linear size of a minireactor. The ultimate interfacial tension of 76.5 ± 0.3 mN/m was determined using the Young-Laplace equation, which is based on measuring the surface free energy of the hydrogel as soft matter using the Owens-Wendt method. Additionally, the equilibrium static contact angle of the fully cross-linked hydrogel surface wetted with oil is measured using the sessile drop method. From a practical perspective, a method for optimizing and streamlining the high-tech manufacturing of cross-linked polymer microspheres and mini- and microchannel devices for use in bioengineering and pharmaceutical applications is suggested.},
}
RevDate: 2024-07-18
Emergence of order from chaos through a continuous phase transition in a turbulent reactive flow system.
Physical review. E, 109(6-1):064214.
As the Reynolds number is increased, a laminar fluid flow becomes turbulent, and the range of time and length scales associated with the flow increases. Yet, in a turbulent reactive flow system, as we increase the Reynolds number, we observe the emergence of a single dominant timescale in the acoustic pressure fluctuations, as indicated by its loss of multifractality. Such emergence of order from chaos is intriguing. We perform experiments in a turbulent reactive flow system consisting of flame, acoustic, and hydrodynamic subsystems interacting nonlinearly. We study the evolution of short-time correlated dynamics between the acoustic field and the flame in the spatiotemporal domain of the system. The order parameter, defined as the fraction of the correlated dynamics, increases gradually from zero to one. We find that the susceptibility of the order parameter, correlation length, and correlation time diverge at a critical point between chaos and order. Our results show that the observed emergence of order from chaos is a continuous phase transition. Moreover, we provide experimental evidence that the critical exponents characterizing this transition fall in the universality class of directed percolation. Our paper demonstrates how a real-world complex, nonequilibrium turbulent reactive flow system exhibits universal behavior near a critical point.
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@article {pmid39020933,
year = {2024},
author = {Sudarsanan, S and Roy, A and Pavithran, I and Tandon, S and Sujith, RI},
title = {Emergence of order from chaos through a continuous phase transition in a turbulent reactive flow system.},
journal = {Physical review. E},
volume = {109},
number = {6-1},
pages = {064214},
doi = {10.1103/PhysRevE.109.064214},
pmid = {39020933},
issn = {2470-0053},
abstract = {As the Reynolds number is increased, a laminar fluid flow becomes turbulent, and the range of time and length scales associated with the flow increases. Yet, in a turbulent reactive flow system, as we increase the Reynolds number, we observe the emergence of a single dominant timescale in the acoustic pressure fluctuations, as indicated by its loss of multifractality. Such emergence of order from chaos is intriguing. We perform experiments in a turbulent reactive flow system consisting of flame, acoustic, and hydrodynamic subsystems interacting nonlinearly. We study the evolution of short-time correlated dynamics between the acoustic field and the flame in the spatiotemporal domain of the system. The order parameter, defined as the fraction of the correlated dynamics, increases gradually from zero to one. We find that the susceptibility of the order parameter, correlation length, and correlation time diverge at a critical point between chaos and order. Our results show that the observed emergence of order from chaos is a continuous phase transition. Moreover, we provide experimental evidence that the critical exponents characterizing this transition fall in the universality class of directed percolation. Our paper demonstrates how a real-world complex, nonequilibrium turbulent reactive flow system exhibits universal behavior near a critical point.},
}
RevDate: 2024-07-18
Insights on phase speed and the critical Reynolds number of falling films.
Physical review. E, 109(6-2):065103.
We revisit the studies of gravity-driven viscous falling films with and without imposed shear stress to provide new perspectives on phase speed and the critical Reynolds number for surface instability. We use the traditional long-wave expansion technique implemented for investigating the linear stability analysis [C. S. Yih, Phys. Fluids 6, 321 (1963)0031-917110.1063/1.1706737]. The principal purpose is to create a unified relationship between the leading-order phase speed and the critical Reynolds number that will hold for falling films on impermeable substrates with or without shear stress acting at the liquid film surface. The analytical result demonstrates that the critical Reynolds number for the onset of surface instability is [5/(2c_{0})]cotθ, where c_{0} is the leading-order phase speed of the surface mode and θ is the angle of inclination with the horizontal. Clearly, the critical Reynolds number of the surface mode is explicitly dependent on the leading-order phase speed. Furthermore, we reveal that the basic parallel flow with or without imposed shear stress is linearly unstable to infinitesimal disturbances if the modified Reynolds number, Re_{M}=(Rec_{0}/cotθ)[ReistheReynoldsnumber,andθ≠π/2], is greater than its critical value of 5/2, which is independent of the shear stress applied at the film surface. In addition, it is demonstrated that Re_{M} controls the surface instability in the long-wave regime for both shear-imposed and non-shear-imposed film flows.
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@article {pmid39020875,
year = {2024},
author = {Samanta, A},
title = {Insights on phase speed and the critical Reynolds number of falling films.},
journal = {Physical review. E},
volume = {109},
number = {6-2},
pages = {065103},
doi = {10.1103/PhysRevE.109.065103},
pmid = {39020875},
issn = {2470-0053},
abstract = {We revisit the studies of gravity-driven viscous falling films with and without imposed shear stress to provide new perspectives on phase speed and the critical Reynolds number for surface instability. We use the traditional long-wave expansion technique implemented for investigating the linear stability analysis [C. S. Yih, Phys. Fluids 6, 321 (1963)0031-917110.1063/1.1706737]. The principal purpose is to create a unified relationship between the leading-order phase speed and the critical Reynolds number that will hold for falling films on impermeable substrates with or without shear stress acting at the liquid film surface. The analytical result demonstrates that the critical Reynolds number for the onset of surface instability is [5/(2c_{0})
]cotθ, where c_{0}
is the leading-order phase speed of the surface mode and θ is the angle of inclination with the horizontal. Clearly, the critical Reynolds number of the surface mode is explicitly dependent on the leading-order phase speed. Furthermore, we reveal that the basic parallel flow with or without imposed shear stress is linearly unstable to infinitesimal disturbances if the modified Reynolds number, Re_{M}=
(Rec_{0}/
cotθ)[ReistheReynoldsnumber,andθ≠π/2], is greater than its critical value of 5/2, which is independent of the shear stress applied at the film surface. In addition, it is demonstrated that Re_{M}
controls the surface instability in the long-wave regime for both shear-imposed and non-shear-imposed film flows.},
}
RevDate: 2024-07-15
Optimization of passive micromixers: effects of pillar configuration and gaps on mixing efficiency.
Scientific reports, 14(1):16245.
Chemical bioreactions play a significant role in many of the microfluidic devices, and their applications in biomedical science have seen substantial growth. Given that effective mixing is vital for initiating biochemical reactions in many applications, micromixers have become increasingly prevalent for high-throughput assays. In this research, a numerical study using the finite element method was conducted to examine the fluid flow and mass transfer characteristics in novel micromixers featuring an array of pillars. The study utilized two-dimensional geometries. The impact of pillar configuration on mixing performance was evaluated using concentration distribution and mixing index as key metrics. The study explores the effects of pillar array design on mixing performance and pressure drop, drawing from principles such as contraction-expansion and split-recombine. Two configurations of pillar arrays, slanted and arrowhead, are introduced, each undergoing investigation regarding parameters such as pillar diameter, gap size between pillar groups, distance between pillars, and vertical shift in pillar groups. Subsequently, optimal micromixers are identified, exhibiting mixing efficiency exceeding 99.7% at moderate Reynolds number (Re = 1), a level typically challenging for micromixers to attain high mixing efficiency. Notably, the pressure drop remains low at 1102 Pa. Furthermore, the variations in mixing index over time and across different positions along the channel are examined. Both configurations demonstrate short mixing lengths and times. At a distance of 4300 μm from the inlet, the slanted and arrowhead configurations yielded mixing indices of 97.2% and 98.9%, respectively. The micromixers could provide a mixing index of 99.5% at the channel's end within 8 s. Additionally, both configurations exceeded 90% mixing indices by the 3 s. The combination of rapid mixing, low pressure drop, and short mixing length positions the novel micromixers as highly promising for microfluidic applications.
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@article {pmid39009602,
year = {2024},
author = {Kheirkhah Barzoki, A},
title = {Optimization of passive micromixers: effects of pillar configuration and gaps on mixing efficiency.},
journal = {Scientific reports},
volume = {14},
number = {1},
pages = {16245},
pmid = {39009602},
issn = {2045-2322},
abstract = {Chemical bioreactions play a significant role in many of the microfluidic devices, and their applications in biomedical science have seen substantial growth. Given that effective mixing is vital for initiating biochemical reactions in many applications, micromixers have become increasingly prevalent for high-throughput assays. In this research, a numerical study using the finite element method was conducted to examine the fluid flow and mass transfer characteristics in novel micromixers featuring an array of pillars. The study utilized two-dimensional geometries. The impact of pillar configuration on mixing performance was evaluated using concentration distribution and mixing index as key metrics. The study explores the effects of pillar array design on mixing performance and pressure drop, drawing from principles such as contraction-expansion and split-recombine. Two configurations of pillar arrays, slanted and arrowhead, are introduced, each undergoing investigation regarding parameters such as pillar diameter, gap size between pillar groups, distance between pillars, and vertical shift in pillar groups. Subsequently, optimal micromixers are identified, exhibiting mixing efficiency exceeding 99.7% at moderate Reynolds number (Re = 1), a level typically challenging for micromixers to attain high mixing efficiency. Notably, the pressure drop remains low at 1102 Pa. Furthermore, the variations in mixing index over time and across different positions along the channel are examined. Both configurations demonstrate short mixing lengths and times. At a distance of 4300 μm from the inlet, the slanted and arrowhead configurations yielded mixing indices of 97.2% and 98.9%, respectively. The micromixers could provide a mixing index of 99.5% at the channel's end within 8 s. Additionally, both configurations exceeded 90% mixing indices by the 3 s. The combination of rapid mixing, low pressure drop, and short mixing length positions the novel micromixers as highly promising for microfluidic applications.},
}
RevDate: 2024-07-12
Experimental investigation of multi-step airfoils in low Reynolds numbers applications.
Heliyon, 10(12):e32919 pii:S2405-8440(24)08950-3.
This study provides a detailed analysis of the aerodynamic performance of various airfoil configurations, focusing on lift coefficient, stall characteristics, and maximum lift-to-drag ratio. The investigation includes the NACA23012C profile and configurations with different step geometries, ranging from one-step to five-step designs. Experimental measurements were conducted using a well-equipped aerodynamic laboratory, Institute of Aviation Engineering and Technology (IAET), Giza, Egypt. The lab features a wind tunnel, propeller test rig, and data acquisition system. The experiments were conducted meticulously to ensure accuracy and reproducibility, with a standardized method employed for uncertainty analysis. The results reveal distinct aerodynamic behaviors among the different configurations, highlighting the significant impact of design variations on aerodynamic performance. Notably, the three-step configuration consistently exhibited high performance, with a competitive or superior lift coefficient across a range of Reynolds numbers, showing an improvement of up to 35.1 %. Similarly, the four-step configuration demonstrated substantial increases in lift-to-drag ratios, reaching up to 53.2 %, while the five-step configuration exhibited varying trends with a minimum drag coefficient. The study also investigated stall characteristics and sensitivity to Reynolds numbers, revealing the complex trade-offs inherent in airfoil design. The findings provide valuable insights into optimizing airfoil performance under different operational conditions. Additionally, the adoption of two and three stepped airfoils resulted in significant reductions in blade material and associated costs for turbine blades.
Additional Links: PMID-38994047
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@article {pmid38994047,
year = {2024},
author = {Aziz, MA and Gaheen, OA and Benini, E and Elsayed, AM},
title = {Experimental investigation of multi-step airfoils in low Reynolds numbers applications.},
journal = {Heliyon},
volume = {10},
number = {12},
pages = {e32919},
doi = {10.1016/j.heliyon.2024.e32919},
pmid = {38994047},
issn = {2405-8440},
abstract = {This study provides a detailed analysis of the aerodynamic performance of various airfoil configurations, focusing on lift coefficient, stall characteristics, and maximum lift-to-drag ratio. The investigation includes the NACA23012C profile and configurations with different step geometries, ranging from one-step to five-step designs. Experimental measurements were conducted using a well-equipped aerodynamic laboratory, Institute of Aviation Engineering and Technology (IAET), Giza, Egypt. The lab features a wind tunnel, propeller test rig, and data acquisition system. The experiments were conducted meticulously to ensure accuracy and reproducibility, with a standardized method employed for uncertainty analysis. The results reveal distinct aerodynamic behaviors among the different configurations, highlighting the significant impact of design variations on aerodynamic performance. Notably, the three-step configuration consistently exhibited high performance, with a competitive or superior lift coefficient across a range of Reynolds numbers, showing an improvement of up to 35.1 %. Similarly, the four-step configuration demonstrated substantial increases in lift-to-drag ratios, reaching up to 53.2 %, while the five-step configuration exhibited varying trends with a minimum drag coefficient. The study also investigated stall characteristics and sensitivity to Reynolds numbers, revealing the complex trade-offs inherent in airfoil design. The findings provide valuable insights into optimizing airfoil performance under different operational conditions. Additionally, the adoption of two and three stepped airfoils resulted in significant reductions in blade material and associated costs for turbine blades.},
}
RevDate: 2024-07-11
Turbulent blood flow in a cerebral artery with an aneurysm.
Journal of biomechanics, 172:112214 pii:S0021-9290(24)00292-6 [Epub ahead of print].
Unruptured intracranial aneurysms are common in the general population, and many uncertainties remain when predicting rupture risks and treatment outcomes. One of the cutting-edge tools used to investigate this condition is computational fluid dynamics (CFD). However, CFD is not yet mature enough to guide the clinical management of this disease. In addition, recent studies have reported significant flow instabilities when refined numerical methods are used. Questions remain as to how to properly simulate and evaluate this flow, and whether these instabilities are really turbulence. The purpose of the present study is to evaluate the impact of the simulation setup on the results and investigate the occurrence of turbulence in a cerebral artery with an aneurysm. For this purpose, direct numerical simulations were performed with up to 200 cardiac cycles and with data sampling rates of up to 100,000 times per cardiac cycle. Through phase-averaging or triple decomposition, the contributions of turbulence and of laminar pulsatile waves to the velocity, pressure and wall shear stress fluctuations were distinguished. For example, the commonly used oscillatory shear index was found to be closely related to the laminar waves introduced at the inlet, rather than turbulence. The turbulence energy cascade was evaluated through energy spectrum estimates, revealing that, despite the low flow rates and Reynolds number, the flow is turbulent near the aneurysm. Phase-averaging was shown to be an approach that can help researchers better understand this flow, although the results are highly dependent on simulation setup and post-processing choices.
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@article {pmid38991421,
year = {2024},
author = {Luciano, RD and da Silva, BL and Chen, XB and Bergstrom, DJ},
title = {Turbulent blood flow in a cerebral artery with an aneurysm.},
journal = {Journal of biomechanics},
volume = {172},
number = {},
pages = {112214},
doi = {10.1016/j.jbiomech.2024.112214},
pmid = {38991421},
issn = {1873-2380},
abstract = {Unruptured intracranial aneurysms are common in the general population, and many uncertainties remain when predicting rupture risks and treatment outcomes. One of the cutting-edge tools used to investigate this condition is computational fluid dynamics (CFD). However, CFD is not yet mature enough to guide the clinical management of this disease. In addition, recent studies have reported significant flow instabilities when refined numerical methods are used. Questions remain as to how to properly simulate and evaluate this flow, and whether these instabilities are really turbulence. The purpose of the present study is to evaluate the impact of the simulation setup on the results and investigate the occurrence of turbulence in a cerebral artery with an aneurysm. For this purpose, direct numerical simulations were performed with up to 200 cardiac cycles and with data sampling rates of up to 100,000 times per cardiac cycle. Through phase-averaging or triple decomposition, the contributions of turbulence and of laminar pulsatile waves to the velocity, pressure and wall shear stress fluctuations were distinguished. For example, the commonly used oscillatory shear index was found to be closely related to the laminar waves introduced at the inlet, rather than turbulence. The turbulence energy cascade was evaluated through energy spectrum estimates, revealing that, despite the low flow rates and Reynolds number, the flow is turbulent near the aneurysm. Phase-averaging was shown to be an approach that can help researchers better understand this flow, although the results are highly dependent on simulation setup and post-processing choices.},
}
RevDate: 2024-07-10
Effects of turbulence on diatoms of the genus pseudo-nitzschia spp. And associated bacteria.
FEMS microbiology ecology pii:7710742 [Epub ahead of print].
Turbulence is one of the least investigated environmental factors impacting the ecophysiology of phytoplankton, both at the community and individual species level. Here, we investigated, for the first time, the effect of a turbulence gradient (${\rm{Reynolds\ number}}$, from ${\rm{R}}{{\rm{e}}}_{\rm{\lambda }} = 0$ to ${\rm{R}}{{\rm{e}}}_{\rm{\lambda }} = 360$) on two species of the marine diatom Pseudo-nitzschia and their associated bacterial communities under laboratory conditions. Cell abundance, domoic acid (DA) production, chain formation, and Chl a content of P. fraudulenta and P. multiseries were higher for intermediate turbulence (${\rm{R}}{{\rm{e}}}_{\rm{\lambda }} = 160$ or $240$). DA was detectable only in P. multiseries samples. These observations were supported by transcriptomic analyses results which suggested the turbulence related induction of the expression of the DA production locus, with a linkage to an increased photosynthetic activity of the total metatranscriptome. This study also highlighted a higher richness of the bacterial community associated with the non-toxic strain of P. fraudulenta in comparison to the toxic strain of P. multiseries. Bacillus was an important genus in P. multiseries cultures (relative abundance 15.5%) and its highest abundances coincided with the highest DA levels. However, associated bacterial communities of both Pseudo-nitzschia species did not show clear patterns relative to turbulence intensity.
Additional Links: PMID-38986513
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@article {pmid38986513,
year = {2024},
author = {Maire, Y and Schmitt, FG and Kormas, K and Vasileiadis, S and Caruana, A and Skouroliakou, DI and Bampouris, V and Courcot, L and Hervé, F and Crouvoisier, M and Christaki, U},
title = {Effects of turbulence on diatoms of the genus pseudo-nitzschia spp. And associated bacteria.},
journal = {FEMS microbiology ecology},
volume = {},
number = {},
pages = {},
doi = {10.1093/femsec/fiae094},
pmid = {38986513},
issn = {1574-6941},
abstract = {Turbulence is one of the least investigated environmental factors impacting the ecophysiology of phytoplankton, both at the community and individual species level. Here, we investigated, for the first time, the effect of a turbulence gradient (${\rm{Reynolds\ number}}
$, from ${\rm{R}}
{{\rm{e}}
}_
{\rm{\lambda }}
= 0$ to ${\rm{R}}
{{\rm{e}}
}_
{\rm{\lambda }}
= 360$) on two species of the marine diatom Pseudo-nitzschia and their associated bacterial communities under laboratory conditions. Cell abundance, domoic acid (DA) production, chain formation, and Chl a content of P. fraudulenta and P. multiseries were higher for intermediate turbulence (${\rm{R}}
{{\rm{e}}
}_
{\rm{\lambda }}
= 160$ or $240$). DA was detectable only in P. multiseries samples. These observations were supported by transcriptomic analyses results which suggested the turbulence related induction of the expression of the DA production locus, with a linkage to an increased photosynthetic activity of the total metatranscriptome. This study also highlighted a higher richness of the bacterial community associated with the non-toxic strain of P. fraudulenta in comparison to the toxic strain of P. multiseries. Bacillus was an important genus in P. multiseries cultures (relative abundance 15.5%) and its highest abundances coincided with the highest DA levels. However, associated bacterial communities of both Pseudo-nitzschia species did not show clear patterns relative to turbulence intensity.},
}
RevDate: 2024-07-10
Controlling hypersonic boundary layer transition with localized cooling and metasurface treatments.
Scientific reports, 14(1):15928.
This study investigates a novel method to control hypersonic boundary layer transition using a combined local cooling and local metasurface treatment. The method's effectiveness was investigated on a 5-degree half-angle blunt wedge with a nose radius of 0.0254 mm at a freestream Mach number of 6.0 using direct numerical simulations and linear stability theory. We explored four cases: (i) adiabatic baseline case, (ii) locally cooled case, (iii) local metasurface case, and (iv) combined local cooling-local metasurface case. Results showed that the combined local cooling-local metasurface treatment significantly reduced both wall pressure disturbance amplitude and the density perturbation amplitude around the sonic line, indicating a potential for controlling hypersonic boundary layer transition. In the local cooling-local metasurface case, the disturbance amplitude at the end of the computational domain was 270 times lower than the baseline case. The study also examined the impact of Reynolds numbers, ranging from 25.59 million per meter to 32.80 million per meter. Unsteady simulations revealed that the Reynolds number had a negligible effect on the local cooling-local metasurface performance, indicating that the proposed method applies to a wide range of flight conditions.
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@article {pmid38987632,
year = {2024},
author = {Oz, F and Kara, K},
title = {Controlling hypersonic boundary layer transition with localized cooling and metasurface treatments.},
journal = {Scientific reports},
volume = {14},
number = {1},
pages = {15928},
pmid = {38987632},
issn = {2045-2322},
support = {OAC-1531128//National Science Foundation/ ; },
abstract = {This study investigates a novel method to control hypersonic boundary layer transition using a combined local cooling and local metasurface treatment. The method's effectiveness was investigated on a 5-degree half-angle blunt wedge with a nose radius of 0.0254 mm at a freestream Mach number of 6.0 using direct numerical simulations and linear stability theory. We explored four cases: (i) adiabatic baseline case, (ii) locally cooled case, (iii) local metasurface case, and (iv) combined local cooling-local metasurface case. Results showed that the combined local cooling-local metasurface treatment significantly reduced both wall pressure disturbance amplitude and the density perturbation amplitude around the sonic line, indicating a potential for controlling hypersonic boundary layer transition. In the local cooling-local metasurface case, the disturbance amplitude at the end of the computational domain was 270 times lower than the baseline case. The study also examined the impact of Reynolds numbers, ranging from 25.59 million per meter to 32.80 million per meter. Unsteady simulations revealed that the Reynolds number had a negligible effect on the local cooling-local metasurface performance, indicating that the proposed method applies to a wide range of flight conditions.},
}
RevDate: 2024-07-08
Heat transfer and flow characteristics of a plate-fin heat sink equipped with copper foam and twisted tapes.
Heliyon, 10(12):e32307 pii:S2405-8440(24)08338-5.
The objective of this paper is to present new heat transfer enhancement approaches in plate-fin heat sinks (PFHS) using copper foam and twisted tapes. The motivation behind these concepts is to reduce pressure drop while enhancing heat transfer compared to PFHSs fully inserted with copper foam. The impact of twisted tape type, twist ratio, and Reynolds number (Re) on the heat and flow behaviors inside the PFHS equipped with copper foam (PFHSCF) is investigated. Copper foam has a porosity of 0.932 and a pore density of 40 pores per inch. Stationary and rotating twisted tapes with twist ratios between 2.7 and 4 are tested at Re between 3000 and 6000. The experimental results indicated that the pressure drop of the airflow inside a PFHS equipped with copper foam and a stationary twisted tape (PFHSCF_STT) as well as a PFHS equipped with copper foam and rotating twisted tapes (PFHSCF_RTT) decreased by an average of 34.8 % and 37.9 %, respectively, compared to a PFHSCF. When the twist ratio is decreased from 4 to 2.7, the thermal resistances of PFHSCF_STT and PFHSCF_RTT are reduced by 14.2 and 14.8 %, respectively. Based on assessment, the thermal-hydraulic performance of a PFHSCF_RTT with twist ratios of 2.7 and 3.3 is higher than that of a PFHSCF. To facilitate practical applications, correlations are proposed to predict the Nusselt number and friction factor. Additionally, considering the outcomes of the current study, conducting numerical investigations on the thermal performance of PFHS under different pore densities of copper foam and wider twist ratios of twisted tapes is recommended to determine optimal working conditions for future research.
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@article {pmid38975123,
year = {2024},
author = {Nilpueng, K and Kaseethong, P and Wongwises, S},
title = {Heat transfer and flow characteristics of a plate-fin heat sink equipped with copper foam and twisted tapes.},
journal = {Heliyon},
volume = {10},
number = {12},
pages = {e32307},
doi = {10.1016/j.heliyon.2024.e32307},
pmid = {38975123},
issn = {2405-8440},
abstract = {The objective of this paper is to present new heat transfer enhancement approaches in plate-fin heat sinks (PFHS) using copper foam and twisted tapes. The motivation behind these concepts is to reduce pressure drop while enhancing heat transfer compared to PFHSs fully inserted with copper foam. The impact of twisted tape type, twist ratio, and Reynolds number (Re) on the heat and flow behaviors inside the PFHS equipped with copper foam (PFHSCF) is investigated. Copper foam has a porosity of 0.932 and a pore density of 40 pores per inch. Stationary and rotating twisted tapes with twist ratios between 2.7 and 4 are tested at Re between 3000 and 6000. The experimental results indicated that the pressure drop of the airflow inside a PFHS equipped with copper foam and a stationary twisted tape (PFHSCF_STT) as well as a PFHS equipped with copper foam and rotating twisted tapes (PFHSCF_RTT) decreased by an average of 34.8 % and 37.9 %, respectively, compared to a PFHSCF. When the twist ratio is decreased from 4 to 2.7, the thermal resistances of PFHSCF_STT and PFHSCF_RTT are reduced by 14.2 and 14.8 %, respectively. Based on assessment, the thermal-hydraulic performance of a PFHSCF_RTT with twist ratios of 2.7 and 3.3 is higher than that of a PFHSCF. To facilitate practical applications, correlations are proposed to predict the Nusselt number and friction factor. Additionally, considering the outcomes of the current study, conducting numerical investigations on the thermal performance of PFHS under different pore densities of copper foam and wider twist ratios of twisted tapes is recommended to determine optimal working conditions for future research.},
}
RevDate: 2024-07-06
Flow dynamics and turbulent coherent structures around sediment reduction plates of a sewer system.
Journal of environmental management, 366:121594 pii:S0301-4797(24)01580-9 [Epub ahead of print].
In the management of urban drainage networks, great interest has been generated in the removal of sediments from sewer systems. The unsteady three-dimensional (3D) flow and turbulent coherent structures surrounding sediment reduction plates in a sewer system are investigated by means of the detached-eddy simulation (DES). Particular emphasis is given to detailing the instantaneous velocity and vorticity fields within the grooves, along with an examination of the three-dimensional, long-term, average flow structure at a Reynolds number of approximately 10[5]. Velocity vectors demonstrate continuous flapping of the flow on the groove wall, periodically interacting with ejections of positive and negative vorticity originating from the grooves. The interaction between the three-dimensional groove flow and the shear flow leads to the downstream transport of patches of positive and negative vorticity, which significantly influence sediment transport. The high-velocity shear flows and strong vortices generated in undulating topography, as identified by the Q-criteria, are the key factors contributing to the efficient sediment reduction capabilities of the sediment reduction plates. The sediment reduction plates with partially enclosed structures exhibit low sedimentation rates in grooves on the plate, a broader acceleration region, and a lesser impact on the flow capacity. The results improve the understanding of the hydrodynamics and turbulent coherent structures surrounding the sediment reduction plates while elucidating the driving factors behind the enhancement of sediment scouring and suspension capacities. These results indicate that the redesign of the plates as partially enclosed structures contributes to further improving their sediment reduction performance.
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@article {pmid38971061,
year = {2024},
author = {Li, Z and Wang, B and Wang, F and Sun, B and Li, L},
title = {Flow dynamics and turbulent coherent structures around sediment reduction plates of a sewer system.},
journal = {Journal of environmental management},
volume = {366},
number = {},
pages = {121594},
doi = {10.1016/j.jenvman.2024.121594},
pmid = {38971061},
issn = {1095-8630},
abstract = {In the management of urban drainage networks, great interest has been generated in the removal of sediments from sewer systems. The unsteady three-dimensional (3D) flow and turbulent coherent structures surrounding sediment reduction plates in a sewer system are investigated by means of the detached-eddy simulation (DES). Particular emphasis is given to detailing the instantaneous velocity and vorticity fields within the grooves, along with an examination of the three-dimensional, long-term, average flow structure at a Reynolds number of approximately 10[5]. Velocity vectors demonstrate continuous flapping of the flow on the groove wall, periodically interacting with ejections of positive and negative vorticity originating from the grooves. The interaction between the three-dimensional groove flow and the shear flow leads to the downstream transport of patches of positive and negative vorticity, which significantly influence sediment transport. The high-velocity shear flows and strong vortices generated in undulating topography, as identified by the Q-criteria, are the key factors contributing to the efficient sediment reduction capabilities of the sediment reduction plates. The sediment reduction plates with partially enclosed structures exhibit low sedimentation rates in grooves on the plate, a broader acceleration region, and a lesser impact on the flow capacity. The results improve the understanding of the hydrodynamics and turbulent coherent structures surrounding the sediment reduction plates while elucidating the driving factors behind the enhancement of sediment scouring and suspension capacities. These results indicate that the redesign of the plates as partially enclosed structures contributes to further improving their sediment reduction performance.},
}
RevDate: 2024-07-05
Fluid inertia controls mineral precipitation and clogging in pore to network-scale flows.
Proceedings of the National Academy of Sciences of the United States of America, 121(28):e2401318121.
Mineral precipitation caused by fluid mixing presents complex control and predictability challenges in a variety of natural and engineering processes, including carbon mineralization, geothermal energy, and microfluidics. Precipitation dynamics, particularly under the influence of fluid flow, remain poorly understood. Combining microfluidic experiments and three-dimensional reactive transport simulations, we demonstrate that fluid inertia controls mineral precipitation and clogging at flow intersections, even in laminar flows. We observe distinct precipitation regimes as a function of Reynolds number (Re). At low Reynolds numbers (Re < 10), precipitates form a thin, dense layer along the mixing interface, which shuts precipitation off, while at high Reynolds numbers (Re > 50), strong three-dimensional flows significantly enhance precipitation over the entire intersection, resulting in rapid clogging. When injection rates from two inlets are uneven, flow symmetry-breaking leads to unexpected flow bifurcation phenomena, which result in enhanced concurrent precipitation in both downstream channels. Finally, we extend our findings to rough channel networks and demonstrate that the identified inertial effects on precipitation at the intersection scale are also present and even more dramatic at the network scale. This study sheds light on the fundamental mechanisms underlying mixing-induced mineral precipitation and provides a framework for designing and optimizing processes involving mineral precipitation.
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@article {pmid38968103,
year = {2024},
author = {Yang, W and Chen, MA and Lee, SH and Kang, PK},
title = {Fluid inertia controls mineral precipitation and clogging in pore to network-scale flows.},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
volume = {121},
number = {28},
pages = {e2401318121},
doi = {10.1073/pnas.2401318121},
pmid = {38968103},
issn = {1091-6490},
support = {DE-SC0023429//U.S. Department of Energy (DOE)/ ; ECCS-2025124//National Science Foundation (NSF)/ ; },
abstract = {Mineral precipitation caused by fluid mixing presents complex control and predictability challenges in a variety of natural and engineering processes, including carbon mineralization, geothermal energy, and microfluidics. Precipitation dynamics, particularly under the influence of fluid flow, remain poorly understood. Combining microfluidic experiments and three-dimensional reactive transport simulations, we demonstrate that fluid inertia controls mineral precipitation and clogging at flow intersections, even in laminar flows. We observe distinct precipitation regimes as a function of Reynolds number (Re). At low Reynolds numbers (Re < 10), precipitates form a thin, dense layer along the mixing interface, which shuts precipitation off, while at high Reynolds numbers (Re > 50), strong three-dimensional flows significantly enhance precipitation over the entire intersection, resulting in rapid clogging. When injection rates from two inlets are uneven, flow symmetry-breaking leads to unexpected flow bifurcation phenomena, which result in enhanced concurrent precipitation in both downstream channels. Finally, we extend our findings to rough channel networks and demonstrate that the identified inertial effects on precipitation at the intersection scale are also present and even more dramatic at the network scale. This study sheds light on the fundamental mechanisms underlying mixing-induced mineral precipitation and provides a framework for designing and optimizing processes involving mineral precipitation.},
}
RevDate: 2024-07-03
Stabilization of CsPbBr3 Nanowires Through SU-8 Encapsulation for the Fabrication of Bilayer Microswimmers with Magnetic and Fluorescence Properties.
Small (Weinheim an der Bergstrasse, Germany) [Epub ahead of print].
All-inorganic cesium lead halide (CsPbX3, X = Cl, Br, I) perovskite nanocrystals have drawn great interest because of their excellent photophysical properties and potential applications. However, their poor stability in water greatly limited their use in applications that require stable structures. In this work, a facile approach to stabilize CsPbBr3 nanowires is developed by using SU-8 as a protection medium; thereby creating stable CsPbBr3/SU-8 microstructures. Through photolithography and layer-by-layer deposition, CsPbBr3/SU-8 is used to fabricate bilayer achiral microswimmers (BAMs), which consist of a top CsPbBr3/SU-8 layer and a bottom Fe3O4 magnetic layer. Compared to pure CsPbBr3 nanowires, the CsPbBr3/SU-8 shows long-term structural and fluorescence stability in water against ultrasonication treatment. Due to the magnetic layer, the motion of the microswimmers can be controlled precisely under a rotating magnetic field, allowing them to swim at low Reynolds number and tumble or roll on surfaces. Furthermore, CsPbBr3/SU-8 can be used to fabricate various types of planar microstructures with high throughput, high consistency, and fluorescence properties. This work provides a method for the stabilization of CsPbBr3 and demonstrates the potential to mass fabricate planar microstructures with various shapes, which can be used in different applications such as microrobotics.
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@article {pmid38958090,
year = {2024},
author = {Wang, H and Xiong, J and Cai, Y and Fu, W and Zhong, Y and Jiang, T and Cheang, UK},
title = {Stabilization of CsPbBr3 Nanowires Through SU-8 Encapsulation for the Fabrication of Bilayer Microswimmers with Magnetic and Fluorescence Properties.},
journal = {Small (Weinheim an der Bergstrasse, Germany)},
volume = {},
number = {},
pages = {e2400346},
doi = {10.1002/smll.202400346},
pmid = {38958090},
issn = {1613-6829},
support = {52375569//National Natural Science Foundation of China/ ; RCYX20210609103644015//Science and Technology Innovation Committee Foundation of Shenzhen/ ; 2021ZDZX2037//Department of Education of Guangdong/ ; 2021A1515110212//Guangdong Basic and Applied Basic Research Foundation/ ; 2023A1515012229//Guangdong Basic and Applied Basic Research Foundation/ ; },
abstract = {All-inorganic cesium lead halide (CsPbX3, X = Cl, Br, I) perovskite nanocrystals have drawn great interest because of their excellent photophysical properties and potential applications. However, their poor stability in water greatly limited their use in applications that require stable structures. In this work, a facile approach to stabilize CsPbBr3 nanowires is developed by using SU-8 as a protection medium; thereby creating stable CsPbBr3/SU-8 microstructures. Through photolithography and layer-by-layer deposition, CsPbBr3/SU-8 is used to fabricate bilayer achiral microswimmers (BAMs), which consist of a top CsPbBr3/SU-8 layer and a bottom Fe3O4 magnetic layer. Compared to pure CsPbBr3 nanowires, the CsPbBr3/SU-8 shows long-term structural and fluorescence stability in water against ultrasonication treatment. Due to the magnetic layer, the motion of the microswimmers can be controlled precisely under a rotating magnetic field, allowing them to swim at low Reynolds number and tumble or roll on surfaces. Furthermore, CsPbBr3/SU-8 can be used to fabricate various types of planar microstructures with high throughput, high consistency, and fluorescence properties. This work provides a method for the stabilization of CsPbBr3 and demonstrates the potential to mass fabricate planar microstructures with various shapes, which can be used in different applications such as microrobotics.},
}
RevDate: 2024-07-01
Laboratory investigations of wave-induced transport of plastic debris over a rippled bottom.
The Science of the total environment pii:S0048-9697(24)04528-5 [Epub ahead of print].
Laboratory experiments are conducted in a wave flume to investigate the effect of water waves on the transport of plastic pellets over a rippled bottom. The horizontal velocities of plastic debris are analyzed over the rippled bottom for different wave conditions and plastic elements with different properties. Laboratory investigations determined the characteristic transport patterns of wave-induced plastic debris with a density of ~2.0g/cm3 moving along the rippled bottom. In the first, swing-type motion, the grains move only in the ripple trough with velocities lower than 0.10 m/s. For sliding-type movement, the grains move along the entire rippled surface with velocities in the range of 0.10-0.13 m/s. For higher velocities in the range of 0.15-0.20 m/s, a saltation-type motion becomes dominant. The results show that plastic grains may move up to 2-3 cm above the ripple crest depending on hydrodynamic conditions. The analysis shows that for velocity-skewed flows, sliding-type motion and onshore transport dominate. For acceleration-skewed flows, saltation-type motion and offshore transport dominate, which is attributed to higher boundary layer thickness and phase lag effects. The analysis of the relationship between the particle Reynolds number and the thickness of the turbulent boundary layer reveals that for values of Rep≥1000 and a boundary layer thickness mm saltation-type motion becomes dominant. The direction of transport is affected not only by the density of the sediment and the wave skewness coefficients but also by the dimensions of the bottom ripples. The laboratory investigations also provide insight into the hydrodynamic conditions affecting the transport of plastic debris along the bottom covered with ripples in oscillating nonlinear water flows.
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@article {pmid38950632,
year = {2024},
author = {Stachurska, B and Sulisz, W},
title = {Laboratory investigations of wave-induced transport of plastic debris over a rippled bottom.},
journal = {The Science of the total environment},
volume = {},
number = {},
pages = {174380},
doi = {10.1016/j.scitotenv.2024.174380},
pmid = {38950632},
issn = {1879-1026},
abstract = {Laboratory experiments are conducted in a wave flume to investigate the effect of water waves on the transport of plastic pellets over a rippled bottom. The horizontal velocities of plastic debris are analyzed over the rippled bottom for different wave conditions and plastic elements with different properties. Laboratory investigations determined the characteristic transport patterns of wave-induced plastic debris with a density of ~2.0g/cm3 moving along the rippled bottom. In the first, swing-type motion, the grains move only in the ripple trough with velocities lower than 0.10 m/s. For sliding-type movement, the grains move along the entire rippled surface with velocities in the range of 0.10-0.13 m/s. For higher velocities in the range of 0.15-0.20 m/s, a saltation-type motion becomes dominant. The results show that plastic grains may move up to 2-3 cm above the ripple crest depending on hydrodynamic conditions. The analysis shows that for velocity-skewed flows, sliding-type motion and onshore transport dominate. For acceleration-skewed flows, saltation-type motion and offshore transport dominate, which is attributed to higher boundary layer thickness and phase lag effects. The analysis of the relationship between the particle Reynolds number and the thickness of the turbulent boundary layer reveals that for values of Rep≥1000 and a boundary layer thickness mm saltation-type motion becomes dominant. The direction of transport is affected not only by the density of the sediment and the wave skewness coefficients but also by the dimensions of the bottom ripples. The laboratory investigations also provide insight into the hydrodynamic conditions affecting the transport of plastic debris along the bottom covered with ripples in oscillating nonlinear water flows.},
}
RevDate: 2024-07-01
Acclimatize experimental approach to adjudicate hydraulic coefficients under different bed material configurations and slopes with and without weir.
Heliyon, 10(11):e32162.
The primary purpose of this study was to evaluate the hydraulic coefficient of coarse aggregate grain size beds and hydraulic parameters under random and perpendicular bed configurations, as well as to explore the discharge coefficient for rectangular weirs. The research objectives were to compare flow resistance coefficients, evaluate the discharge coefficient for rectangular weirs, investigate the relationship between roughness coefficient and hydraulic parameters, and validate the theoretical hydraulic equation for the rectangular weir. This was achieved by analysing different bed configurations, bed slopes, and 20 and 30-mm bed materials. Sieve analysis was conducted on bed materials using American-standard sieves to determine their particle size distribution. The experiment was performed in a rectangular flume measuring 12 m in length, 0.31 m in width, and 0.45 m in depth. In a laboratory experiment, water was pumped into a flume using centrifugal pumps, and a rectangular weir was attached downstream for discharge measurement. The experiment investigated factors such as Manning roughness coefficient, bed material geometry, bed slope, and weir shapes. Approximately 1680 tests were conducted to analysed the impact of these factors on discharge and the coefficient of discharge. The average Manning's roughness coefficients for a grain size of 20 mm were 0.019 (with weir) and 0.019 (without weir) in a random bed configuration, and 0.028 (with weir) and 0.027 (without weir) in a perpendicular flow bed configuration. For a grain size of 30 mm, the coefficients were 0.023 (with weir) and 0.022 (without weir) in a random bed configuration, and 0.033 (with weir) and 0.026 (without weir) in a perpendicular flow bed configuration. The presence of a weir has affected Manning's roughness coefficients and discharge coefficients. With a weir, the roughness coefficients have generally been higher compared to without a weir, indicating increased roughness in the channel. The discharge coefficient for a rectangular weir with a grain size of 20 mm ranged from 0.39 to 0.84 (random bed) and 0.27 to 0.68 (perpendicular flow bed), while for a grain size of 30 mm it ranged from 0.31 to 0.81 (random bed) and 0.23 to 0.48 (perpendicular flow bed). The discharge coefficients have varied depending on the grain size and bed configuration, reflecting different flow efficiencies over the weir. Rough particles influenced flow and Manning's roughness coefficient value, then reduced discharge and velocity values. Under two bed configurations and slopes, beds with a grain size of 30 mm have higher roughness coefficients compared to those with a grain size of 20 mm. The models have shown that the roughness coefficient is inversely proportional to the discharge and directly proportional to the tailgate water levels. The coefficient of roughness and discharge coefficient are mainly influenced by the channel slopes, bed roughness, bed grain size, and bed configuration. A randomly configured bed with a 20 mm grain size gravel bed is preferred over a perpendicular bed configuration to handle high discharges. Using a 20 mm grain-size gravel bed in open-channel flow is more suitable than a 30 mm grain-size bed. Relying on the constant friction factor, Manning's n, is not recommended as it may result in design errors. These findings have the potential to improve hydraulic engineering design practices, enhancing the accuracy and efficiency of open-channel flow systems.
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@article {pmid38947461,
year = {2024},
author = {Amsie, AB and Ayalew, AT and Mada, ZM and Finsa, MM},
title = {Acclimatize experimental approach to adjudicate hydraulic coefficients under different bed material configurations and slopes with and without weir.},
journal = {Heliyon},
volume = {10},
number = {11},
pages = {e32162},
pmid = {38947461},
issn = {2405-8440},
abstract = {The primary purpose of this study was to evaluate the hydraulic coefficient of coarse aggregate grain size beds and hydraulic parameters under random and perpendicular bed configurations, as well as to explore the discharge coefficient for rectangular weirs. The research objectives were to compare flow resistance coefficients, evaluate the discharge coefficient for rectangular weirs, investigate the relationship between roughness coefficient and hydraulic parameters, and validate the theoretical hydraulic equation for the rectangular weir. This was achieved by analysing different bed configurations, bed slopes, and 20 and 30-mm bed materials. Sieve analysis was conducted on bed materials using American-standard sieves to determine their particle size distribution. The experiment was performed in a rectangular flume measuring 12 m in length, 0.31 m in width, and 0.45 m in depth. In a laboratory experiment, water was pumped into a flume using centrifugal pumps, and a rectangular weir was attached downstream for discharge measurement. The experiment investigated factors such as Manning roughness coefficient, bed material geometry, bed slope, and weir shapes. Approximately 1680 tests were conducted to analysed the impact of these factors on discharge and the coefficient of discharge. The average Manning's roughness coefficients for a grain size of 20 mm were 0.019 (with weir) and 0.019 (without weir) in a random bed configuration, and 0.028 (with weir) and 0.027 (without weir) in a perpendicular flow bed configuration. For a grain size of 30 mm, the coefficients were 0.023 (with weir) and 0.022 (without weir) in a random bed configuration, and 0.033 (with weir) and 0.026 (without weir) in a perpendicular flow bed configuration. The presence of a weir has affected Manning's roughness coefficients and discharge coefficients. With a weir, the roughness coefficients have generally been higher compared to without a weir, indicating increased roughness in the channel. The discharge coefficient for a rectangular weir with a grain size of 20 mm ranged from 0.39 to 0.84 (random bed) and 0.27 to 0.68 (perpendicular flow bed), while for a grain size of 30 mm it ranged from 0.31 to 0.81 (random bed) and 0.23 to 0.48 (perpendicular flow bed). The discharge coefficients have varied depending on the grain size and bed configuration, reflecting different flow efficiencies over the weir. Rough particles influenced flow and Manning's roughness coefficient value, then reduced discharge and velocity values. Under two bed configurations and slopes, beds with a grain size of 30 mm have higher roughness coefficients compared to those with a grain size of 20 mm. The models have shown that the roughness coefficient is inversely proportional to the discharge and directly proportional to the tailgate water levels. The coefficient of roughness and discharge coefficient are mainly influenced by the channel slopes, bed roughness, bed grain size, and bed configuration. A randomly configured bed with a 20 mm grain size gravel bed is preferred over a perpendicular bed configuration to handle high discharges. Using a 20 mm grain-size gravel bed in open-channel flow is more suitable than a 30 mm grain-size bed. Relying on the constant friction factor, Manning's n, is not recommended as it may result in design errors. These findings have the potential to improve hydraulic engineering design practices, enhancing the accuracy and efficiency of open-channel flow systems.},
}
RevDate: 2024-07-01
Entropy generation analysis and thermal synergy efficiency in the T-shaped micro-kenics.
Heliyon, 10(11):e32233.
In this work, three different twist angles of a micro helical insert in a T-shaped are studied numerically in order to evaluate the laminar steady flow behavior of Newtonian fluid in chaotic geometry. In the geometries under consideration, thermal mixing behavior is carried out using fluids having two distinct input temperatures. Under the influence of chaotic advection and low rates of Reynolds number, the second law of thermodynamics is controlled in terms of the entropy generation caused by hydrodynamic and thermal processes. The governing equations are numerically solved using the CFD Fluent code. Thus, the micromixer's configuration demonstrated a very significant improvement in mixing degree while minimizing friction and thermal irreversibilities. The synergy coefficient, which depicts the link between velocity and heat transfer in angle form, is analyzed and the results are provided.
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@article {pmid38947451,
year = {2024},
author = {Mahammedi, A and Tayeb, NT and Kim, JH and Hossain, S},
title = {Entropy generation analysis and thermal synergy efficiency in the T-shaped micro-kenics.},
journal = {Heliyon},
volume = {10},
number = {11},
pages = {e32233},
pmid = {38947451},
issn = {2405-8440},
abstract = {In this work, three different twist angles of a micro helical insert in a T-shaped are studied numerically in order to evaluate the laminar steady flow behavior of Newtonian fluid in chaotic geometry. In the geometries under consideration, thermal mixing behavior is carried out using fluids having two distinct input temperatures. Under the influence of chaotic advection and low rates of Reynolds number, the second law of thermodynamics is controlled in terms of the entropy generation caused by hydrodynamic and thermal processes. The governing equations are numerically solved using the CFD Fluent code. Thus, the micromixer's configuration demonstrated a very significant improvement in mixing degree while minimizing friction and thermal irreversibilities. The synergy coefficient, which depicts the link between velocity and heat transfer in angle form, is analyzed and the results are provided.},
}
RevDate: 2024-06-27
Machine learning analysis of thermophysical and thermohydraulic properties in ethylene glycol- and glycerol-based SiO2 nanofluids.
Scientific reports, 14(1):14829.
The study investigates the heat transfer and friction factor properties of ethylene glycol and glycerol-based silicon dioxide nanofluids flowing in a circular tube under continuous heat flux circumstances. This study tackles the important requirement for effective thermal management in areas such as electronics cooling, the automobile industry, and renewable energy systems. Previous research has encountered difficulties in enhancing thermal performance while handling the increased friction factor associated with nanofluids. This study conducted experiments in the Reynolds number range of 1300 to 21,000 with particle volume concentrations of up to 1.0%. Nanofluids exhibited superior heat transfer coefficients and friction factor values than the base liquid values. The highest enhancement in heat transfer was 5.4% and 8.3% for glycerol and ethylene glycol -based silicon dioxide Nanofluid with a relative friction factor penalty of ∼30% and 75%, respectively. To model and predict the complicated, nonlinear experimental data, five machine learning approaches were used: linear regression, random forest, extreme gradient boosting, adaptive boosting, and decision tree. Among them, the decision tree-based model performed well with few errors, while the random forest and extreme gradient boosting models were also highly accurate. The findings indicate that these advanced machine learning models can accurately anticipate the thermal performance of nanofluids, providing a dependable tool for improving their use in a variety of thermal systems. This study's findings help to design more effective cooling solutions and improve the sustainability of energy systems.
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@article {pmid38937518,
year = {2024},
author = {Akilu, S and Sharma, KV and Baheta, AT and Kanti, PK and Paramasivam, P},
title = {Machine learning analysis of thermophysical and thermohydraulic properties in ethylene glycol- and glycerol-based SiO2 nanofluids.},
journal = {Scientific reports},
volume = {14},
number = {1},
pages = {14829},
pmid = {38937518},
issn = {2045-2322},
abstract = {The study investigates the heat transfer and friction factor properties of ethylene glycol and glycerol-based silicon dioxide nanofluids flowing in a circular tube under continuous heat flux circumstances. This study tackles the important requirement for effective thermal management in areas such as electronics cooling, the automobile industry, and renewable energy systems. Previous research has encountered difficulties in enhancing thermal performance while handling the increased friction factor associated with nanofluids. This study conducted experiments in the Reynolds number range of 1300 to 21,000 with particle volume concentrations of up to 1.0%. Nanofluids exhibited superior heat transfer coefficients and friction factor values than the base liquid values. The highest enhancement in heat transfer was 5.4% and 8.3% for glycerol and ethylene glycol -based silicon dioxide Nanofluid with a relative friction factor penalty of ∼30% and 75%, respectively. To model and predict the complicated, nonlinear experimental data, five machine learning approaches were used: linear regression, random forest, extreme gradient boosting, adaptive boosting, and decision tree. Among them, the decision tree-based model performed well with few errors, while the random forest and extreme gradient boosting models were also highly accurate. The findings indicate that these advanced machine learning models can accurately anticipate the thermal performance of nanofluids, providing a dependable tool for improving their use in a variety of thermal systems. This study's findings help to design more effective cooling solutions and improve the sustainability of energy systems.},
}
RevDate: 2024-06-27
A High-Aspect-Ratio Deterministic Lateral Displacement Array for High-Throughput Fractionation.
Micromachines, 15(6): pii:mi15060802.
Future industrial applications of microparticle fractionation with deterministic lateral displacement (DLD) devices are hindered by exceedingly low throughput rates. To enable the necessary high-volume flows, high flow velocities as well as high aspect ratios in DLD devices have to be investigated. However, no experimental studies have yet been conducted on the fractionation of bi-disperse suspensions containing particles below 10 µm with DLD at a Reynolds number (Re) above 60. Furthermore, devices with an aspect ratio of more than 4:1, which require advanced microfabrication, are not known in the DLD literature. Therefore, we developed a suitable process with deep reactive ion etching of silicon and anodic bonding of a glass lid to create pressure-resistant arrays. With a depth of 120 µm and a gap of 23 µm between posts, a high aspect ratio of 6:1 was realized, and devices were investigated using simulations and fractionation experiments. With the two-segmented array of 3° and 7° row shifts, critical diameters of 8 µm and 12 µm were calculated for low Re conditions, but it was already known that vortices behind the posts can shift these values to lower critical diameters. Suspensions with polystyrene particles in different combinations were injected with an overall flow rate of up to 15 mL/min, corresponding to Re values of up to 90. Suspensions containing particle combinations of 2 µm with 10 µm as well as 5 µm with 10 µm were successfully fractionated, even at the highest flow rate. Under these conditions, a slight widening of the displacement position was observed, but there was no further reduction in the critical size as it was for Re = 60. With an unprecedented fractionation throughput of nearly 1 L per hour, entirely new applications are being developed for chemical, pharmaceutical, and recycling technologies.
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@article {pmid38930772,
year = {2024},
author = {Kottmeier, J and Wullenweber, MS and Kampen, I and Kwade, A and Dietzel, A},
title = {A High-Aspect-Ratio Deterministic Lateral Displacement Array for High-Throughput Fractionation.},
journal = {Micromachines},
volume = {15},
number = {6},
pages = {},
doi = {10.3390/mi15060802},
pmid = {38930772},
issn = {2072-666X},
support = {SPP 2045//Deutsche Forschungsgemeinschaft/ ; },
abstract = {Future industrial applications of microparticle fractionation with deterministic lateral displacement (DLD) devices are hindered by exceedingly low throughput rates. To enable the necessary high-volume flows, high flow velocities as well as high aspect ratios in DLD devices have to be investigated. However, no experimental studies have yet been conducted on the fractionation of bi-disperse suspensions containing particles below 10 µm with DLD at a Reynolds number (Re) above 60. Furthermore, devices with an aspect ratio of more than 4:1, which require advanced microfabrication, are not known in the DLD literature. Therefore, we developed a suitable process with deep reactive ion etching of silicon and anodic bonding of a glass lid to create pressure-resistant arrays. With a depth of 120 µm and a gap of 23 µm between posts, a high aspect ratio of 6:1 was realized, and devices were investigated using simulations and fractionation experiments. With the two-segmented array of 3° and 7° row shifts, critical diameters of 8 µm and 12 µm were calculated for low Re conditions, but it was already known that vortices behind the posts can shift these values to lower critical diameters. Suspensions with polystyrene particles in different combinations were injected with an overall flow rate of up to 15 mL/min, corresponding to Re values of up to 90. Suspensions containing particle combinations of 2 µm with 10 µm as well as 5 µm with 10 µm were successfully fractionated, even at the highest flow rate. Under these conditions, a slight widening of the displacement position was observed, but there was no further reduction in the critical size as it was for Re = 60. With an unprecedented fractionation throughput of nearly 1 L per hour, entirely new applications are being developed for chemical, pharmaceutical, and recycling technologies.},
}
RevDate: 2024-06-27
Mixing Performance of a Passive Micromixer Based on Split-to-Circulate (STC) Flow Characteristics.
Micromachines, 15(6): pii:mi15060773.
We propose a novel passive micromixer leveraging STC (split-to-circulate) flow characteristics and analyze its mixing performance comprehensively. Three distinct designs incorporating submerged circular walls were explored to achieve STC flow characteristics, facilitating flow along a convex surface and flow impingement on a concave surface. Across a broad Reynolds number range (0.1 to 80), the present micromixer substantially enhances mixing, with a degree of mixing (DOM) consistently exceeding 0.84. Particularly, the mixing enhancement is prominent within the low and intermediate range of Reynolds numbers (0.1
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@article {pmid38930743,
year = {2024},
author = {Juraeva, M and Kang, DJ},
title = {Mixing Performance of a Passive Micromixer Based on Split-to-Circulate (STC) Flow Characteristics.},
journal = {Micromachines},
volume = {15},
number = {6},
pages = {},
doi = {10.3390/mi15060773},
pmid = {38930743},
issn = {2072-666X},
abstract = {We propose a novel passive micromixer leveraging STC (split-to-circulate) flow characteristics and analyze its mixing performance comprehensively. Three distinct designs incorporating submerged circular walls were explored to achieve STC flow characteristics, facilitating flow along a convex surface and flow impingement on a concave surface. Across a broad Reynolds number range (0.1 to 80), the present micromixer substantially enhances mixing, with a degree of mixing (DOM) consistently exceeding 0.84. Particularly, the mixing enhancement is prominent within the low and intermediate range of Reynolds numbers (0.1
RevDate: 2024-06-27
Behind the Non-Uniform Breakup of Bubble Slug in Y-Shaped Microchannel: Dynamics and Mechanisms.
Micromachines, 15(6): pii:mi15060695.
Bubble flow in confined geometries is a problem of fundamental and technological significance. Among all the forms, bubble breakup in bifurcated microchannels is one of the most commonly encountered scenarios, where an in-depth understanding is necessary for better leveraging the process. This study numerically investigates the non-uniform breakup of a bubble slug in Y-shaped microchannels under different flow ratios, Reynolds numbers, and initial bubble volumes. Overall, the bubble can either breakup or non-breakup when passing through the bifurcation and shows different forms depending on flow regimes. The flow ratio-Reynolds number phase diagrams indicate a power-law transition line of breakup and non-breakup. The bubble takes longer to break up with rising flow ratios yet breaks earlier with higher Reynolds numbers and volumes. Non-breakup takes less time than the breakup patterns. Flow ratio is the origin of non-uniform breakup. Both the Reynolds number and initial volume influence the bubble states when reaching the bifurcation and thus affect subsequent processes. Bubble neck dynamics are analyzed to describe the breakup further. The volume distribution after breaking up is found to have a quadratic relation with the flow ratio. Our study is hoped to provide insights for practical applications related to non-uniform bubble breakups.
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@article {pmid38930665,
year = {2024},
author = {Huang, H and Liu, J and Yu, J and Pan, W and Yan, Z and Pan, Z},
title = {Behind the Non-Uniform Breakup of Bubble Slug in Y-Shaped Microchannel: Dynamics and Mechanisms.},
journal = {Micromachines},
volume = {15},
number = {6},
pages = {},
doi = {10.3390/mi15060695},
pmid = {38930665},
issn = {2072-666X},
abstract = {Bubble flow in confined geometries is a problem of fundamental and technological significance. Among all the forms, bubble breakup in bifurcated microchannels is one of the most commonly encountered scenarios, where an in-depth understanding is necessary for better leveraging the process. This study numerically investigates the non-uniform breakup of a bubble slug in Y-shaped microchannels under different flow ratios, Reynolds numbers, and initial bubble volumes. Overall, the bubble can either breakup or non-breakup when passing through the bifurcation and shows different forms depending on flow regimes. The flow ratio-Reynolds number phase diagrams indicate a power-law transition line of breakup and non-breakup. The bubble takes longer to break up with rising flow ratios yet breaks earlier with higher Reynolds numbers and volumes. Non-breakup takes less time than the breakup patterns. Flow ratio is the origin of non-uniform breakup. Both the Reynolds number and initial volume influence the bubble states when reaching the bifurcation and thus affect subsequent processes. Bubble neck dynamics are analyzed to describe the breakup further. The volume distribution after breaking up is found to have a quadratic relation with the flow ratio. Our study is hoped to provide insights for practical applications related to non-uniform bubble breakups.},
}
RevDate: 2024-06-27
A Review of Pressure Drop and Mixing Characteristics in Passive Mixers Involving Miscible Liquids.
Micromachines, 15(6): pii:mi15060691.
The present review focuses on the recent studies carried out in passive micromixers for understanding the hydrodynamics and transport phenomena of miscible liquid-liquid (LL) systems in terms of pressure drop and mixing indices. First, the passive micromixers have been categorized based on the type of complexity in shape, size, and configuration. It is observed that the use of different aspect ratios of the microchannel width, presence of obstructions, flow and operating conditions, and fluid properties majorly affect the mixing characteristics and pressure drop in passive micromixers. A regime map for the micromixer selection based on optimization of mixing index (MI) and pressure drop has been identified based on the literature data for the Reynolds number (Re) range (1 ≤ Re ≤ 100). The map comprehensively summarizes the favorable, moderately favorable, or non-operable regimes of a micromixer. Further, regions for special applications of complex micromixer shapes and micromixers operating at low Re have been identified. Similarly, the operable limits for a micromixer based on pressure drop for Re range 0.1 < Re < 100,000 have been identified. A comparison of measured pressure drop with fundamentally derived analytical expressions show that Category 3 and 4 micromixers mostly have higher pressure drops, except for a few efficient ones. An MI regime map comprising diffusion, chaotic advection, and mixed advection-dominated zones has also been devised. An empirical correlation for pressure drop as a function of Reynolds number has been developed and a corresponding friction factor has been obtained. Predictions on heat and mass transfer based on analogies in micromixers have also been proposed.
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@article {pmid38930661,
year = {2024},
author = {Ganguli, A and Bhatt, V and Yagodnitsyna, A and Pinjari, D and Pandit, A},
title = {A Review of Pressure Drop and Mixing Characteristics in Passive Mixers Involving Miscible Liquids.},
journal = {Micromachines},
volume = {15},
number = {6},
pages = {},
doi = {10.3390/mi15060691},
pmid = {38930661},
issn = {2072-666X},
abstract = {The present review focuses on the recent studies carried out in passive micromixers for understanding the hydrodynamics and transport phenomena of miscible liquid-liquid (LL) systems in terms of pressure drop and mixing indices. First, the passive micromixers have been categorized based on the type of complexity in shape, size, and configuration. It is observed that the use of different aspect ratios of the microchannel width, presence of obstructions, flow and operating conditions, and fluid properties majorly affect the mixing characteristics and pressure drop in passive micromixers. A regime map for the micromixer selection based on optimization of mixing index (MI) and pressure drop has been identified based on the literature data for the Reynolds number (Re) range (1 ≤ Re ≤ 100). The map comprehensively summarizes the favorable, moderately favorable, or non-operable regimes of a micromixer. Further, regions for special applications of complex micromixer shapes and micromixers operating at low Re have been identified. Similarly, the operable limits for a micromixer based on pressure drop for Re range 0.1 < Re < 100,000 have been identified. A comparison of measured pressure drop with fundamentally derived analytical expressions show that Category 3 and 4 micromixers mostly have higher pressure drops, except for a few efficient ones. An MI regime map comprising diffusion, chaotic advection, and mixed advection-dominated zones has also been devised. An empirical correlation for pressure drop as a function of Reynolds number has been developed and a corresponding friction factor has been obtained. Predictions on heat and mass transfer based on analogies in micromixers have also been proposed.},
}
RevDate: 2024-06-26
Entropy Fluctuations and Correlations in Compressible Turbulent Plane Channel Flow.
Entropy (Basel, Switzerland), 26(6): pii:e26060530.
The thermodynamic turbulence structure of compressible aerodynamic flows is often characterised by the correlation coefficient of entropy with pressure or temperature. We study entropy fluctuations s' and their correlations with the fluctuations of the other thermodynamic variables in compressible turbulent plane channel flow using dns data. We investigate the influence of the hcb (Huang-Coleman-Bradshaw) friction Reynolds number (100⪅Reτ★⪅1000) and of the centreline Mach number (0.3⪅M¯CLx⪅2.5) on the magnitude and location of the peak of the root-mean-square srms'. The complete series expansions of s' with respect to the fluctuations of the basic thermodynamic variables (pressure p, density ρ and temperature T) are calculated for the general case of variable heat-capacity cp(T) thermodynamics. The correlation coefficients of s' with the fluctuations of the basic thermodynamic quantities (cs'p', cs'ρ', cs'T'), for varying (Reτ★,M¯CLx), are studied. Insight on these correlations is provided by considering the probability density function (pdf) of s' and its joint pdfs with the other thermodynamic variables.
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@article {pmid38920538,
year = {2024},
author = {Gerolymos, GA and Vallet, I},
title = {Entropy Fluctuations and Correlations in Compressible Turbulent Plane Channel Flow.},
journal = {Entropy (Basel, Switzerland)},
volume = {26},
number = {6},
pages = {},
doi = {10.3390/e26060530},
pmid = {38920538},
issn = {1099-4300},
support = {2023-022139, 2022-022139, 2021-022139, 2020-022139, 2019-022139, 2018-022139 TGCC-CINES-IDRIS//Grand Équipement National de Calcul Intensif (France)/ ; 2021-240083 JUWELS//Partnership for Advanced Computing in Europe/ ; ANR-15-CE06-0009 NumERICCS//Agence Nationale de la Recherche/ ; },
abstract = {The thermodynamic turbulence structure of compressible aerodynamic flows is often characterised by the correlation coefficient of entropy with pressure or temperature. We study entropy fluctuations s' and their correlations with the fluctuations of the other thermodynamic variables in compressible turbulent plane channel flow using dns data. We investigate the influence of the hcb (Huang-Coleman-Bradshaw) friction Reynolds number (100⪅Reτ★⪅1000) and of the centreline Mach number (0.3⪅M¯CLx⪅2.5) on the magnitude and location of the peak of the root-mean-square srms'. The complete series expansions of s' with respect to the fluctuations of the basic thermodynamic variables (pressure p, density ρ and temperature T) are calculated for the general case of variable heat-capacity cp(T) thermodynamics. The correlation coefficients of s' with the fluctuations of the basic thermodynamic quantities (cs'p', cs'ρ', cs'T'), for varying (Reτ★,M¯CLx), are studied. Insight on these correlations is provided by considering the probability density function (pdf) of s' and its joint pdfs with the other thermodynamic variables.},
}
RevDate: 2024-06-26
Elasto-inertial focusing and particle migration in high aspect ratio microchannels for high-throughput separation.
Microsystems & nanoengineering, 10:87.
The combination of flow elasticity and inertia has emerged as a viable tool for focusing and manipulating particles using microfluidics. Although there is considerable interest in the field of elasto-inertial microfluidics owing to its potential applications, research on particle focusing has been mostly limited to low Reynolds numbers (Re<1), and particle migration toward equilibrium positions has not been extensively examined. In this work, we thoroughly studied particle focusing on the dynamic range of flow rates and particle migration using straight microchannels with a single inlet high aspect ratio. We initially explored several parameters that had an impact on particle focusing, such as the particle size, channel dimensions, concentration of viscoelastic fluid, and flow rate. Our experimental work covered a wide range of dimensionless numbers (0.05 < Reynolds number < 85, 1.5 < Weissenberg number < 3800, 5 < Elasticity number < 470) using 3, 5, 7, and 10 µm particles. Our results showed that the particle size played a dominant role, and by tuning the parameters, particle focusing could be achieved at Reynolds numbers ranging from 0.2 (1 µL/min) to 85 (250 µL/min). Furthermore, we numerically and experimentally studied particle migration and reported differential particle migration for high-resolution separations of 5 µm, 7 µm and 10 µm particles in a sheathless flow at a throughput of 150 µL/min. Our work elucidates the complex particle transport in elasto-inertial flows and has great potential for the development of high-throughput and high-resolution particle separation for biomedical and environmental applications.
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@article {pmid38919163,
year = {2024},
author = {Tanriverdi, S and Cruz, J and Habibi, S and Amini, K and Costa, M and Lundell, F and Mårtensson, G and Brandt, L and Tammisola, O and Russom, A},
title = {Elasto-inertial focusing and particle migration in high aspect ratio microchannels for high-throughput separation.},
journal = {Microsystems & nanoengineering},
volume = {10},
number = {},
pages = {87},
pmid = {38919163},
issn = {2055-7434},
abstract = {The combination of flow elasticity and inertia has emerged as a viable tool for focusing and manipulating particles using microfluidics. Although there is considerable interest in the field of elasto-inertial microfluidics owing to its potential applications, research on particle focusing has been mostly limited to low Reynolds numbers (Re<1), and particle migration toward equilibrium positions has not been extensively examined. In this work, we thoroughly studied particle focusing on the dynamic range of flow rates and particle migration using straight microchannels with a single inlet high aspect ratio. We initially explored several parameters that had an impact on particle focusing, such as the particle size, channel dimensions, concentration of viscoelastic fluid, and flow rate. Our experimental work covered a wide range of dimensionless numbers (0.05 < Reynolds number < 85, 1.5 < Weissenberg number < 3800, 5 < Elasticity number < 470) using 3, 5, 7, and 10 µm particles. Our results showed that the particle size played a dominant role, and by tuning the parameters, particle focusing could be achieved at Reynolds numbers ranging from 0.2 (1 µL/min) to 85 (250 µL/min). Furthermore, we numerically and experimentally studied particle migration and reported differential particle migration for high-resolution separations of 5 µm, 7 µm and 10 µm particles in a sheathless flow at a throughput of 150 µL/min. Our work elucidates the complex particle transport in elasto-inertial flows and has great potential for the development of high-throughput and high-resolution particle separation for biomedical and environmental applications.},
}
RevDate: 2024-06-22
Emergence of inertia in the low-Reynolds regime of self-diffusiophoretic motion.
Physical review. E, 109(5-1):054602.
For isotropic swimming particles driven by self-diffusiophoresis at zero Reynolds number (where particle velocity responds instantaneously to applied force), the diffusive timescale of emitted solute can produce an emergent quasi-inertial behavior. These particles can orbit in a central potential and reorient under second-order dynamics, not the first-order dynamics of classical zero-Reynolds motion. They are described by a simple effective model that embeds their history-dependent behavior as an effective inertia, this being the most primitive expression of memory. The system can be parameterized with dynamic quantities such as particle size and swimming speed, without detailed knowledge of the diffusiophoretic mechanism.
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@article {pmid38907454,
year = {2024},
author = {Zero, EN and Crespi, VH},
title = {Emergence of inertia in the low-Reynolds regime of self-diffusiophoretic motion.},
journal = {Physical review. E},
volume = {109},
number = {5-1},
pages = {054602},
doi = {10.1103/PhysRevE.109.054602},
pmid = {38907454},
issn = {2470-0053},
abstract = {For isotropic swimming particles driven by self-diffusiophoresis at zero Reynolds number (where particle velocity responds instantaneously to applied force), the diffusive timescale of emitted solute can produce an emergent quasi-inertial behavior. These particles can orbit in a central potential and reorient under second-order dynamics, not the first-order dynamics of classical zero-Reynolds motion. They are described by a simple effective model that embeds their history-dependent behavior as an effective inertia, this being the most primitive expression of memory. The system can be parameterized with dynamic quantities such as particle size and swimming speed, without detailed knowledge of the diffusiophoretic mechanism.},
}
RevDate: 2024-06-21
Heavy Particle Clustering in Inertial Subrange of High-Reynolds Number Turbulence.
Physical review letters, 132(23):234001.
Direct numerical simulation of homogeneous isotropic turbulence shows pronounced clustering of inertial particles in the inertial subrange at high Reynolds number, in addition to the clustering typically observed in the near dissipation range. The clustering in the inertial subrange is characterized by the bump in the particle number density spectra and is due to modulation of preferential concentration. The number density spectrum can be modeled by a rational function of the scale-dependent Stokes number.
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@article {pmid38905672,
year = {2024},
author = {Matsuda, K and Yoshimatsu, K and Schneider, K},
title = {Heavy Particle Clustering in Inertial Subrange of High-Reynolds Number Turbulence.},
journal = {Physical review letters},
volume = {132},
number = {23},
pages = {234001},
doi = {10.1103/PhysRevLett.132.234001},
pmid = {38905672},
issn = {1079-7114},
abstract = {Direct numerical simulation of homogeneous isotropic turbulence shows pronounced clustering of inertial particles in the inertial subrange at high Reynolds number, in addition to the clustering typically observed in the near dissipation range. The clustering in the inertial subrange is characterized by the bump in the particle number density spectra and is due to modulation of preferential concentration. The number density spectrum can be modeled by a rational function of the scale-dependent Stokes number.},
}
RevDate: 2024-06-20
Analysis of the number of topological defects in active nematic fluids under applied shear flow.
The European physical journal. E, Soft matter, 47(6):43.
The number of topological defects in the shear flow of active nematic fluids is numerically investigated in this study. The evolution of the flow state of extensile active nematic fluids is explored by increasing the activity of active nematic fluids. Evidently, medium-activity active nematic fluids exhibit a highly ordered vortex lattice fluid state. However, high-activity active nematic fluids exhibit a meso-scale turbulent flow accompanied by topological defects. The number of topological defects (Ndef) increases with increasing shear Reynolds number (Res). Fluid viscosity strongly influences Ndef, while the influence of fluid density is relatively weak. Ndef decreases with increasing activity length scale (lζ) value. A small Res value strongly influences Ndef, whereas a large lζ value only weakly influences Ndef. As the activity increases, Ndef in contractile active nematic fluids becomes larger than that of extensile active nematic fluids.
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@article {pmid38900310,
year = {2024},
author = {Li, Z and Ye, H and Lin, J and Ouyang, Z},
title = {Analysis of the number of topological defects in active nematic fluids under applied shear flow.},
journal = {The European physical journal. E, Soft matter},
volume = {47},
number = {6},
pages = {43},
pmid = {38900310},
issn = {1292-895X},
support = {12132015//Key Programme/ ; 12332015//Key Programme/ ; },
abstract = {The number of topological defects in the shear flow of active nematic fluids is numerically investigated in this study. The evolution of the flow state of extensile active nematic fluids is explored by increasing the activity of active nematic fluids. Evidently, medium-activity active nematic fluids exhibit a highly ordered vortex lattice fluid state. However, high-activity active nematic fluids exhibit a meso-scale turbulent flow accompanied by topological defects. The number of topological defects (Ndef) increases with increasing shear Reynolds number (Res). Fluid viscosity strongly influences Ndef, while the influence of fluid density is relatively weak. Ndef decreases with increasing activity length scale (lζ) value. A small Res value strongly influences Ndef, whereas a large lζ value only weakly influences Ndef. As the activity increases, Ndef in contractile active nematic fluids becomes larger than that of extensile active nematic fluids.},
}
RevDate: 2024-06-19
The Impact of Surface Roughness on Conformal Cooling Channels for Injection Molding.
Materials (Basel, Switzerland), 17(11):.
Injection molding technology is widely utilized across various industries for its ability to fabricate complex-shaped components with exceptional dimensional accuracy. However, challenges related to injection quality often arise, necessitating innovative approaches for improvement. This study investigates the influence of surface roughness on the efficiency of conformal cooling channels produced using additive manufacturing technologies, specifically Direct Metal Laser Sintering (DMLS) and Atomic Diffusion Additive Manufacturing (ADAM). Through a combination of experimental measurements, including surface roughness analysis, scanning electron microscopy, and cooling system flow analysis, this study elucidates the impact of surface roughness on coolant flow dynamics and pressure distribution within the cooling channels. The results reveal significant differences in surface roughness between DMLS and ADAM technologies, with corresponding effects on coolant flow behavior. Following that fact, this study shows that when cooling channels' surface roughness is lowered up to 90%, the reduction in coolant media pressure is lowered by 0.033 MPa. Regression models are developed to quantitatively describe the relationship between surface roughness and key parameters, such as coolant pressure, Reynolds number, and flow velocity. Practical implications for the optimization of injection molding cooling systems are discussed, highlighting the importance of informed decision making in technology selection and post-processing techniques. Overall, this research contributes to a deeper understanding of the role of surface roughness in injection molding processes and provides valuable insights for enhancing cooling system efficiency and product quality.
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@article {pmid38893741,
year = {2024},
author = {Hanzlik, J and Vanek, J and Pata, V and Senkerik, V and Polaskova, M and Kruzelak, J and Bednarik, M},
title = {The Impact of Surface Roughness on Conformal Cooling Channels for Injection Molding.},
journal = {Materials (Basel, Switzerland)},
volume = {17},
number = {11},
pages = {},
pmid = {38893741},
issn = {1996-1944},
support = {IGA/FT/2024/003//Internal Grant Agency of Tomas Bata University in Zlin/ ; },
abstract = {Injection molding technology is widely utilized across various industries for its ability to fabricate complex-shaped components with exceptional dimensional accuracy. However, challenges related to injection quality often arise, necessitating innovative approaches for improvement. This study investigates the influence of surface roughness on the efficiency of conformal cooling channels produced using additive manufacturing technologies, specifically Direct Metal Laser Sintering (DMLS) and Atomic Diffusion Additive Manufacturing (ADAM). Through a combination of experimental measurements, including surface roughness analysis, scanning electron microscopy, and cooling system flow analysis, this study elucidates the impact of surface roughness on coolant flow dynamics and pressure distribution within the cooling channels. The results reveal significant differences in surface roughness between DMLS and ADAM technologies, with corresponding effects on coolant flow behavior. Following that fact, this study shows that when cooling channels' surface roughness is lowered up to 90%, the reduction in coolant media pressure is lowered by 0.033 MPa. Regression models are developed to quantitatively describe the relationship between surface roughness and key parameters, such as coolant pressure, Reynolds number, and flow velocity. Practical implications for the optimization of injection molding cooling systems are discussed, highlighting the importance of informed decision making in technology selection and post-processing techniques. Overall, this research contributes to a deeper understanding of the role of surface roughness in injection molding processes and provides valuable insights for enhancing cooling system efficiency and product quality.},
}
RevDate: 2024-06-17
Turbulence model study for aerodynamic analysis of the leading edge tubercle wing for low Reynolds number flows.
Heliyon, 10(11):e32148.
A turbulence model study was performed to analyze the flow around the Tubercle Leading Edge (TLE) wing. Five turbulence models were selected to evaluate aerodynamic force coefficients and flow mechanism by comparing with existing literature results. The selected models are realizable k-ε, k-ω Shear Stress Transport (SST), (γ - R e θ) SST model, Transition k-k l -ω model and Stress- ω Reynolds Stress Model (RSM). For that purpose, the TLE wing model was developed by using the NACA0021 airfoil profile. The wing model is designed with tubercle wavelength of 0.11c and amplitude of 0.03c. Numerical simulation was performed at chord-based Reynolds number of Rec = 120,000. The Computational Fluid Dynamic (CFD) simulation reveals that among the selected turbulence models, Stress- ω RSM estimated aerodynamic forces (i.e. lift and drag) coefficients closest to that of the experimental values followed by realizable k-ε, (γ - R e θ) SST model, k-ω SST model and k-k l -ω model. However, at a higher angle of attacks i.e. at 16° & 20° k-ω SST model predicted closest drag and lift coefficient to that of the experimental values. Additionally, the critical observation of pressure contour confirmed that at the lower angle of attack Stress- ω RSM predicted strong Leading Edge (LE) suction followed by realizable k-ε, (γ - R e θ)SST model, k-ω SST model and k-k l -ω model. Thus, the superiority of Stress- ω RSM in predicting the aerodynamic force coefficients is shown by the flow behavior. In addition to this pressure contours also confirmed that k-k l -ω model failed to predict tubercled wing aerodynamic performance. At higher angles of attacks k-ω SST model estimated aerodynamic force coefficients closest to that of the experimental values, thus k-ω SST model is used at 16° & 20° AoAs. The observed streamline behavior for different turbulence models showed that the Stress- ω RSM model and k-k l -ω model failed to model flow behavior at higher AoAs, whereas k-ω SST model is a better approach to model separated flows that experience strong flow recirculation zone.
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@article {pmid38882326,
year = {2024},
author = {Ali, I and Hussain, T and Unar, IN and Kumar, L and Ahad, IU},
title = {Turbulence model study for aerodynamic analysis of the leading edge tubercle wing for low Reynolds number flows.},
journal = {Heliyon},
volume = {10},
number = {11},
pages = {e32148},
pmid = {38882326},
issn = {2405-8440},
abstract = {A turbulence model study was performed to analyze the flow around the Tubercle Leading Edge (TLE) wing. Five turbulence models were selected to evaluate aerodynamic force coefficients and flow mechanism by comparing with existing literature results. The selected models are realizable k-ε, k-ω Shear Stress Transport (SST), (γ - R e θ) SST model, Transition k-k l -ω model and Stress- ω Reynolds Stress Model (RSM). For that purpose, the TLE wing model was developed by using the NACA0021 airfoil profile. The wing model is designed with tubercle wavelength of 0.11c and amplitude of 0.03c. Numerical simulation was performed at chord-based Reynolds number of Rec = 120,000. The Computational Fluid Dynamic (CFD) simulation reveals that among the selected turbulence models, Stress- ω RSM estimated aerodynamic forces (i.e. lift and drag) coefficients closest to that of the experimental values followed by realizable k-ε, (γ - R e θ) SST model, k-ω SST model and k-k l -ω model. However, at a higher angle of attacks i.e. at 16° & 20° k-ω SST model predicted closest drag and lift coefficient to that of the experimental values. Additionally, the critical observation of pressure contour confirmed that at the lower angle of attack Stress- ω RSM predicted strong Leading Edge (LE) suction followed by realizable k-ε, (γ - R e θ)SST model, k-ω SST model and k-k l -ω model. Thus, the superiority of Stress- ω RSM in predicting the aerodynamic force coefficients is shown by the flow behavior. In addition to this pressure contours also confirmed that k-k l -ω model failed to predict tubercled wing aerodynamic performance. At higher angles of attacks k-ω SST model estimated aerodynamic force coefficients closest to that of the experimental values, thus k-ω SST model is used at 16° & 20° AoAs. The observed streamline behavior for different turbulence models showed that the Stress- ω RSM model and k-k l -ω model failed to model flow behavior at higher AoAs, whereas k-ω SST model is a better approach to model separated flows that experience strong flow recirculation zone.},
}
RevDate: 2024-06-10
CmpDate: 2024-06-10
Enhanced microfluidic multi-target separation by positive and negative magnetophoresis.
Scientific reports, 14(1):13293.
We introduce magnetophoresis-based microfluidics for sorting biological targets using positive Magnetophoresis (pM) for magnetically labeled particles and negative Magnetophoresis (nM) for label-free particles. A single, externally magnetized ferromagnetic wire induces repulsive forces and is positioned across the focused sample flow near the main channel's closed end. We analyze magnetic attributes and separation performance under two transverse dual-mode magnetic configurations, examining magnetic fields, hydrodynamics, and forces on microparticles of varying sizes and properties. In pM, the dual-magnet arrangement (DMA) for sorting three distinct particles shows higher magnetic gradient generation and throughput than the single-magnet arrangement (SMA). In nM, the numerical results for SMA sorting of red blood cells (RBCs), white blood cells (WBCs), and prostate cancer cells (PC3-9) demonstrate superior magnetic properties and throughput compared to DMA. Magnetized wire linear movement is a key design parameter, allowing device customization. An automated device for handling more targets can be created by manipulating magnetophoretic repulsion forces. The transverse wire and magnet arrangement accommodate increased channel depth without sacrificing efficiency, yielding higher throughput than other devices. Experimental validation using soft lithography and 3D printing confirms successful sorting and separation, aligning well with numerical results. This demonstrates the successful sorting and separating of injected particles within a hydrodynamically focused sample in all systems. Both numerical and experimental findings indicate a separation accuracy of 100% across various Reynolds numbers. The primary channel dimensions measure 100 µm in height and 200 µm in width. N52 permanent magnets were employed in both numerical simulations and experiments. For numerical simulations, a remanent flux density of 1.48 T was utilized. In the experimental setup, magnets measuring 0.5 × 0.5 × 0.125 inches and 0.5 × 0.5 × 1 inch were employed. The experimental data confirm the device's capability to achieve 100% separation accuracy at a Reynolds number of 3. However, this study did not explore the potential impact of increased flow rates on separation accuracy.
Additional Links: PMID-38858424
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@article {pmid38858424,
year = {2024},
author = {Khashan, S and Odhah, AA and Taha, M and Alazzam, A and Al-Fandi, M},
title = {Enhanced microfluidic multi-target separation by positive and negative magnetophoresis.},
journal = {Scientific reports},
volume = {14},
number = {1},
pages = {13293},
pmid = {38858424},
issn = {2045-2322},
support = {ENG/1/13/2018//Scientific Research and Innovation Support Fund (SRSF)/ ; },
mesh = {Humans ; *Microfluidic Analytical Techniques/instrumentation/methods ; Cell Separation/methods/instrumentation ; Erythrocytes ; Microfluidics/methods/instrumentation ; Leukocytes ; Hydrodynamics ; Cell Line, Tumor ; },
abstract = {We introduce magnetophoresis-based microfluidics for sorting biological targets using positive Magnetophoresis (pM) for magnetically labeled particles and negative Magnetophoresis (nM) for label-free particles. A single, externally magnetized ferromagnetic wire induces repulsive forces and is positioned across the focused sample flow near the main channel's closed end. We analyze magnetic attributes and separation performance under two transverse dual-mode magnetic configurations, examining magnetic fields, hydrodynamics, and forces on microparticles of varying sizes and properties. In pM, the dual-magnet arrangement (DMA) for sorting three distinct particles shows higher magnetic gradient generation and throughput than the single-magnet arrangement (SMA). In nM, the numerical results for SMA sorting of red blood cells (RBCs), white blood cells (WBCs), and prostate cancer cells (PC3-9) demonstrate superior magnetic properties and throughput compared to DMA. Magnetized wire linear movement is a key design parameter, allowing device customization. An automated device for handling more targets can be created by manipulating magnetophoretic repulsion forces. The transverse wire and magnet arrangement accommodate increased channel depth without sacrificing efficiency, yielding higher throughput than other devices. Experimental validation using soft lithography and 3D printing confirms successful sorting and separation, aligning well with numerical results. This demonstrates the successful sorting and separating of injected particles within a hydrodynamically focused sample in all systems. Both numerical and experimental findings indicate a separation accuracy of 100% across various Reynolds numbers. The primary channel dimensions measure 100 µm in height and 200 µm in width. N52 permanent magnets were employed in both numerical simulations and experiments. For numerical simulations, a remanent flux density of 1.48 T was utilized. In the experimental setup, magnets measuring 0.5 × 0.5 × 0.125 inches and 0.5 × 0.5 × 1 inch were employed. The experimental data confirm the device's capability to achieve 100% separation accuracy at a Reynolds number of 3. However, this study did not explore the potential impact of increased flow rates on separation accuracy.},
}
MeSH Terms:
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Humans
*Microfluidic Analytical Techniques/instrumentation/methods
Cell Separation/methods/instrumentation
Erythrocytes
Microfluidics/methods/instrumentation
Leukocytes
Hydrodynamics
Cell Line, Tumor
RevDate: 2024-06-10
CmpDate: 2024-06-10
Harnessing flow-induced vibrations for energy harvesting: Experimental and numerical insights using piezoelectric transducer.
PloS one, 19(6):e0304489 pii:PONE-D-24-02616.
Flow-induced vibrations (FIV) were considered as unwanted vibrations analogous to noise. However, in a recent trend, the energy of these vibrations can be harvested and converted to electrical power. In this study, the potential of FIV as a source of renewable energy is highlighted through experimental and numerical analyses. The experimental study was conducted on an elastically mounted circular cylinder using helical and leaf springs in the wind tunnel. The Reynolds number (Re) varied between 2300-16000. The motion of the cylinder was restricted in all directions except the transverse direction. The micro-electromechanical system (MEMS) was mounted on the leaf spring to harvest the mechanical energy. Numerical simulations were also performed with SST k-ω turbulence model to supplement the experiments and were found to be in good agreement with the experimental results. The flow separation and vortex shedding induce aerodynamic forces in the cylinder causing it to vibrate. 2S vortex shedding pattern was observed in all of the cases in this study. The maximum dimensionless amplitude of vibration (A/D) obtained was 0.084 and 0.068 experimentally and numerically, respectively. The results showed that the region of interest is the lock-in region where maximum amplitude of vibration is observed and, therefore, the maximum power output. The piezoelectric voltage and power output were recorded for different reduced velocities (Ur = 1-10) at different resistance values in the circuit. It was observed that as the amplitude of oscillation of the cylinder increases, the voltage and power output of the MEMS increases due to high strain in piezoelectric transducer. The maximum output voltage of 0.6V was observed at Ur = 4.95 for an open circuit, i.e., for a circuit with the resistance value of infinity. As the resistance value reduced, a drop in voltage output was observed. Maximum power of 10.5μW was recorded at Ur = 4.95 for a circuit resistance of 100Ω.
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@article {pmid38857262,
year = {2024},
author = {Islam, M and Ali, U and Mone, S},
title = {Harnessing flow-induced vibrations for energy harvesting: Experimental and numerical insights using piezoelectric transducer.},
journal = {PloS one},
volume = {19},
number = {6},
pages = {e0304489},
doi = {10.1371/journal.pone.0304489},
pmid = {38857262},
issn = {1932-6203},
mesh = {*Vibration ; *Transducers ; Models, Theoretical ; Renewable Energy ; Micro-Electrical-Mechanical Systems/instrumentation ; Computer Simulation ; },
abstract = {Flow-induced vibrations (FIV) were considered as unwanted vibrations analogous to noise. However, in a recent trend, the energy of these vibrations can be harvested and converted to electrical power. In this study, the potential of FIV as a source of renewable energy is highlighted through experimental and numerical analyses. The experimental study was conducted on an elastically mounted circular cylinder using helical and leaf springs in the wind tunnel. The Reynolds number (Re) varied between 2300-16000. The motion of the cylinder was restricted in all directions except the transverse direction. The micro-electromechanical system (MEMS) was mounted on the leaf spring to harvest the mechanical energy. Numerical simulations were also performed with SST k-ω turbulence model to supplement the experiments and were found to be in good agreement with the experimental results. The flow separation and vortex shedding induce aerodynamic forces in the cylinder causing it to vibrate. 2S vortex shedding pattern was observed in all of the cases in this study. The maximum dimensionless amplitude of vibration (A/D) obtained was 0.084 and 0.068 experimentally and numerically, respectively. The results showed that the region of interest is the lock-in region where maximum amplitude of vibration is observed and, therefore, the maximum power output. The piezoelectric voltage and power output were recorded for different reduced velocities (Ur = 1-10) at different resistance values in the circuit. It was observed that as the amplitude of oscillation of the cylinder increases, the voltage and power output of the MEMS increases due to high strain in piezoelectric transducer. The maximum output voltage of 0.6V was observed at Ur = 4.95 for an open circuit, i.e., for a circuit with the resistance value of infinity. As the resistance value reduced, a drop in voltage output was observed. Maximum power of 10.5μW was recorded at Ur = 4.95 for a circuit resistance of 100Ω.},
}
MeSH Terms:
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*Vibration
*Transducers
Models, Theoretical
Renewable Energy
Micro-Electrical-Mechanical Systems/instrumentation
Computer Simulation
RevDate: 2024-06-06
Fluid-particle-structure interaction in single shot peening.
Scientific reports, 14(1):13029.
Shot peening is a widely used cold-working process. Physical phenomena of shot peening are analyzed using the developed fluid-particle-structure coupled solver. The influences of the flow field and shot peening parameters such as the shot impact velocity and shot size are investigated in the case of the falling, impacting, and rebounding single particle. The weakly coupled solver applies the immersed boundary method which enables direct evaluation of the interactions between the unsteady flow field and moving/deforming objects. The elastoplastic object of AISI4340 during the collision of rigid steel shot is analyzed dynamically using the finite element method. Consequently, it is clarified that the flow field of the post-collision between the shot and structure can be characterized by the relative Reynolds number, which is based on the shot diameter and relative velocity between the uniform flow and rebounding shot velocities. As the relative Reynolds number increases, the complex flow field and vortex structures are generated at the collision location. These fluid structures affect the collision phenomena resulting in the random behavior of the shot and the asymmetric indentation in the structure.
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@article {pmid38844512,
year = {2024},
author = {Mizuno, Y and Misaka, T and Furukawa, Y},
title = {Fluid-particle-structure interaction in single shot peening.},
journal = {Scientific reports},
volume = {14},
number = {1},
pages = {13029},
pmid = {38844512},
issn = {2045-2322},
abstract = {Shot peening is a widely used cold-working process. Physical phenomena of shot peening are analyzed using the developed fluid-particle-structure coupled solver. The influences of the flow field and shot peening parameters such as the shot impact velocity and shot size are investigated in the case of the falling, impacting, and rebounding single particle. The weakly coupled solver applies the immersed boundary method which enables direct evaluation of the interactions between the unsteady flow field and moving/deforming objects. The elastoplastic object of AISI4340 during the collision of rigid steel shot is analyzed dynamically using the finite element method. Consequently, it is clarified that the flow field of the post-collision between the shot and structure can be characterized by the relative Reynolds number, which is based on the shot diameter and relative velocity between the uniform flow and rebounding shot velocities. As the relative Reynolds number increases, the complex flow field and vortex structures are generated at the collision location. These fluid structures affect the collision phenomena resulting in the random behavior of the shot and the asymmetric indentation in the structure.},
}
RevDate: 2024-06-04
Influence of vegetation on heavy metal Cr release process from bottom sediment under unidirectional flows and regular waves.
Marine pollution bulletin, 204:116535 pii:S0025-326X(24)00512-5 [Epub ahead of print].
As human activities become more intensive, a substantial number of heavy metals are discharged into estuarine or wetland environments. Due to the poor degradability, heavy metals are prone to adsorption and deposition on suspended particles in bottom sediments. Subsequently, under the influence of disturbances, there is a potential for their re-release, causing secondary pollution. To investigate the release process of the heavy metal Cr from sediment, laboratory experiments were conducted under both unidirectional flow and regular wave conditions. At the initial stage, the temporal trends of particulate (CrP) and dissolved (CrD) Chromium concentrations were both characterized by initial increments followed by stabilization and continuous escalation. Vertically, the stable concentrations of CrP and CrD increased with the presence of vegetation and the enhancement of hydrodynamics. The Elovich equation, pseudo-second-order kinetic equation, Double constant equation (Freundlich model), and parabolic diffusion equation were employed to predict the release process of CrD from bottom sediment. The Elovich equation proved most suitable for describing the release process of CrD, with an R[2] exceeding 0.9. In order to assess the influence of vegetation on the Cr release process, the Stem-Reynolds were introduced to modify the Elovich equation. The final maximum error was 12 % (excluding the initial stage), which was much lower than that using the original Elovich equation (maximum error of 32 %). The study findings provide practical support for estuarine and wetland managers to formulate effective heavy metal management measures, which contribute to the conservation and sustainable management of aquatic ecosystems.
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@article {pmid38833948,
year = {2024},
author = {Lou, S and Zou, Y and Wang, H and Zhou, F and Liu, S and Tu, J and Fedorova, IV},
title = {Influence of vegetation on heavy metal Cr release process from bottom sediment under unidirectional flows and regular waves.},
journal = {Marine pollution bulletin},
volume = {204},
number = {},
pages = {116535},
doi = {10.1016/j.marpolbul.2024.116535},
pmid = {38833948},
issn = {1879-3363},
abstract = {As human activities become more intensive, a substantial number of heavy metals are discharged into estuarine or wetland environments. Due to the poor degradability, heavy metals are prone to adsorption and deposition on suspended particles in bottom sediments. Subsequently, under the influence of disturbances, there is a potential for their re-release, causing secondary pollution. To investigate the release process of the heavy metal Cr from sediment, laboratory experiments were conducted under both unidirectional flow and regular wave conditions. At the initial stage, the temporal trends of particulate (CrP) and dissolved (CrD) Chromium concentrations were both characterized by initial increments followed by stabilization and continuous escalation. Vertically, the stable concentrations of CrP and CrD increased with the presence of vegetation and the enhancement of hydrodynamics. The Elovich equation, pseudo-second-order kinetic equation, Double constant equation (Freundlich model), and parabolic diffusion equation were employed to predict the release process of CrD from bottom sediment. The Elovich equation proved most suitable for describing the release process of CrD, with an R[2] exceeding 0.9. In order to assess the influence of vegetation on the Cr release process, the Stem-Reynolds were introduced to modify the Elovich equation. The final maximum error was 12 % (excluding the initial stage), which was much lower than that using the original Elovich equation (maximum error of 32 %). The study findings provide practical support for estuarine and wetland managers to formulate effective heavy metal management measures, which contribute to the conservation and sustainable management of aquatic ecosystems.},
}
RevDate: 2024-05-29
Electromagnetohydrodynamic (EMHD) flow of Jeffrey fluid through a rough circular microchannel with surface charge-dependent slip.
Electrophoresis [Epub ahead of print].
This research examines the electromagnetohydrodynamic (EMHD) flow of Jeffrey fluid in a rough circular microchannel while considering the effect of surface charge on slip. The channel wall corrugations are described as periodic sinusoidal waves with small amplitudes. The perturbation method is employed to derive solutions for velocity and volumetric flow rate, and a combination of three-dimensional (3D) and two-dimensional (2D) graphical representations is utilized to effectively illustrate the impacts of relevant parameters on them. The significance of the Reynolds number R e $Re$ in investigations of EMHD flow is particularly emphasized. Furthermore, the effect of wall roughness ε $\varepsilon $ and wave number k $k$ on velocity and the influence of wall roughness ε $\varepsilon $ and surface charge density σ s ${\sigma }_s$ on volumetric flow rate are primarily focused on, respectively, at various Reynolds numbers. The results suggest that increasing the wall roughness leads to a reduction in velocity at low Reynolds numbers (R e = 1 $Re = 1$) and an increment at high Reynolds numbers (R e = 10 $Re = 10$). For any Reynolds number, a roughness with an odd multiple of wave number (k = 6 , 10 $k = 6,10$) will result in a more stable velocity profile compared to one with an even multiple of wave number (k = 4 , 8 $k = 4,8$). Decreasing the relaxation time λ ¯ 1 ${\bar{\lambda }}_1$ while increasing the retardation time λ ¯ 2 ${\bar{\lambda }}_2$ and Hartmann number H a $Ha$ can diminish the impact of wall roughness ε $\varepsilon $ and surface charge density σ s ${\sigma }_s$ on volumetric flow rate, independent of the Reynolds number. Interestingly, in the existence of wall roughness, further consideration of the effect of surface charge on slip leads to a 15% drop in volumetric flow rate at R e = 1 $Re = 1$ and a 32% slippage at R e = 10 $Re = 10$ . However, in the condition where the effect of surface charge on slip is considered, further examination of the presence of wall roughness only results in a 1.4% decline in volumetric flow rate at R e = 1 $Re = 1$ and a 1.6% rise at R e = 10 $Re = 10$ . These findings are crucial for optimizing the EMHD flow models in microchannels.
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@article {pmid38809093,
year = {2024},
author = {Li, D and Dong, J and Li, H},
title = {Electromagnetohydrodynamic (EMHD) flow of Jeffrey fluid through a rough circular microchannel with surface charge-dependent slip.},
journal = {Electrophoresis},
volume = {},
number = {},
pages = {},
doi = {10.1002/elps.202300297},
pmid = {38809093},
issn = {1522-2683},
support = {11962021//National Natural Science Foundation of China/ ; 2021MS05020//Natural Science Foundation of Inner Mongolia Autonomous Region/ ; JY20220138//Basic Science Research Fund in the Universities Directly under the Inner Mongolia Autonomous Region/ ; JY20220331//Basic Science Research Fund in the Universities Directly under the Inner Mongolia Autonomous Region/ ; },
abstract = {This research examines the electromagnetohydrodynamic (EMHD) flow of Jeffrey fluid in a rough circular microchannel while considering the effect of surface charge on slip. The channel wall corrugations are described as periodic sinusoidal waves with small amplitudes. The perturbation method is employed to derive solutions for velocity and volumetric flow rate, and a combination of three-dimensional (3D) and two-dimensional (2D) graphical representations is utilized to effectively illustrate the impacts of relevant parameters on them. The significance of the Reynolds number R e $Re$ in investigations of EMHD flow is particularly emphasized. Furthermore, the effect of wall roughness ε $\varepsilon $ and wave number k $k$ on velocity and the influence of wall roughness ε $\varepsilon $ and surface charge density σ s ${\sigma }_
s$ on volumetric flow rate are primarily focused on, respectively, at various Reynolds numbers. The results suggest that increasing the wall roughness leads to a reduction in velocity at low Reynolds numbers (R e = 1 $Re = 1$) and an increment at high Reynolds numbers (R e = 10 $Re = 10$). For any Reynolds number, a roughness with an odd multiple of wave number (k = 6 , 10 $k = 6,10$) will result in a more stable velocity profile compared to one with an even multiple of wave number (k = 4 , 8 $k = 4,8$). Decreasing the relaxation time λ ¯ 1 ${\bar{\lambda }}
_1$ while increasing the retardation time λ ¯ 2 ${\bar{\lambda }}
_2$ and Hartmann number H a $Ha$ can diminish the impact of wall roughness ε $\varepsilon $ and surface charge density σ s ${\sigma }_
s$ on volumetric flow rate, independent of the Reynolds number. Interestingly, in the existence of wall roughness, further consideration of the effect of surface charge on slip leads to a 15% drop in volumetric flow rate at R e = 1 $Re = 1$ and a 32% slippage at R e = 10 $Re = 10$ . However, in the condition where the effect of surface charge on slip is considered, further examination of the presence of wall roughness only results in a 1.4% decline in volumetric flow rate at R e = 1 $Re = 1$ and a 1.6% rise at R e = 10 $Re = 10$ . These findings are crucial for optimizing the EMHD flow models in microchannels.},
}
RevDate: 2024-05-25
Experiment study on focusing pattern prediction of particles in asymmetric contraction-expansion array channel.
Electrophoresis [Epub ahead of print].
Contraction-expansion array (CEA) microchannel is a typical structure applied on particle/cell manipulation. The prediction of the particle focusing pattern in CEA microchannel is worthwhile to be investigate deeply. Here, we demonstrated a virtual boundary method by flow field analysis and theoretical derivation. The calculating method of the virtual boundary location, related to the Reynolds number (Re) and the structure parameter RW, was proposed. Combining the approximate Poiseuille flow pattern based on the virtual boundary method with the simulation results of Dean flow, the main line pattern and the main/lateral lines pattern were predicted and validated in experiments. The transformation from the main line pattern to the main/lateral lines pattern can be facilitated by increasing Re, decreasing RW , and decreasing α. An empirical formula was derived to characterize the critical condition of the transformation. The virtual boundary method can provide a guidance for asymmetric CEA channel design and contribute to the widespread application of microfluidic particle focusing.
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@article {pmid38794969,
year = {2024},
author = {Shi, X and He, Q and Tan, W and Lu, Y and Zhu, G},
title = {Experiment study on focusing pattern prediction of particles in asymmetric contraction-expansion array channel.},
journal = {Electrophoresis},
volume = {},
number = {},
pages = {},
doi = {10.1002/elps.202400042},
pmid = {38794969},
issn = {1522-2683},
support = {22078236//National Natural Science Foundation of China/ ; 21JCZDJC00420//Science and Technology Plan Project of Tianjin/ ; },
abstract = {Contraction-expansion array (CEA) microchannel is a typical structure applied on particle/cell manipulation. The prediction of the particle focusing pattern in CEA microchannel is worthwhile to be investigate deeply. Here, we demonstrated a virtual boundary method by flow field analysis and theoretical derivation. The calculating method of the virtual boundary location, related to the Reynolds number (Re) and the structure parameter RW, was proposed. Combining the approximate Poiseuille flow pattern based on the virtual boundary method with the simulation results of Dean flow, the main line pattern and the main/lateral lines pattern were predicted and validated in experiments. The transformation from the main line pattern to the main/lateral lines pattern can be facilitated by increasing Re, decreasing RW , and decreasing α. An empirical formula was derived to characterize the critical condition of the transformation. The virtual boundary method can provide a guidance for asymmetric CEA channel design and contribute to the widespread application of microfluidic particle focusing.},
}
RevDate: 2024-05-24
Enhancing Energy Harvesting Efficiency of Flapping Wings with Leading-Edge Magnus Effect Cylinder.
Biomimetics (Basel, Switzerland), 9(5): pii:biomimetics9050293.
According to the Magnus principle, a rotating cylinder experiences a lateral force perpendicular to the incoming flow direction. This phenomenon can be harnessed to boost the lift of an airfoil by positioning a rotating cylinder at the leading edge. In this study, we simulate flapping-wing motion using the sliding mesh technique in a heaving coordinate system to investigate the energy harvesting capabilities of Magnus effect flapping wings (MEFWs) featuring a leading-edge rotating cylinder. Through analysis of the flow field vortex structure and pressure distribution, we explore how control parameters such as gap width, rotational speed ratio, and phase difference of the leading-edge rotating cylinder impact the energy harvesting characteristics of the flapping wing. The results demonstrate that MEFWs effectively mitigate the formation of leading-edge vortices during wing motion. Consequently, this enhances both lift generation and energy harvesting capability. MEFWs with smaller gap widths are less prone to induce the detachment of leading-edge vortices during motion, ensuring a higher peak lift force and an increase in the energy harvesting efficiency. Moreover, higher rotational speed ratios and phase differences, synchronized with wing motion, can prevent leading-edge vortex generation during wing motion. All three control parameters contribute to enhancing the energy harvesting capability of MEFWs within a certain range. At the examined Reynolds number, the optimal parameter values are determined to be a∗ = 0.0005, R = 3, and ϕ0 = 0°.
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@article {pmid38786503,
year = {2024},
author = {Zhang, H and Zhu, B and Chen, W},
title = {Enhancing Energy Harvesting Efficiency of Flapping Wings with Leading-Edge Magnus Effect Cylinder.},
journal = {Biomimetics (Basel, Switzerland)},
volume = {9},
number = {5},
pages = {},
doi = {10.3390/biomimetics9050293},
pmid = {38786503},
issn = {2313-7673},
support = {51576131//National Natural Science Foundation of China/ ; 91852117//National Natural Science Foundation of China/ ; 23PJD070//Shanghai Pujiang Programme/ ; LAB-2023-07-WD//National Key Laboratory of Marine Engine Science and Technology/ ; },
abstract = {According to the Magnus principle, a rotating cylinder experiences a lateral force perpendicular to the incoming flow direction. This phenomenon can be harnessed to boost the lift of an airfoil by positioning a rotating cylinder at the leading edge. In this study, we simulate flapping-wing motion using the sliding mesh technique in a heaving coordinate system to investigate the energy harvesting capabilities of Magnus effect flapping wings (MEFWs) featuring a leading-edge rotating cylinder. Through analysis of the flow field vortex structure and pressure distribution, we explore how control parameters such as gap width, rotational speed ratio, and phase difference of the leading-edge rotating cylinder impact the energy harvesting characteristics of the flapping wing. The results demonstrate that MEFWs effectively mitigate the formation of leading-edge vortices during wing motion. Consequently, this enhances both lift generation and energy harvesting capability. MEFWs with smaller gap widths are less prone to induce the detachment of leading-edge vortices during motion, ensuring a higher peak lift force and an increase in the energy harvesting efficiency. Moreover, higher rotational speed ratios and phase differences, synchronized with wing motion, can prevent leading-edge vortex generation during wing motion. All three control parameters contribute to enhancing the energy harvesting capability of MEFWs within a certain range. At the examined Reynolds number, the optimal parameter values are determined to be a∗ = 0.0005, R = 3, and ϕ0 = 0°.},
}
RevDate: 2024-05-17
A quasi-realistic computational model development and flow field study of the human upper and central airways.
Medical & biological engineering & computing [Epub ahead of print].
The impact of drug delivery and particulate matter exposure on the human respiratory tract is influenced by various anatomical and physiological factors, particularly the structure of the respiratory tract and its fluid dynamics. This study employs computational fluid dynamics (CFD) to investigate airflow in two 3D models of the human air conducting zone. The first model uses a combination of CT-scan images and geometrical data from human cadaver to extract the upper and central airways down to the ninth generation, while the second model develops the lung airways from the first Carina to the end of the ninth generation using Kitaoka's deterministic algorithm. The study examines the differences in geometrical characteristics, airflow rates, velocity, Reynolds number, and pressure drops of both models in the inhalation and exhalation phases for different lobes and generations of the airways. From trachea to the ninth generation, the average air flowrates and Reynolds numbers exponentially decay in both models during inhalation and exhalation. The steady drop is the case for the average air velocity in Kitaoka's model, while that experiences a maximum in the 3rd or 4th generation in the quasi-realistic model. Besides, it is shown that the flow field remains laminar in the upper and central airways up to the total flow rate of 15 l/min. The results of this work can contribute to the understanding of flow behavior in upper respiratory tract.
Additional Links: PMID-38758518
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@article {pmid38758518,
year = {2024},
author = {Rezazadeh, MR and Dastan, A and Sadrizadeh, S and Abouali, O},
title = {A quasi-realistic computational model development and flow field study of the human upper and central airways.},
journal = {Medical & biological engineering & computing},
volume = {},
number = {},
pages = {},
pmid = {38758518},
issn = {1741-0444},
abstract = {The impact of drug delivery and particulate matter exposure on the human respiratory tract is influenced by various anatomical and physiological factors, particularly the structure of the respiratory tract and its fluid dynamics. This study employs computational fluid dynamics (CFD) to investigate airflow in two 3D models of the human air conducting zone. The first model uses a combination of CT-scan images and geometrical data from human cadaver to extract the upper and central airways down to the ninth generation, while the second model develops the lung airways from the first Carina to the end of the ninth generation using Kitaoka's deterministic algorithm. The study examines the differences in geometrical characteristics, airflow rates, velocity, Reynolds number, and pressure drops of both models in the inhalation and exhalation phases for different lobes and generations of the airways. From trachea to the ninth generation, the average air flowrates and Reynolds numbers exponentially decay in both models during inhalation and exhalation. The steady drop is the case for the average air velocity in Kitaoka's model, while that experiences a maximum in the 3rd or 4th generation in the quasi-realistic model. Besides, it is shown that the flow field remains laminar in the upper and central airways up to the total flow rate of 15 l/min. The results of this work can contribute to the understanding of flow behavior in upper respiratory tract.},
}
RevDate: 2024-05-17
Turbulence hierarchy in foreign exchange markets.
Physical review. E, 109(4-1):044313.
We present a multiscale stochastic analysis of foreign exchange rates using the H-theory formalism, which provides a hierarchical intermittency model for the information cascade in the currency market. We examine the distributions of returns and volatilities for the three most traded currency pairs: euro-U.S. dollar, U.S. dollar-Japanese yen, and British pound-U.S. dollar. We find that these markets have a hierarchy of timescales, with larger markets exhibiting more hierarchy levels. We provide a theoretical framework for understanding why the number of levels in the information cascade increases with market size, in analogy with similar behavior for the energy cascade in turbulence as a function of Reynolds number. We briefly argue that using turbulence-like models for financial markets can also provide valuable insights for developing efficient algorithmic trading strategies.
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@article {pmid38755908,
year = {2024},
author = {Vasconcelos, GL and Ribeiro, LRC and Macêdo, AMS and González, IRR and Ospina, R and Brum, AA},
title = {Turbulence hierarchy in foreign exchange markets.},
journal = {Physical review. E},
volume = {109},
number = {4-1},
pages = {044313},
doi = {10.1103/PhysRevE.109.044313},
pmid = {38755908},
issn = {2470-0053},
abstract = {We present a multiscale stochastic analysis of foreign exchange rates using the H-theory formalism, which provides a hierarchical intermittency model for the information cascade in the currency market. We examine the distributions of returns and volatilities for the three most traded currency pairs: euro-U.S. dollar, U.S. dollar-Japanese yen, and British pound-U.S. dollar. We find that these markets have a hierarchy of timescales, with larger markets exhibiting more hierarchy levels. We provide a theoretical framework for understanding why the number of levels in the information cascade increases with market size, in analogy with similar behavior for the energy cascade in turbulence as a function of Reynolds number. We briefly argue that using turbulence-like models for financial markets can also provide valuable insights for developing efficient algorithmic trading strategies.},
}
RevDate: 2024-05-17
Breaking the symmetry of a wavy channel alters the route to chaotic flow.
Physical review. E, 109(4-2):045103.
We numerically explore the two-dimensional, incompressible, isothermal flow through a wavy channel, with a focus on how the channel geometry affects the routes to chaos at Reynolds numbers between 150 and 1000. We find that (i) the period-doubling route arises in a symmetric channel, (ii) the Ruelle-Takens-Newhouse route arises in an asymmetric channel, and (iii) the type-II intermittency route arises in both asymmetric and semiwavy channels. We also find that the flow through the semiwavy channel evolves from a quasiperiodic torus to an unstable invariant set (chaotic saddle), before eventually settling on a period-1 limit-cycle attractor. This study reveals that laminar channel flow at elevated Reynolds numbers can exhibit a variety of nonlinear dynamics. Specifically, it highlights how breaking the symmetry of a wavy channel can not only influence the critical Reynolds number at which chaos emerges, but also diversify the types of bifurcation encountered en route to chaos itself.
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@article {pmid38755871,
year = {2024},
author = {Doranehgard, MH and Karimi, N and Borazjani, I and Li, LKB},
title = {Breaking the symmetry of a wavy channel alters the route to chaotic flow.},
journal = {Physical review. E},
volume = {109},
number = {4-2},
pages = {045103},
doi = {10.1103/PhysRevE.109.045103},
pmid = {38755871},
issn = {2470-0053},
abstract = {We numerically explore the two-dimensional, incompressible, isothermal flow through a wavy channel, with a focus on how the channel geometry affects the routes to chaos at Reynolds numbers between 150 and 1000. We find that (i) the period-doubling route arises in a symmetric channel, (ii) the Ruelle-Takens-Newhouse route arises in an asymmetric channel, and (iii) the type-II intermittency route arises in both asymmetric and semiwavy channels. We also find that the flow through the semiwavy channel evolves from a quasiperiodic torus to an unstable invariant set (chaotic saddle), before eventually settling on a period-1 limit-cycle attractor. This study reveals that laminar channel flow at elevated Reynolds numbers can exhibit a variety of nonlinear dynamics. Specifically, it highlights how breaking the symmetry of a wavy channel can not only influence the critical Reynolds number at which chaos emerges, but also diversify the types of bifurcation encountered en route to chaos itself.},
}
RevDate: 2024-05-14
AI-based predictive approach via FFB propagation in a driven-cavity of Ostwald de-Waele fluid using CFD-ANN and Levenberg-Marquardt.
Scientific reports, 14(1):11024.
The integration of Artificial Intelligence (AI) and Machine Learning (ML) techniques into computational science has ushered in a new era of innovation and efficiency in various fields, with particular significance in computational fluid dynamics (CFD). Several methods based on AI and Machine Learning (ML) have been standardized in many fields of computational science, including computational fluid dynamics (CFD). This study aims to couple CFD with artificial neural networks (ANNs) to predict the fluid forces that arise when a flowing fluid interacts with obstacles installed in the flow domain. The momentum equation elucidating the flow has been simulated by adopting the finite element method (FEM) for a range of rheological and kinematic conditions. Hydrodynamic forces, including pressure drop between the back and front of the obstacle, surface drag, and lift variations, are measured on the outer surface of the cylinder via CFD simulations. This data has subsequently been fed into a Feed-Forward Back (FFB) propagation neural network for the prediction of such forces with completely unknown data. For all cases, higher predictivity is achieved for the drag coefficient (CD) and lift coefficient (CL) since the mean square error (MSE) is within ± 2% and the coefficient of determination (R) is approximately 99% for all the cases. The influence of pertinent parameters like the power law index (n) and Reynolds number (Re) on velocity, pressure, and drag and lift coefficients is also presented for limited cases. Moreover, a significant reduction in computing time has been noticed while applying hybrid CFD-ANN approach as compared with CFD simulations only.
Additional Links: PMID-38744984
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@article {pmid38744984,
year = {2024},
author = {Refaie Ali, A and Mahmood, R and Asghar, A and Majeed, AH and Behiry, MH},
title = {AI-based predictive approach via FFB propagation in a driven-cavity of Ostwald de-Waele fluid using CFD-ANN and Levenberg-Marquardt.},
journal = {Scientific reports},
volume = {14},
number = {1},
pages = {11024},
pmid = {38744984},
issn = {2045-2322},
abstract = {The integration of Artificial Intelligence (AI) and Machine Learning (ML) techniques into computational science has ushered in a new era of innovation and efficiency in various fields, with particular significance in computational fluid dynamics (CFD). Several methods based on AI and Machine Learning (ML) have been standardized in many fields of computational science, including computational fluid dynamics (CFD). This study aims to couple CFD with artificial neural networks (ANNs) to predict the fluid forces that arise when a flowing fluid interacts with obstacles installed in the flow domain. The momentum equation elucidating the flow has been simulated by adopting the finite element method (FEM) for a range of rheological and kinematic conditions. Hydrodynamic forces, including pressure drop between the back and front of the obstacle, surface drag, and lift variations, are measured on the outer surface of the cylinder via CFD simulations. This data has subsequently been fed into a Feed-Forward Back (FFB) propagation neural network for the prediction of such forces with completely unknown data. For all cases, higher predictivity is achieved for the drag coefficient (CD) and lift coefficient (CL) since the mean square error (MSE) is within ± 2% and the coefficient of determination (R) is approximately 99% for all the cases. The influence of pertinent parameters like the power law index (n) and Reynolds number (Re) on velocity, pressure, and drag and lift coefficients is also presented for limited cases. Moreover, a significant reduction in computing time has been noticed while applying hybrid CFD-ANN approach as compared with CFD simulations only.},
}
RevDate: 2024-05-10
Biologically generated turbulent energy flux in shear flow depends on tensor geometry.
PNAS nexus, 3(2):pgae056 pii:pgae056.
It has been proposed that biologically generated turbulence plays an important role in material transport and ocean mixing. Both experimental and numerical studies have reported evidence of the nonnegligible mixing by moderate Reynolds number swimmers, such as zooplankton, in quiescent water, especially at aggregation scales. However, the interaction between biologically generated agitation and the background flow, as a key factor in biologically generated turbulence that could reshape our previous knowledge of biologically generated turbulence, has long been ignored. Here, we show that the geometry between the biologically generated agitation and the background hydrodynamic shear can determine both the intensity and direction of biologically generated turbulent energy flux. Measuring the migration of a centimeter-scale swimmer-as represented by the brine shrimp Artemia salina-in a shear flow and verifying through an analog experiment with an artificial jet revealed that different geometries between the biologically generated agitation and the background shear can result in spectral energy transferring toward larger or smaller scales, which consequently intensifies or attenuates the large-scale hydrodynamic shear. Our results suggest that the long ignored geometry between the biologically generated agitation and the background flow field is an important factor that should be taken into consideration in future studies of biologically generated turbulence.
Additional Links: PMID-38725533
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@article {pmid38725533,
year = {2024},
author = {Si, X and Fang, L},
title = {Biologically generated turbulent energy flux in shear flow depends on tensor geometry.},
journal = {PNAS nexus},
volume = {3},
number = {2},
pages = {pgae056},
doi = {10.1093/pnasnexus/pgae056},
pmid = {38725533},
issn = {2752-6542},
abstract = {It has been proposed that biologically generated turbulence plays an important role in material transport and ocean mixing. Both experimental and numerical studies have reported evidence of the nonnegligible mixing by moderate Reynolds number swimmers, such as zooplankton, in quiescent water, especially at aggregation scales. However, the interaction between biologically generated agitation and the background flow, as a key factor in biologically generated turbulence that could reshape our previous knowledge of biologically generated turbulence, has long been ignored. Here, we show that the geometry between the biologically generated agitation and the background hydrodynamic shear can determine both the intensity and direction of biologically generated turbulent energy flux. Measuring the migration of a centimeter-scale swimmer-as represented by the brine shrimp Artemia salina-in a shear flow and verifying through an analog experiment with an artificial jet revealed that different geometries between the biologically generated agitation and the background shear can result in spectral energy transferring toward larger or smaller scales, which consequently intensifies or attenuates the large-scale hydrodynamic shear. Our results suggest that the long ignored geometry between the biologically generated agitation and the background flow field is an important factor that should be taken into consideration in future studies of biologically generated turbulence.},
}
RevDate: 2024-05-06
Thermohydraulic analysis of nanofluid flow in tubular heat exchangers with multi-blade turbulators: The adverse effects.
Heliyon, 10(9):e30333.
Based on the significance of heat transfer in tubular flows, various methods of heat transfer enhancement have been developed by scholars. The use of turbulator inserts like twisted tapes is widely discussed and suggested by researchers, and many studies have concentrated on the positive influence of these devices. However, the question is whether these devices always positively impact heat transfer and fluid flow. In this study, efforts were made to find possible adverse impacts of using twisted tapes on the average Nusselt number (Nu), friction factor (f), flow behavior, and performance evaluation criterion (PEC) of water-titania nanofluid. Three-dimensional (3D) numerical methods were used to assess a combination of three different configurations of 156 cases with/without turbulators with different numbers of blades and pitch ratios (PR). Results suggest that at Reynolds number (Re) = 4000, 6000, and 8000, only 25 %, 25 %, and 22.9 % of the examined cases led to PEC values over 1. Based on the results, while twisted tapes raised the Nu by up to 65.1 %, the f can be increased by up to more than six times. Furthermore, streamlines and velocity magnitude contours were employed to discuss the fluid flow behavior in the presence of the turbulators. According to the findings, while with the best turbulator, the PEC value was increased by only 6.3 %, some of the turbulators reduced this parameter by up to 11.8 %, which is more severe. The worst performance was observed with the Case C (three-bladed) turbulator at a PR value of 11, which reduced the PEC by 11.8 %.
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@article {pmid38707334,
year = {2024},
author = {Mohadjer, A and Nobakhti, MH and Nezamabadi, A and Mousavi Ajarostaghi, SS},
title = {Thermohydraulic analysis of nanofluid flow in tubular heat exchangers with multi-blade turbulators: The adverse effects.},
journal = {Heliyon},
volume = {10},
number = {9},
pages = {e30333},
pmid = {38707334},
issn = {2405-8440},
abstract = {Based on the significance of heat transfer in tubular flows, various methods of heat transfer enhancement have been developed by scholars. The use of turbulator inserts like twisted tapes is widely discussed and suggested by researchers, and many studies have concentrated on the positive influence of these devices. However, the question is whether these devices always positively impact heat transfer and fluid flow. In this study, efforts were made to find possible adverse impacts of using twisted tapes on the average Nusselt number (Nu), friction factor (f), flow behavior, and performance evaluation criterion (PEC) of water-titania nanofluid. Three-dimensional (3D) numerical methods were used to assess a combination of three different configurations of 156 cases with/without turbulators with different numbers of blades and pitch ratios (PR). Results suggest that at Reynolds number (Re) = 4000, 6000, and 8000, only 25 %, 25 %, and 22.9 % of the examined cases led to PEC values over 1. Based on the results, while twisted tapes raised the Nu by up to 65.1 %, the f can be increased by up to more than six times. Furthermore, streamlines and velocity magnitude contours were employed to discuss the fluid flow behavior in the presence of the turbulators. According to the findings, while with the best turbulator, the PEC value was increased by only 6.3 %, some of the turbulators reduced this parameter by up to 11.8 %, which is more severe. The worst performance was observed with the Case C (three-bladed) turbulator at a PR value of 11, which reduced the PEC by 11.8 %.},
}
RevDate: 2024-05-03
Enhancement of thermal energy transfer behind a double consecutive expansion utilizing a variable magnetic field.
Scientific reports, 14(1):10236.
This research focuses on utilizing non-uniform magnetic fields, induced by dipoles, to control and enhance thermal energy transfer in a two-dimensional cooling conduit including a double backward-facing step. The presence of electronic equipment along the straight channel path creates such arrangements, and cooling is often ineffective in the corners of the formed steps. The use of a non-constant magnetic field is a passive technique to improve the cooling rate in these sections without changing the internal geometry, thereby increasing the heat transfer rate. A commercial software based on the finite volume technique is employed to solve the governing equations of fluid flow and heat transfer. Multiple parameters are examined in this study, including the flow Reynolds number (12.5-50), dipole location and strength (0.1-5 A-m), and the number of dipoles (single or double). The results indicate that all of these parameters have a significant impact on the thermal energy transfer. The results of the study show that a single dipole increase the average heat transfer by about 22%, two magnetic fields by 40%, the strength of the magnetic source by 24% with respect to the non-magnetic field in the present study.
Additional Links: PMID-38702376
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@article {pmid38702376,
year = {2024},
author = {Bahrami, HR and Ghaedi, M},
title = {Enhancement of thermal energy transfer behind a double consecutive expansion utilizing a variable magnetic field.},
journal = {Scientific reports},
volume = {14},
number = {1},
pages = {10236},
pmid = {38702376},
issn = {2045-2322},
abstract = {This research focuses on utilizing non-uniform magnetic fields, induced by dipoles, to control and enhance thermal energy transfer in a two-dimensional cooling conduit including a double backward-facing step. The presence of electronic equipment along the straight channel path creates such arrangements, and cooling is often ineffective in the corners of the formed steps. The use of a non-constant magnetic field is a passive technique to improve the cooling rate in these sections without changing the internal geometry, thereby increasing the heat transfer rate. A commercial software based on the finite volume technique is employed to solve the governing equations of fluid flow and heat transfer. Multiple parameters are examined in this study, including the flow Reynolds number (12.5-50), dipole location and strength (0.1-5 A-m), and the number of dipoles (single or double). The results indicate that all of these parameters have a significant impact on the thermal energy transfer. The results of the study show that a single dipole increase the average heat transfer by about 22%, two magnetic fields by 40%, the strength of the magnetic source by 24% with respect to the non-magnetic field in the present study.},
}
RevDate: 2024-05-01
A modified drag coefficient model for calculating the terminal settling velocity and horizontal diffusion distance of irregular plume particles in deep-sea mining.
Environmental science and pollution research international [Epub ahead of print].
Deep-sea mining inevitably produces plumes, which will pose a serious threat to the marine environment with the continuous movement and diffusion of plumes along with ocean currents. The terminal settling velocity (wt) of irregular particles is one of the crucial factors for determining the plumes' diffusion range. It is generally calculated by drag coefficient (CD), while most existing CD models only consider single shape characteristic parameter or have a smaller range of Reynolds number (Re). In this study, a new shape factor (γ) of irregular particles is proposed by considering the thickness (one-dimension), the projected area (two-dimension), and the surface area (three-dimension) of irregular particles as well as their coupling effect to establish a modified CD model for calculating the wt. A modified Gaussian plume model is proposed to predict the horizontal diffusion distance of the plume particles by considering the settling velocity and diffusion effect of irregular particles. Research results show that the wt increases nearly linearly, with a gradually decreased slope and slightly then greatly with the increasing of γ, dp (diameter) and ρp (density), respectively. The modified CD model is verified to be more valid with a wider application range (Re < 3×10[5]) than five existing CD models by the test results. The larger the ρp or dp, the larger the wt and thus the smaller the Sh. This study could provide a theoretical basis for calculating the plume diffusion range to further study the impact of deep-sea mining on the ocean environment.
Additional Links: PMID-38691288
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@article {pmid38691288,
year = {2024},
author = {Liu, ZL and Rao, QH and Yi, W and Huang, W},
title = {A modified drag coefficient model for calculating the terminal settling velocity and horizontal diffusion distance of irregular plume particles in deep-sea mining.},
journal = {Environmental science and pollution research international},
volume = {},
number = {},
pages = {},
pmid = {38691288},
issn = {1614-7499},
support = {2021JC0010//Major project of Hunan Natural Science Foundation/ ; 2022zzts0036//Fundamental Research Funds for Central Universities of the Central South University/ ; },
abstract = {Deep-sea mining inevitably produces plumes, which will pose a serious threat to the marine environment with the continuous movement and diffusion of plumes along with ocean currents. The terminal settling velocity (wt) of irregular particles is one of the crucial factors for determining the plumes' diffusion range. It is generally calculated by drag coefficient (CD), while most existing CD models only consider single shape characteristic parameter or have a smaller range of Reynolds number (Re). In this study, a new shape factor (γ) of irregular particles is proposed by considering the thickness (one-dimension), the projected area (two-dimension), and the surface area (three-dimension) of irregular particles as well as their coupling effect to establish a modified CD model for calculating the wt. A modified Gaussian plume model is proposed to predict the horizontal diffusion distance of the plume particles by considering the settling velocity and diffusion effect of irregular particles. Research results show that the wt increases nearly linearly, with a gradually decreased slope and slightly then greatly with the increasing of γ, dp (diameter) and ρp (density), respectively. The modified CD model is verified to be more valid with a wider application range (Re < 3×10[5]) than five existing CD models by the test results. The larger the ρp or dp, the larger the wt and thus the smaller the Sh. This study could provide a theoretical basis for calculating the plume diffusion range to further study the impact of deep-sea mining on the ocean environment.},
}
RevDate: 2024-04-26
Numerical Simulation of the Advantages of the Figure-Eight Flapping Motion of an Insect on Aerodynamics under Low Reynolds Number Conditions.
Biomimetics (Basel, Switzerland), 9(4): pii:biomimetics9040249.
In proceeding with the advanced development of small unmanned aerial vehicles (UAVs), which are small flying machines, understanding the flight of insects is important because UAVs that use flight are attracting attention. The figure-eight trajectory of the wing tips is often observed in the flight of insects. In this study, we investigated the more efficient figure-eight motion patterns in generating lift during the hovering motion and the relationship between figure-eight motion and Reynolds number. For this purpose, we compared the ratios of the cycle-averaged lift coefficient to the power coefficient generated from each motion by varying the elevation motion angle, which is the rotational motion that represents the figure-eight motion, and the Reynolds number. The result showed that the motion with a smaller initial phase of the elevation motion angle (φe0≤90°) could generate lift more efficiently at all Reynolds numbers. In addition, the figure-eight motion was more effective when the Reynolds number was low.
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@article {pmid38667261,
year = {2024},
author = {Yoshida, M and Fukui, T},
title = {Numerical Simulation of the Advantages of the Figure-Eight Flapping Motion of an Insect on Aerodynamics under Low Reynolds Number Conditions.},
journal = {Biomimetics (Basel, Switzerland)},
volume = {9},
number = {4},
pages = {},
doi = {10.3390/biomimetics9040249},
pmid = {38667261},
issn = {2313-7673},
abstract = {In proceeding with the advanced development of small unmanned aerial vehicles (UAVs), which are small flying machines, understanding the flight of insects is important because UAVs that use flight are attracting attention. The figure-eight trajectory of the wing tips is often observed in the flight of insects. In this study, we investigated the more efficient figure-eight motion patterns in generating lift during the hovering motion and the relationship between figure-eight motion and Reynolds number. For this purpose, we compared the ratios of the cycle-averaged lift coefficient to the power coefficient generated from each motion by varying the elevation motion angle, which is the rotational motion that represents the figure-eight motion, and the Reynolds number. The result showed that the motion with a smaller initial phase of the elevation motion angle (φe0≤90°) could generate lift more efficiently at all Reynolds numbers. In addition, the figure-eight motion was more effective when the Reynolds number was low.},
}
RevDate: 2024-04-24
Influence of the internal structure of straight microchannels on inertial transport behavior of particles.
Heliyon, 10(8):e29577.
The rapid advancement of Micro-Electro-Mechanical Systems (MEMS) technology has established microfluidics as a pivotal field. This technology marks the onset of a new era in various applications, including drug testing, cell culture, and disease monitoring, underscoring its extensive practicality and potential for future exploration. This research delves into the intricate behavior of particle inertial migration within microchannels, particularly focusing on the impact of different channel structures and Reynolds numbers (Re). Our studies reveal that particles in microchannels with one-sided sharp-cornered microstructures migrate towards the sharp corner at a relative position of 0.4 under low flow rates, and towards the straight wall side at a relative position of 0.8 under high flow rates. The migration pattern of equilibrium positions varies with different arrangements of sharp-corner structures, achieving stability at the channel's center only when the sharp corners are symmetrically arranged on both sides. Our investigation into the shape of microstructures indicates that sharp-cornered structures generate a more stable secondary flow compared to rectangular and semi-circular structures, preventing particle aggregation at the outlet. To address the challenges associated with handling variable cross-section geometries and solid-wall boundaries in dissipative particle dynamics methods effectively, we have developed a dissipative particle dynamics model specifically for analyzing such microchannels. Building upon our previous research, this model introduces a conservative force coefficient for particles within the microstructured region and an interaction zone that only involves repulsive forces, aligning well with experimental outcomes. Through the study of microstructures' geometric shapes, this paper offers guidance for designing microchannels for particle enrichment. Furthermore, the dissipative particle dynamics model established for the particle flow and solid structure interaction within microstructured channels provides insights into the mesoscale dynamics of liquid-solid two-phase flow and particle motion. In conclusion, this paper aims to enhance particle motion sample preparation techniques, thereby broadening the scope of microfluidic applications in the biomedical field.
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@article {pmid38655341,
year = {2024},
author = {Dong, H and Huang, L and Zhao, L},
title = {Influence of the internal structure of straight microchannels on inertial transport behavior of particles.},
journal = {Heliyon},
volume = {10},
number = {8},
pages = {e29577},
pmid = {38655341},
issn = {2405-8440},
abstract = {The rapid advancement of Micro-Electro-Mechanical Systems (MEMS) technology has established microfluidics as a pivotal field. This technology marks the onset of a new era in various applications, including drug testing, cell culture, and disease monitoring, underscoring its extensive practicality and potential for future exploration. This research delves into the intricate behavior of particle inertial migration within microchannels, particularly focusing on the impact of different channel structures and Reynolds numbers (Re). Our studies reveal that particles in microchannels with one-sided sharp-cornered microstructures migrate towards the sharp corner at a relative position of 0.4 under low flow rates, and towards the straight wall side at a relative position of 0.8 under high flow rates. The migration pattern of equilibrium positions varies with different arrangements of sharp-corner structures, achieving stability at the channel's center only when the sharp corners are symmetrically arranged on both sides. Our investigation into the shape of microstructures indicates that sharp-cornered structures generate a more stable secondary flow compared to rectangular and semi-circular structures, preventing particle aggregation at the outlet. To address the challenges associated with handling variable cross-section geometries and solid-wall boundaries in dissipative particle dynamics methods effectively, we have developed a dissipative particle dynamics model specifically for analyzing such microchannels. Building upon our previous research, this model introduces a conservative force coefficient for particles within the microstructured region and an interaction zone that only involves repulsive forces, aligning well with experimental outcomes. Through the study of microstructures' geometric shapes, this paper offers guidance for designing microchannels for particle enrichment. Furthermore, the dissipative particle dynamics model established for the particle flow and solid structure interaction within microstructured channels provides insights into the mesoscale dynamics of liquid-solid two-phase flow and particle motion. In conclusion, this paper aims to enhance particle motion sample preparation techniques, thereby broadening the scope of microfluidic applications in the biomedical field.},
}
RevDate: 2024-04-23
Development of stochastically reconstructed 3D porous media micromodels using additive manufacturing: numerical and experimental validation.
Scientific reports, 14(1):9375.
We propose an integrated methodology for the design and fabrication of 3D micromodels that are suitable for the pore-scale study of transport processes in macroporous materials. The micromodels, that bear the pore-scale characteristics of sandstone, such as porosity, mean pore size, etc, are designed following a stochastic reconstruction algorithm that allows for fine-tuning the porosity and the correlation length of the spatial distribution of the solid material. We then construct a series of 3D micromodels at very fine resolution (i.e. 16 μ m) using a state-of-the-art 3D printing infrastructure, specifically a ProJet MJP3600 3D printer, that utilizes the Material Jetting technology. Within the technical constraints of the 3D printer resolution, the fabricated micromodels represent scaled-up replicas of natural sandstones, that are suitable for the study of the scaling between the permeability, the porosity and the mean pore size. The REV- and pore-scale characteristics of the resulting physical micromodels are recovered using a combination of X-ray micro-CT and microfluidic studies. The experimental results are then compared with single-phase flow simulations at pore-scale and geostatistic models in order to determine the effects of the design parameters on the intrinsic permeability and the spatial correlation of the velocity profile. Our numerical and experimental measurements reveal an excellent match between the properties of the designed and fabricated 3D domains, thus demonstrating the robustness of the proposed methodology for the construction of 3D micromodels with fine-tuned and well-controlled pore-scale characteristics. Furthermore, a pore-scale numerical study over a wider range of 3D digital domain realizations reveals a very good match of the measured permeabilities with the predictions of the Kozeny-Carman formulation based on a single control parameter, k 0 , that is found to have a practically constant value for porosities ϕ ≥ 0.2 . This, in turn, enables us to customize the sample size to meet REV constraints, including enlarging pore morphology while considering the Reynolds number. It is also found that at lower porosities there is a significant increase in the fraction of the non-percolating pores, thus leading to different k 0 , as the porosity approaches a numerically determined critical porosity value, ϕ c , where the domain is no longer percolating.
Additional Links: PMID-38654100
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@article {pmid38654100,
year = {2024},
author = {Lee, D and Ruf, M and Karadimitriou, N and Steeb, H and Manousidaki, M and Varouchakis, EA and Tzortzakis, S and Yiotis, A},
title = {Development of stochastically reconstructed 3D porous media micromodels using additive manufacturing: numerical and experimental validation.},
journal = {Scientific reports},
volume = {14},
number = {1},
pages = {9375},
pmid = {38654100},
issn = {2045-2322},
support = {SFB1313-327154368//Deutsche Forschungsgemeinschaft/ ; 3DmicroPores//Hellenic Foundation for Research and Innovation/ ; },
abstract = {We propose an integrated methodology for the design and fabrication of 3D micromodels that are suitable for the pore-scale study of transport processes in macroporous materials. The micromodels, that bear the pore-scale characteristics of sandstone, such as porosity, mean pore size, etc, are designed following a stochastic reconstruction algorithm that allows for fine-tuning the porosity and the correlation length of the spatial distribution of the solid material. We then construct a series of 3D micromodels at very fine resolution (i.e. 16 μ m) using a state-of-the-art 3D printing infrastructure, specifically a ProJet MJP3600 3D printer, that utilizes the Material Jetting technology. Within the technical constraints of the 3D printer resolution, the fabricated micromodels represent scaled-up replicas of natural sandstones, that are suitable for the study of the scaling between the permeability, the porosity and the mean pore size. The REV- and pore-scale characteristics of the resulting physical micromodels are recovered using a combination of X-ray micro-CT and microfluidic studies. The experimental results are then compared with single-phase flow simulations at pore-scale and geostatistic models in order to determine the effects of the design parameters on the intrinsic permeability and the spatial correlation of the velocity profile. Our numerical and experimental measurements reveal an excellent match between the properties of the designed and fabricated 3D domains, thus demonstrating the robustness of the proposed methodology for the construction of 3D micromodels with fine-tuned and well-controlled pore-scale characteristics. Furthermore, a pore-scale numerical study over a wider range of 3D digital domain realizations reveals a very good match of the measured permeabilities with the predictions of the Kozeny-Carman formulation based on a single control parameter, k 0 , that is found to have a practically constant value for porosities ϕ ≥ 0.2 . This, in turn, enables us to customize the sample size to meet REV constraints, including enlarging pore morphology while considering the Reynolds number. It is also found that at lower porosities there is a significant increase in the fraction of the non-percolating pores, thus leading to different k 0 , as the porosity approaches a numerically determined critical porosity value, ϕ c , where the domain is no longer percolating.},
}
RevDate: 2024-04-22
The influence of needleless connectors and inserted catheters on flow rates through vascular introducer sheaths.
Anaesthesia and intensive care [Epub ahead of print].
SummaryA vascular introducer sheath is often used for rapid volume replacement. However, common manipulations such as the addition of needleless connectors to infusion ports and the insertion of catheters or other devices through the introducer sheath may impede flow. In this study we utilised a rapid infuser to deliver room-temperature normal saline through two introducer sheath configurations with and without the addition of needleless connectors and the placement of catheters through the introducer sheaths. The maximal flow rate delivered by the rapid infuser was 1000 mL/min, which was observed with both introducer sheath sizes tested without additional resistive elements. However, with the addition of a needleless connector, flow rates through the introducer sheaths were substantially lower (64 (standard deviation (SD) 6) mL/min and 61 (SD 7) mL/min for the 8.5 Fr and 9 Fr introducers, respectively). Flow rates were also reduced when catheters were placed within the sheaths (298 (SD 9) mL/min with the 7 Fr catheter and 74 (SD 9) mL/min with the 8 Fr catheter placed in an 8.5 Fr sheath; 649 (SD 6) mL/min with the 7 Fr catheter and 356 (SD 14) mL/min with the 8 Fr catheter placed in the 9 Fr sheath). These findings indicated that both needleless connectors and the placement of catheters through vascular introducer sheaths substantially reduced potential flow rates. Even 'large' vascular introducer sheaths capable of delivering high flow rates could be rendered minimally effective for rapid fluid administration when used in this way. Clinicians should consider these impediments to flow when rapid fluid administration is required, and obtain alternative vascular access if necessary.
Additional Links: PMID-38649298
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@article {pmid38649298,
year = {2024},
author = {Smeltz, AM and Patel, DS and Williams, JH},
title = {The influence of needleless connectors and inserted catheters on flow rates through vascular introducer sheaths.},
journal = {Anaesthesia and intensive care},
volume = {},
number = {},
pages = {310057X241226715},
doi = {10.1177/0310057X241226715},
pmid = {38649298},
issn = {0310-057X},
abstract = {SummaryA vascular introducer sheath is often used for rapid volume replacement. However, common manipulations such as the addition of needleless connectors to infusion ports and the insertion of catheters or other devices through the introducer sheath may impede flow. In this study we utilised a rapid infuser to deliver room-temperature normal saline through two introducer sheath configurations with and without the addition of needleless connectors and the placement of catheters through the introducer sheaths. The maximal flow rate delivered by the rapid infuser was 1000 mL/min, which was observed with both introducer sheath sizes tested without additional resistive elements. However, with the addition of a needleless connector, flow rates through the introducer sheaths were substantially lower (64 (standard deviation (SD) 6) mL/min and 61 (SD 7) mL/min for the 8.5 Fr and 9 Fr introducers, respectively). Flow rates were also reduced when catheters were placed within the sheaths (298 (SD 9) mL/min with the 7 Fr catheter and 74 (SD 9) mL/min with the 8 Fr catheter placed in an 8.5 Fr sheath; 649 (SD 6) mL/min with the 7 Fr catheter and 356 (SD 14) mL/min with the 8 Fr catheter placed in the 9 Fr sheath). These findings indicated that both needleless connectors and the placement of catheters through vascular introducer sheaths substantially reduced potential flow rates. Even 'large' vascular introducer sheaths capable of delivering high flow rates could be rendered minimally effective for rapid fluid administration when used in this way. Clinicians should consider these impediments to flow when rapid fluid administration is required, and obtain alternative vascular access if necessary.},
}
RevDate: 2024-04-18
Performance evaluation of nanofluid-based photovoltaic thermal (PVT) system with regression analysis.
Heliyon, 10(7):e29252.
The recent global energy crisis has shocked Bangladesh's power sectors, and experts recommend using alternative energy sources to conserve natural gas, fossil fuels, and electricity. Numerous investigations on the photovoltaic thermal (PVT) system have been carried out to get the source efficiently. As a result, a parametric evaluation of the PVT system's efficiency in Dhaka, Bangladesh, is investigated numerically using CNT nanofluid as a coolant. The numerical simulation is performed using the Galerkin weighted residual based finite element method. For accurate computations, the meteorological data for Dhaka, Bangladesh, is taken from open sources of Renewables.ninja. The effect of regulating parameters Reynolds number (200 ≤ Re ≤ 1000), solar irradiation (200 W/m[2] ≤ G ≤ 1000 W/m[2]), and the monthly influence on performance such as cell temperature, fluid domain exit temperature, efficiencies, and energy are discussed. In addition, regression analyses of electrical efficiency and thermal efficiency are discussed for the input variables Reynolds number and solar irradiation. After postprocessing, empirical results are compiled and presented as 3D surface graphs, tables, and line diagrams. As the Reynolds number increased, the cell temperature and discharge temperature decreased, resulting in increased efficiency. However, the opposite situation is found for solar irradiation. Month-to-month variation also has a considerable impact on photovoltaic thermal performance. This research will help to improve the efficacy of PVTs in Dhaka, Bangladesh, by identifying useful alternative renewable energy sources.
Additional Links: PMID-38633639
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@article {pmid38633639,
year = {2024},
author = {Azad, AK and Parvin, S and Hossain, T},
title = {Performance evaluation of nanofluid-based photovoltaic thermal (PVT) system with regression analysis.},
journal = {Heliyon},
volume = {10},
number = {7},
pages = {e29252},
pmid = {38633639},
issn = {2405-8440},
abstract = {The recent global energy crisis has shocked Bangladesh's power sectors, and experts recommend using alternative energy sources to conserve natural gas, fossil fuels, and electricity. Numerous investigations on the photovoltaic thermal (PVT) system have been carried out to get the source efficiently. As a result, a parametric evaluation of the PVT system's efficiency in Dhaka, Bangladesh, is investigated numerically using CNT nanofluid as a coolant. The numerical simulation is performed using the Galerkin weighted residual based finite element method. For accurate computations, the meteorological data for Dhaka, Bangladesh, is taken from open sources of Renewables.ninja. The effect of regulating parameters Reynolds number (200 ≤ Re ≤ 1000), solar irradiation (200 W/m[2] ≤ G ≤ 1000 W/m[2]), and the monthly influence on performance such as cell temperature, fluid domain exit temperature, efficiencies, and energy are discussed. In addition, regression analyses of electrical efficiency and thermal efficiency are discussed for the input variables Reynolds number and solar irradiation. After postprocessing, empirical results are compiled and presented as 3D surface graphs, tables, and line diagrams. As the Reynolds number increased, the cell temperature and discharge temperature decreased, resulting in increased efficiency. However, the opposite situation is found for solar irradiation. Month-to-month variation also has a considerable impact on photovoltaic thermal performance. This research will help to improve the efficacy of PVTs in Dhaka, Bangladesh, by identifying useful alternative renewable energy sources.},
}
RevDate: 2024-04-16
From an obliquely falling rod in a viscous fluid to the motion of suspended magnetic bead chains that are driven by a gradient magnetic field and that make an arbitrary angle with the magnetic force vector: A Stokes flow study.
PloS one, 19(4):e0301852 pii:PONE-D-24-01635.
In view of the growing role of magnetic particles under magnetic field influence in medical and other applications, and perforce the bead chaining, it is important to understand more generally the chain dynamics. As is well known, in the presence of a magnetic field, magnetic beads tend to form chains that are aligned with the magnetic field vector. In addition, if there is a magnetic field gradient, there will be a magnetic force acting on this chain. The main goal of the present research is to study the motion of a magnetic bead chain that makes an arbitrary angle with the magnetic force vector in the Stokes flow limit, that is, in the limit of zero Reynolds number. We used the public-domain computer program HYDRO++ to calculate the mobility matrix, which relates the magnetic force acting on the chain to the velocity of the chain, for a chain of N beads making an arbitrary angle with the magnetic force vector. Because of the presence of off-diagonal elements of the mobility matrix, as the chain is drawn in the direction of the magnetic force, it is also deflected to the side. We derived analytic solutions for this motion. Also, for bead chains moving in directions both parallel and perpendicular to their lengths, we fit three-parameter functions to solutions from HYDRO++. We found the fits to be excellent. Combining these results with the analytic solutions, we obtained expressions for the velocity components for the bead chains that provide excellent fits to HYDRO++ solutions for arbitrary angles. Finally, we apply the methodology used for the bead chain studies to the study of an obliquely falling rod in a viscous fluid and derive analytic solutions for the velocity components of the obliquely falling rod.
Additional Links: PMID-38625980
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@article {pmid38625980,
year = {2024},
author = {Deissler, RJ and Al Helo, R and Brown, R},
title = {From an obliquely falling rod in a viscous fluid to the motion of suspended magnetic bead chains that are driven by a gradient magnetic field and that make an arbitrary angle with the magnetic force vector: A Stokes flow study.},
journal = {PloS one},
volume = {19},
number = {4},
pages = {e0301852},
doi = {10.1371/journal.pone.0301852},
pmid = {38625980},
issn = {1932-6203},
abstract = {In view of the growing role of magnetic particles under magnetic field influence in medical and other applications, and perforce the bead chaining, it is important to understand more generally the chain dynamics. As is well known, in the presence of a magnetic field, magnetic beads tend to form chains that are aligned with the magnetic field vector. In addition, if there is a magnetic field gradient, there will be a magnetic force acting on this chain. The main goal of the present research is to study the motion of a magnetic bead chain that makes an arbitrary angle with the magnetic force vector in the Stokes flow limit, that is, in the limit of zero Reynolds number. We used the public-domain computer program HYDRO++ to calculate the mobility matrix, which relates the magnetic force acting on the chain to the velocity of the chain, for a chain of N beads making an arbitrary angle with the magnetic force vector. Because of the presence of off-diagonal elements of the mobility matrix, as the chain is drawn in the direction of the magnetic force, it is also deflected to the side. We derived analytic solutions for this motion. Also, for bead chains moving in directions both parallel and perpendicular to their lengths, we fit three-parameter functions to solutions from HYDRO++. We found the fits to be excellent. Combining these results with the analytic solutions, we obtained expressions for the velocity components for the bead chains that provide excellent fits to HYDRO++ solutions for arbitrary angles. Finally, we apply the methodology used for the bead chain studies to the study of an obliquely falling rod in a viscous fluid and derive analytic solutions for the velocity components of the obliquely falling rod.},
}
RevDate: 2024-04-15
Thermal-hydraulic performance and flow phenomenon evaluation of a curved trapezoidal corrugated channel with E-shaped baffles implementing hybrid nanofluid.
Heliyon, 10(7):e28698.
A numerical investigation of a curved trapezoidal-corrugated channel with E-shaped baffles is conducted for thermal-hydraulic performance and flow behavior involving the use of single and hybrid nanofluids. This investigation introduces a unique integrated methodology for enhancing heat transfer efficiency by simultaneously combining geometric modifications and optimizing coolant utilization. To simulate turbulent, single-phase flow in three-dimensional corrugated channels, a computational model has been developed. The model considers a Reynolds number (Re) range of 5 × 10[3]≤Re ≤ 35 × 10[3] and implies a uniform heat flux of 1000 W/m[2]. A commercial software, Ansys fluent was used in order to simulate the fluid flow by setting the inlet temperature at 300 K and velocity according to the Reynolds number. The continuity equation, momentum equation, and energy equations are discretized using a second-order upwind method. The equation's residual has been assigned a value of 1 × 10[6] for absolute criteria. The study evaluates the thermal-hydraulic performance of single nanofluids (Al2O3/water, CuO/water, SiO2/water) and hybrid nanofluids (Al2O3-Cu/water, TiO2-SiO2/EG-water) at varying volume fractions (1%≤φ ≤ 5%). Additionally, the investigation examines the effects of corrugations, baffles, and geometric parameter: blockage ratio (BR = 0.10, 0.15, 0.25). The findings demonstrate that the effects of baffles and corrugations can lead to the creation of vortex flow and greater turbulence, which can promote heat transfer enhancement. Various nanofluids demonstrated a significant rise in the Nusselt number, ranging from 35% to 60%, when compared to water in a curved corrugated channel. Additionally, a lower BR resulted in a smaller but still notable gain of 15%-19%. An effective heat exchanger that results in a significant energy dissipation is measured by the energy ratio (ER). The use of corrugated channels with narrow baffles has been found to consistently outperform smooth channels in terms of thermo-hydraulic parameters, leading to enhanced heat transfer. Using BR = 0.10 over 0.25 resulted in an increase in ΔP, HTC, and ER of 48.44%, 18.71%, and 45.86%, respectively. The implementation of a hybrid nanofluid consisting of 1% (20% TiO2-80% SiO2)/(60% Water-40% EG) volume fraction in a curved corrugated channel with baffles resulted in a significant improvement of 36.49% in thermal performance. This finding suggests that the aforementioned nanofluid composition and design parameter, characterized by a blockage ratio of 0.10, are the most effective in enhancing thermal performance.
Additional Links: PMID-38617919
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@article {pmid38617919,
year = {2024},
author = {Ahamed, R and Salehin, M and Ehsan, MM},
title = {Thermal-hydraulic performance and flow phenomenon evaluation of a curved trapezoidal corrugated channel with E-shaped baffles implementing hybrid nanofluid.},
journal = {Heliyon},
volume = {10},
number = {7},
pages = {e28698},
pmid = {38617919},
issn = {2405-8440},
abstract = {A numerical investigation of a curved trapezoidal-corrugated channel with E-shaped baffles is conducted for thermal-hydraulic performance and flow behavior involving the use of single and hybrid nanofluids. This investigation introduces a unique integrated methodology for enhancing heat transfer efficiency by simultaneously combining geometric modifications and optimizing coolant utilization. To simulate turbulent, single-phase flow in three-dimensional corrugated channels, a computational model has been developed. The model considers a Reynolds number (Re) range of 5 × 10[3]≤Re ≤ 35 × 10[3] and implies a uniform heat flux of 1000 W/m[2]. A commercial software, Ansys fluent was used in order to simulate the fluid flow by setting the inlet temperature at 300 K and velocity according to the Reynolds number. The continuity equation, momentum equation, and energy equations are discretized using a second-order upwind method. The equation's residual has been assigned a value of 1 × 10[6] for absolute criteria. The study evaluates the thermal-hydraulic performance of single nanofluids (Al2O3/water, CuO/water, SiO2/water) and hybrid nanofluids (Al2O3-Cu/water, TiO2-SiO2/EG-water) at varying volume fractions (1%≤φ ≤ 5%). Additionally, the investigation examines the effects of corrugations, baffles, and geometric parameter: blockage ratio (BR = 0.10, 0.15, 0.25). The findings demonstrate that the effects of baffles and corrugations can lead to the creation of vortex flow and greater turbulence, which can promote heat transfer enhancement. Various nanofluids demonstrated a significant rise in the Nusselt number, ranging from 35% to 60%, when compared to water in a curved corrugated channel. Additionally, a lower BR resulted in a smaller but still notable gain of 15%-19%. An effective heat exchanger that results in a significant energy dissipation is measured by the energy ratio (ER). The use of corrugated channels with narrow baffles has been found to consistently outperform smooth channels in terms of thermo-hydraulic parameters, leading to enhanced heat transfer. Using BR = 0.10 over 0.25 resulted in an increase in ΔP, HTC, and ER of 48.44%, 18.71%, and 45.86%, respectively. The implementation of a hybrid nanofluid consisting of 1% (20% TiO2-80% SiO2)/(60% Water-40% EG) volume fraction in a curved corrugated channel with baffles resulted in a significant improvement of 36.49% in thermal performance. This finding suggests that the aforementioned nanofluid composition and design parameter, characterized by a blockage ratio of 0.10, are the most effective in enhancing thermal performance.},
}
RevDate: 2024-04-15
Modified Reacting Solver: A Simplified Approach for Capturing the Molecular and Flow Diffusivities for the Nonpremixed MILD Flames.
ACS omega, 9(14):15804-15817.
The present study investigates the applicability of the inlet boundary species Lewis number (combined effect of molecular and flow diffusion) for the nonpremixed moderate and intense low oxygen dilution (MILD) flames. A modified reactive solver named modifiedReactingFoam is developed by including the enthalpy flux in the energy equation and using modified model constants in OpenFOAM. The present solver is tested on the delft-jet-in-hot-coflow burner operating under a moderate and intense low oxygen dilution combustion environment. Along with the flame with Reynolds number 4100, eight other jet-in-hot-coflow flames are simulated to test the capability of the present proposed solver. The main aim of the current work is to investigate the efficacy of the proposed solver in predicting the velocity field, temperatures, and flame lift-off height for the considered flames with a significant reduction in computational time. The predictions with the modified eddy dissipation concept model are improved. However, a significant deviation is still observed in the downstream direction of the burner. The numerical simulations are performed with methane Lewis numbers of 0.9-1.14 by keeping the respective constant Lewis numbers for the inlet boundary species. The modifiedReactingFoam predictions at a methane Lewis number of 1.12 are in very close agreement with the experimental results. The maximum deviation in lift-off heights is within ±3% of the experimental results. The present modified solver outperformed the other combustion models in the literature and reduced the computational time up to 10 times with a combination of DLBFoam compared to the inbuilt solver.
Additional Links: PMID-38617679
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@article {pmid38617679,
year = {2024},
author = {Srinivasarao, M and Lee, BJ and Reddy, VM},
title = {Modified Reacting Solver: A Simplified Approach for Capturing the Molecular and Flow Diffusivities for the Nonpremixed MILD Flames.},
journal = {ACS omega},
volume = {9},
number = {14},
pages = {15804-15817},
pmid = {38617679},
issn = {2470-1343},
abstract = {The present study investigates the applicability of the inlet boundary species Lewis number (combined effect of molecular and flow diffusion) for the nonpremixed moderate and intense low oxygen dilution (MILD) flames. A modified reactive solver named modifiedReactingFoam is developed by including the enthalpy flux in the energy equation and using modified model constants in OpenFOAM. The present solver is tested on the delft-jet-in-hot-coflow burner operating under a moderate and intense low oxygen dilution combustion environment. Along with the flame with Reynolds number 4100, eight other jet-in-hot-coflow flames are simulated to test the capability of the present proposed solver. The main aim of the current work is to investigate the efficacy of the proposed solver in predicting the velocity field, temperatures, and flame lift-off height for the considered flames with a significant reduction in computational time. The predictions with the modified eddy dissipation concept model are improved. However, a significant deviation is still observed in the downstream direction of the burner. The numerical simulations are performed with methane Lewis numbers of 0.9-1.14 by keeping the respective constant Lewis numbers for the inlet boundary species. The modifiedReactingFoam predictions at a methane Lewis number of 1.12 are in very close agreement with the experimental results. The maximum deviation in lift-off heights is within ±3% of the experimental results. The present modified solver outperformed the other combustion models in the literature and reduced the computational time up to 10 times with a combination of DLBFoam compared to the inbuilt solver.},
}
RevDate: 2024-04-15
Inertial migration of aerosol particles in three-dimensional microfluidic channels.
Particuology, 55:23-34.
In recent years, manipulation of particles by inertial microfluidics has attracted significant attention. However, most studies focused on inertial focusing of particles suspended within liquid phase, in which the ratio of the density of the particle to that of the medium is O(1). The investigation on manipulation of aerosol particles in an inertial microfluidics is very limited. In this study, we numerically investigate the aerosol particle's motion in a 3D straight microchannel with rectangular cross section by fully resolved simulation of the particle-air flow. The air flow is modeled by the Navier-Stokes equations. The particle's motions, including translation and rotation, are governed, respectively, by the Newton's second law and the Euler equations without using any approximation models for the lift and drag forces. The coupled mathematical model is numerically solved by combining immersed boundary with lattice Boltzmann method (IB-LBM). We find that the Reynolds number (Re), the particle's initial position, particle's density and diameter are the influential parameters in this process. The equilibrium positions and their stabilities of aerosols are different from those suspended in liquid.
Additional Links: PMID-38620251
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@article {pmid38620251,
year = {2021},
author = {Qian, S and Jiang, M and Liu, Z},
title = {Inertial migration of aerosol particles in three-dimensional microfluidic channels.},
journal = {Particuology},
volume = {55},
number = {},
pages = {23-34},
doi = {10.1016/j.partic.2020.08.001},
pmid = {38620251},
issn = {2210-4291},
abstract = {In recent years, manipulation of particles by inertial microfluidics has attracted significant attention. However, most studies focused on inertial focusing of particles suspended within liquid phase, in which the ratio of the density of the particle to that of the medium is O(1). The investigation on manipulation of aerosol particles in an inertial microfluidics is very limited. In this study, we numerically investigate the aerosol particle's motion in a 3D straight microchannel with rectangular cross section by fully resolved simulation of the particle-air flow. The air flow is modeled by the Navier-Stokes equations. The particle's motions, including translation and rotation, are governed, respectively, by the Newton's second law and the Euler equations without using any approximation models for the lift and drag forces. The coupled mathematical model is numerically solved by combining immersed boundary with lattice Boltzmann method (IB-LBM). We find that the Reynolds number (Re), the particle's initial position, particle's density and diameter are the influential parameters in this process. The equilibrium positions and their stabilities of aerosols are different from those suspended in liquid.},
}
RevDate: 2024-04-13
A Novel Experimental Apparatus for Characterizing Flow Regime in Mechanically Stirred Tanks through Force Sensors.
Sensors (Basel, Switzerland), 24(7): pii:s24072319.
Pressure fluctuations in a mixing tank can provide valuable information about the existing flow regime within the tank, which in turn influences the degree of mixing that can be achieved. In the present work, we propose a prototype for identifying the flow regime in mechanically stirred tanks equipped with four vertical baffles through the characterization of pressure fluctuations. Our innovative proposal is based on force sensors strategically placed in the baffles of the mixing tank. The signals coming from the sensors are transmitted to an electronic module based on an Arduino UNO development board. In the electronic module, the pressure signals are conditioned, amplified and sent via Bluetooth to a computer. In the computer, the signals can be plotted or stored in an Excel file. In addition, the proposed system includes a moving average filtering and a hierarchical bottom-up clustering analysis that can determine the real-time flow regime (i.e., the Reynolds number, Re) in which the tank was operated during the mixing process. Finally, to demonstrate the versatility of the proposed prototype, experiments were conducted to identify the Reynolds number for different flow regimes (static, laminar, transition and turbulent), i.e., 0≤Re≤ 42,955. Obtained results were in agreement with the prevailing consensus on the onset and developed from different flow regimes in mechanically stirred tanks.
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@article {pmid38610530,
year = {2024},
author = {Magos-Rivera, M and Avilés-Cruz, C and Ramírez-Muñoz, J},
title = {A Novel Experimental Apparatus for Characterizing Flow Regime in Mechanically Stirred Tanks through Force Sensors.},
journal = {Sensors (Basel, Switzerland)},
volume = {24},
number = {7},
pages = {},
doi = {10.3390/s24072319},
pmid = {38610530},
issn = {1424-8220},
abstract = {Pressure fluctuations in a mixing tank can provide valuable information about the existing flow regime within the tank, which in turn influences the degree of mixing that can be achieved. In the present work, we propose a prototype for identifying the flow regime in mechanically stirred tanks equipped with four vertical baffles through the characterization of pressure fluctuations. Our innovative proposal is based on force sensors strategically placed in the baffles of the mixing tank. The signals coming from the sensors are transmitted to an electronic module based on an Arduino UNO development board. In the electronic module, the pressure signals are conditioned, amplified and sent via Bluetooth to a computer. In the computer, the signals can be plotted or stored in an Excel file. In addition, the proposed system includes a moving average filtering and a hierarchical bottom-up clustering analysis that can determine the real-time flow regime (i.e., the Reynolds number, Re) in which the tank was operated during the mixing process. Finally, to demonstrate the versatility of the proposed prototype, experiments were conducted to identify the Reynolds number for different flow regimes (static, laminar, transition and turbulent), i.e., 0≤Re≤ 42,955. Obtained results were in agreement with the prevailing consensus on the onset and developed from different flow regimes in mechanically stirred tanks.},
}
RevDate: 2024-04-08
Application of a hydrophobic coating to a pressurized pipe and its effect on energy losses and fluid flow profile.
Scientific reports, 14(1):8236.
The use of additives, generally called DRAs (Drag Reducing Additives), has been proposed to re-duce the energy consumption in pressurized pipes. Although many research works have been conducted to analyze the effect of these additives, less attention have been devoted to the application of coatings to the pipe wall. This paper demonstrates that the application of a hydrophobic coating to the pipe can lead to a head loss reduction for a transition flow regime with moderate Reynolds number values (Re). For this purpose, an experiment was conducted to compare the performance of both coated and uncoated pipes by measuring the head losses and assessing the Drag Reduction Percentage (%DR) and the pipe friction factor (f). This was done for two Polyvinylchloride (PVC) pipes with different nominal diameters (PVC90 and PVC63). In addition, the flow velocity distribution was also measured in all these tests. The %DR decreased as the Re values increased, with the reduction being notably less pronounced for higher Re values. This could be explained by the fact that a partial slip condition is induced by the hydrophobic product. Its effect is significant for a transition regime where the effect of viscosity is important, but it becomes negligible for increasing levels of turbulence. No significant differences were observed in the flow distribution between coated and uncoated pipes, which seems to indicate that the velocity change could be limited to the near-wall viscous sublayer. The results of this work open an important research line aimed at reducing energy costs and the carbon footprint in pipe fluid distribution systems.
Additional Links: PMID-38589633
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@article {pmid38589633,
year = {2024},
author = {Muñóz, AJ and Reca, J and Martínez, J},
title = {Application of a hydrophobic coating to a pressurized pipe and its effect on energy losses and fluid flow profile.},
journal = {Scientific reports},
volume = {14},
number = {1},
pages = {8236},
pmid = {38589633},
issn = {2045-2322},
support = {PID2020-118492RB-C21//Ministerio de Ciencia e Innovación/ ; },
abstract = {The use of additives, generally called DRAs (Drag Reducing Additives), has been proposed to re-duce the energy consumption in pressurized pipes. Although many research works have been conducted to analyze the effect of these additives, less attention have been devoted to the application of coatings to the pipe wall. This paper demonstrates that the application of a hydrophobic coating to the pipe can lead to a head loss reduction for a transition flow regime with moderate Reynolds number values (Re). For this purpose, an experiment was conducted to compare the performance of both coated and uncoated pipes by measuring the head losses and assessing the Drag Reduction Percentage (%DR) and the pipe friction factor (f). This was done for two Polyvinylchloride (PVC) pipes with different nominal diameters (PVC90 and PVC63). In addition, the flow velocity distribution was also measured in all these tests. The %DR decreased as the Re values increased, with the reduction being notably less pronounced for higher Re values. This could be explained by the fact that a partial slip condition is induced by the hydrophobic product. Its effect is significant for a transition regime where the effect of viscosity is important, but it becomes negligible for increasing levels of turbulence. No significant differences were observed in the flow distribution between coated and uncoated pipes, which seems to indicate that the velocity change could be limited to the near-wall viscous sublayer. The results of this work open an important research line aimed at reducing energy costs and the carbon footprint in pipe fluid distribution systems.},
}
RevDate: 2024-04-08
A Scalable Microfluidic Platform for Nanoparticle Formulation: For Exploratory- and Industrial-Level Scales.
Nano letters [Epub ahead of print].
Nanoparticle synthesis on microfluidic platforms provides excellent reproducibility and control over bulk synthesis. While there have been plenty of platforms for producing nanoparticles (NPs) with controlled physicochemical properties, such platforms often operate in a narrow range of predefined flow rates. The flow rate limitation restricts either up-scalability for industrial production or down-scalability for exploratory research use. Here, we present a universal flow rate platform that operates over a wide range of flow rates (0.1-75 mL/min) for small-scale exploratory research and industrial-level synthesis of NPs without compromising the mixing capabilities. The wide range of flow rate is obtained by using a coaxial flow with a triangular microstructure to create a vortex regardless of the flow regime (Reynolds number). The chip synthesizes several types of NPs for gene and protein delivery, including polyplex, lipid NPs, and solid polymer NPs via self-assembly and precipitation, and successfully expresses GFP plasmid DNA in human T cells.
Additional Links: PMID-38588326
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@article {pmid38588326,
year = {2024},
author = {Seder, I and Zheng, T and Zhang, J and Rojas, CC and Helalat, SH and Téllez, RC and Sun, Y},
title = {A Scalable Microfluidic Platform for Nanoparticle Formulation: For Exploratory- and Industrial-Level Scales.},
journal = {Nano letters},
volume = {},
number = {},
pages = {},
doi = {10.1021/acs.nanolett.3c05057},
pmid = {38588326},
issn = {1530-6992},
abstract = {Nanoparticle synthesis on microfluidic platforms provides excellent reproducibility and control over bulk synthesis. While there have been plenty of platforms for producing nanoparticles (NPs) with controlled physicochemical properties, such platforms often operate in a narrow range of predefined flow rates. The flow rate limitation restricts either up-scalability for industrial production or down-scalability for exploratory research use. Here, we present a universal flow rate platform that operates over a wide range of flow rates (0.1-75 mL/min) for small-scale exploratory research and industrial-level synthesis of NPs without compromising the mixing capabilities. The wide range of flow rate is obtained by using a coaxial flow with a triangular microstructure to create a vortex regardless of the flow regime (Reynolds number). The chip synthesizes several types of NPs for gene and protein delivery, including polyplex, lipid NPs, and solid polymer NPs via self-assembly and precipitation, and successfully expresses GFP plasmid DNA in human T cells.},
}
RevDate: 2024-04-05
Dimensionless numbers reveal distinct regimes in the structure and dynamics of pedestrian crowds.
PNAS nexus, 3(4):pgae120.
In fluid mechanics, dimensionless numbers like the Reynolds number help classify flows. We argue that such a classification is also relevant for crowd flows by putting forward the dimensionless Intrusion and Avoidance numbers, which quantify the intrusions into the pedestrians' personal spaces and the imminency of the collisions that they face, respectively. Using an extensive dataset, we show that these numbers delineate regimes where distinct variables characterize the crowd's arrangement, namely, Euclidean distances at low Avoidance number and times-to-collision at low Intrusion number. On the basis of these findings, a perturbative expansion of the individual pedestrian dynamics is carried out around the noninteracting state, in quite general terms. Simulations confirm that this expansion performs well in its expected regime of applicability.
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@article {pmid38577258,
year = {2024},
author = {Cordes, J and Schadschneider, A and Nicolas, A},
title = {Dimensionless numbers reveal distinct regimes in the structure and dynamics of pedestrian crowds.},
journal = {PNAS nexus},
volume = {3},
number = {4},
pages = {pgae120},
pmid = {38577258},
issn = {2752-6542},
abstract = {In fluid mechanics, dimensionless numbers like the Reynolds number help classify flows. We argue that such a classification is also relevant for crowd flows by putting forward the dimensionless Intrusion and Avoidance numbers, which quantify the intrusions into the pedestrians' personal spaces and the imminency of the collisions that they face, respectively. Using an extensive dataset, we show that these numbers delineate regimes where distinct variables characterize the crowd's arrangement, namely, Euclidean distances at low Avoidance number and times-to-collision at low Intrusion number. On the basis of these findings, a perturbative expansion of the individual pedestrian dynamics is carried out around the noninteracting state, in quite general terms. Simulations confirm that this expansion performs well in its expected regime of applicability.},
}
RevDate: 2024-04-01
Efficiency upgrading of solar PVT finned hybrid system in Bangladesh: Flow rate and temperature influences.
Heliyon, 10(7):e28323 pii:S2405-8440(24)04354-8.
This research aims to determine the impact of mass flow rate and inflow temperature on the utility and effectiveness of solar thermal systems using fins with air in various applications in Bangladesh. This study examines a three-dimensional (3D) photovoltaic thermal (PVT) system where we analyze the behavior of a hybrid system with six aluminum sheets (1 mm thick fin as a heat exchange material) inside the heat exchanger where the air takes the direction to pass in waveform through the channels (made of aluminum) using fins. The top side of the fins is bent and affixed to the bottom of the floor of the PV panel to allow heat transfer utilizing the conduction-based method. This study selects inlet fluid mass flow rate and inflow temperature between (0.015-0.535 kg/s), and (10-40 °C) respectively, while comparing the result with experimental/numerical published data based on Bangladesh's weather conditions and applies the finite element method (FEM) to solve heat transfer equations. A brief analysis of the association among Reynolds number with pressure drop and fanning friction factor is included in this paper. Our model can be mounted on building rooftops or open fields where air velocity will be controlled mechanically; thus, it has many applications. This model can be implemented within an agricultural photovoltaic (APV) system, domestic functions, dry agricultural products, and provide heat for greenhouses. The result indicates that 302-514 W thermal energy has been produced for 0.015-0.535 kg/s. For growing inflow temperature, despite the reduction in electrical efficiency, the value of adding electrical and thermal efficiency (overall efficiency) comes with elevation. A 5 °C increase in inflow temperature leads to an overall efficiency increase of 0.33%. This study's findings can help researchers better comprehend air's properties as a heat exchanger in a developed design, and they can be applied to government and commercial projects.
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@article {pmid38560223,
year = {2024},
author = {Tripty, TA and Nasrin, R},
title = {Efficiency upgrading of solar PVT finned hybrid system in Bangladesh: Flow rate and temperature influences.},
journal = {Heliyon},
volume = {10},
number = {7},
pages = {e28323},
doi = {10.1016/j.heliyon.2024.e28323},
pmid = {38560223},
issn = {2405-8440},
abstract = {This research aims to determine the impact of mass flow rate and inflow temperature on the utility and effectiveness of solar thermal systems using fins with air in various applications in Bangladesh. This study examines a three-dimensional (3D) photovoltaic thermal (PVT) system where we analyze the behavior of a hybrid system with six aluminum sheets (1 mm thick fin as a heat exchange material) inside the heat exchanger where the air takes the direction to pass in waveform through the channels (made of aluminum) using fins. The top side of the fins is bent and affixed to the bottom of the floor of the PV panel to allow heat transfer utilizing the conduction-based method. This study selects inlet fluid mass flow rate and inflow temperature between (0.015-0.535 kg/s), and (10-40 °C) respectively, while comparing the result with experimental/numerical published data based on Bangladesh's weather conditions and applies the finite element method (FEM) to solve heat transfer equations. A brief analysis of the association among Reynolds number with pressure drop and fanning friction factor is included in this paper. Our model can be mounted on building rooftops or open fields where air velocity will be controlled mechanically; thus, it has many applications. This model can be implemented within an agricultural photovoltaic (APV) system, domestic functions, dry agricultural products, and provide heat for greenhouses. The result indicates that 302-514 W thermal energy has been produced for 0.015-0.535 kg/s. For growing inflow temperature, despite the reduction in electrical efficiency, the value of adding electrical and thermal efficiency (overall efficiency) comes with elevation. A 5 °C increase in inflow temperature leads to an overall efficiency increase of 0.33%. This study's findings can help researchers better comprehend air's properties as a heat exchanger in a developed design, and they can be applied to government and commercial projects.},
}
RevDate: 2024-03-27
Aerodynamic/Hydrodynamic Investigation of Water Cross-Over for a Bionic Unmanned Aquatic-Aerial Amphibious Vehicle.
Biomimetics (Basel, Switzerland), 9(3): pii:biomimetics9030181.
An aerodynamic/hydrodynamic investigation of water cross-over is performed for a bionic unmanned aquatic-aerial amphibious vehicle (bionic UAAV). According to flying fish features and UAAV flight requirements of water cross-over, the bionic conceptual design of crossing over water is described and planned in multiple stages and modes of motion. A solution procedure for the numerical simulation method, based on a modified SST turbulence model and the VOF model, is expressed, and a verification study is presented using a typical case. Longitudinal-lateral numerical simulation analysis investigates the cruise performance underwater and in the air. The numerical simulation and principal experiment verification are conducted for crossing over water and water surface acceleration. The results indicate that the bionic UAAV has an excellent aerodynamic/hydrodynamic performance and variant configuration to adapt to water cross-over. The bionic UAAV has good water and air navigation stability, and the cruise flying lift-drag ratio is greater than 15 at a low Reynolds number. Its pitching moment has the phenomenon of a "water mound" forming and breaking at the water cross-over process. The present method and the bionic variant configuration provide a feasible water cross-over design and analysis strategy for bionic UAAVs.
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@article {pmid38534866,
year = {2024},
author = {Gan, W and Zuo, Z and Zhuang, J and Bie, D and Xiang, J},
title = {Aerodynamic/Hydrodynamic Investigation of Water Cross-Over for a Bionic Unmanned Aquatic-Aerial Amphibious Vehicle.},
journal = {Biomimetics (Basel, Switzerland)},
volume = {9},
number = {3},
pages = {},
doi = {10.3390/biomimetics9030181},
pmid = {38534866},
issn = {2313-7673},
support = {U2141249, 11902018, and U2141252//National Natural Science Foundation of China/ ; },
abstract = {An aerodynamic/hydrodynamic investigation of water cross-over is performed for a bionic unmanned aquatic-aerial amphibious vehicle (bionic UAAV). According to flying fish features and UAAV flight requirements of water cross-over, the bionic conceptual design of crossing over water is described and planned in multiple stages and modes of motion. A solution procedure for the numerical simulation method, based on a modified SST turbulence model and the VOF model, is expressed, and a verification study is presented using a typical case. Longitudinal-lateral numerical simulation analysis investigates the cruise performance underwater and in the air. The numerical simulation and principal experiment verification are conducted for crossing over water and water surface acceleration. The results indicate that the bionic UAAV has an excellent aerodynamic/hydrodynamic performance and variant configuration to adapt to water cross-over. The bionic UAAV has good water and air navigation stability, and the cruise flying lift-drag ratio is greater than 15 at a low Reynolds number. Its pitching moment has the phenomenon of a "water mound" forming and breaking at the water cross-over process. The present method and the bionic variant configuration provide a feasible water cross-over design and analysis strategy for bionic UAAVs.},
}
RevDate: 2024-03-22
Turbulence Unsteadiness Drives Extreme Clustering.
Physical review letters, 132(10):104005.
We show that the unsteadiness of turbulence has a drastic effect on turbulence parameters and in particle cluster formation. To this end we use direct numerical simulations of particle laden flows with a steady forcing that generates an unsteady large-scale flow. Particle clustering correlates with the instantaneous Taylor-based flow Reynolds number, and anticorrelates with its instantaneous turbulent energy dissipation constant. A dimensional argument for these correlations is presented. In natural flows, unsteadiness can result in extreme particle clustering, which is stronger than the clustering expected from averaged inertial turbulence effects.
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@article {pmid38518328,
year = {2024},
author = {Zapata, F and Angriman, S and Ferran, A and Cobelli, P and Obligado, M and Mininni, PD},
title = {Turbulence Unsteadiness Drives Extreme Clustering.},
journal = {Physical review letters},
volume = {132},
number = {10},
pages = {104005},
doi = {10.1103/PhysRevLett.132.104005},
pmid = {38518328},
issn = {1079-7114},
abstract = {We show that the unsteadiness of turbulence has a drastic effect on turbulence parameters and in particle cluster formation. To this end we use direct numerical simulations of particle laden flows with a steady forcing that generates an unsteady large-scale flow. Particle clustering correlates with the instantaneous Taylor-based flow Reynolds number, and anticorrelates with its instantaneous turbulent energy dissipation constant. A dimensional argument for these correlations is presented. In natural flows, unsteadiness can result in extreme particle clustering, which is stronger than the clustering expected from averaged inertial turbulence effects.},
}
RevDate: 2024-03-22
Spontaneous Stochasticity Amplifies Even Thermal Noise to the Largest Scales of Turbulence in a Few Eddy Turnover Times.
Physical review letters, 132(10):104002.
How predictable are turbulent flows? Here, we use theoretical estimates and shell model simulations to argue that Eulerian spontaneous stochasticity, a manifestation of the nonuniqueness of the solutions to the Euler equation that is conjectured to occur in Navier-Stokes turbulence at high Reynolds numbers, leads to universal statistics at finite times, not just at infinite time as for standard chaos. These universal statistics are predictable, even though individual flow realizations are not. Any small-scale noise vanishing slowly enough with increasing Reynolds number can trigger spontaneous stochasticity, and here we show that thermal noise alone, in the absence of any larger disturbances, would suffice. If confirmed for Navier-Stokes turbulence, our findings would imply that intrinsic stochasticity of turbulent fluid motions at all scales can be triggered even by unavoidable molecular noise, with implications for modeling in engineering, climate, astrophysics, and cosmology.
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@article {pmid38518311,
year = {2024},
author = {Bandak, D and Mailybaev, AA and Eyink, GL and Goldenfeld, N},
title = {Spontaneous Stochasticity Amplifies Even Thermal Noise to the Largest Scales of Turbulence in a Few Eddy Turnover Times.},
journal = {Physical review letters},
volume = {132},
number = {10},
pages = {104002},
doi = {10.1103/PhysRevLett.132.104002},
pmid = {38518311},
issn = {1079-7114},
abstract = {How predictable are turbulent flows? Here, we use theoretical estimates and shell model simulations to argue that Eulerian spontaneous stochasticity, a manifestation of the nonuniqueness of the solutions to the Euler equation that is conjectured to occur in Navier-Stokes turbulence at high Reynolds numbers, leads to universal statistics at finite times, not just at infinite time as for standard chaos. These universal statistics are predictable, even though individual flow realizations are not. Any small-scale noise vanishing slowly enough with increasing Reynolds number can trigger spontaneous stochasticity, and here we show that thermal noise alone, in the absence of any larger disturbances, would suffice. If confirmed for Navier-Stokes turbulence, our findings would imply that intrinsic stochasticity of turbulent fluid motions at all scales can be triggered even by unavoidable molecular noise, with implications for modeling in engineering, climate, astrophysics, and cosmology.},
}
RevDate: 2024-03-22
Correction factors for the drag and pressure flows of power-law fluids through rectangular ducts.
Polymer engineering and science, 63(7):2043-2058.
There are many industrial examples of low Reynolds number non-Newtonian flows through rectangular ducts in polymer processing. They occur in all types of manufacturing processes in which raw polymeric materials are converted into products, ranging from screw extrusion to shaping operations in dies and molds. In addition, they are found in numerous rheological measurement systems. The literature provides various mathematical formulations for non-Newtonian flows through rectangular ducts, but-if not simplified further-their solution usually requires use of numerical techniques. Removing the need for these time-consuming techniques, we present novel analytical correction factors for the drag and pressure flows of power-law fluids in rectangular flow channels. We approximated numerical results for a fully developed flow under isothermal conditions using symbolic regression based on genetic programming. The correction factors can be applied to the analytical theory that describes the flow of power-law fluids between parallel plates to include effects of the side walls in the prediction of flow rate and viscous dissipation.
Additional Links: PMID-38516562
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@article {pmid38516562,
year = {2023},
author = {Marschik, C and Roland, W},
title = {Correction factors for the drag and pressure flows of power-law fluids through rectangular ducts.},
journal = {Polymer engineering and science},
volume = {63},
number = {7},
pages = {2043-2058},
doi = {10.1002/pen.26344},
pmid = {38516562},
issn = {1548-2634},
abstract = {There are many industrial examples of low Reynolds number non-Newtonian flows through rectangular ducts in polymer processing. They occur in all types of manufacturing processes in which raw polymeric materials are converted into products, ranging from screw extrusion to shaping operations in dies and molds. In addition, they are found in numerous rheological measurement systems. The literature provides various mathematical formulations for non-Newtonian flows through rectangular ducts, but-if not simplified further-their solution usually requires use of numerical techniques. Removing the need for these time-consuming techniques, we present novel analytical correction factors for the drag and pressure flows of power-law fluids in rectangular flow channels. We approximated numerical results for a fully developed flow under isothermal conditions using symbolic regression based on genetic programming. The correction factors can be applied to the analytical theory that describes the flow of power-law fluids between parallel plates to include effects of the side walls in the prediction of flow rate and viscous dissipation.},
}
RevDate: 2024-03-21
Instability analysis for MHD boundary layer flow of nanofluid over a rotating disk with anisotropic and isotropic roughness.
Heliyon, 10(6):e26779.
The study focuses on the instability of local linear convective flow in an incompressible boundary layer caused by a rough rotating disk in a steady MHD flow of viscous nanofluid. Miklavčič and Wang's (Miklavčič and Wang, 2004) [9] MW roughness model are utilized in the presence of MHD of Cu-water nanofluid with enforcement of axial flows. This study will investigate the instability characteristics with the MHD boundary layer flow of nanofluid over a rotating disk and incorporate the effects of axial flow with anisotropic and isotropic surface roughness. The resulting ordinary differential equations (ODEs) are obtained by using von Kàrmàn (Kármán, 1921) [3] similarity transformation on partial differential equations (PDEs). Subsequently, numerical solutions are obtained using the shooting method, specifically the Runge-Kutta technique. Steady-flow profiles for MHD and volume fractions of nanoparticles are analyzed by the partial-slip conditions with surface roughness. Convective instability for stationary modes and neutral stability curves are also obtained and investigated by the formulation of linear stability equations with the MHD of nanofluid. Linear convective growth rates are utilized to analyze the stability of magnetic fields and nanoparticles and to confirm the outcomes of this analysis. Stationary disturbances are also considered in the energy analysis. The investigation indicates the correlation between instability modes Type I and Type II, in the presence of MHD, nanoparticles, and the growth rates of the critical Reynolds number. An integral energy equation enhances comprehension of the fundamental physical mechanisms. The factors contributing to convective instability in the system are clarified using this approach.
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@article {pmid38509923,
year = {2024},
author = {Iqra, T and Nadeem, S and Ghazwani, HA and Duraihem, FZ and Alzabut, J},
title = {Instability analysis for MHD boundary layer flow of nanofluid over a rotating disk with anisotropic and isotropic roughness.},
journal = {Heliyon},
volume = {10},
number = {6},
pages = {e26779},
pmid = {38509923},
issn = {2405-8440},
abstract = {The study focuses on the instability of local linear convective flow in an incompressible boundary layer caused by a rough rotating disk in a steady MHD flow of viscous nanofluid. Miklavčič and Wang's (Miklavčič and Wang, 2004) [9] MW roughness model are utilized in the presence of MHD of Cu-water nanofluid with enforcement of axial flows. This study will investigate the instability characteristics with the MHD boundary layer flow of nanofluid over a rotating disk and incorporate the effects of axial flow with anisotropic and isotropic surface roughness. The resulting ordinary differential equations (ODEs) are obtained by using von Kàrmàn (Kármán, 1921) [3] similarity transformation on partial differential equations (PDEs). Subsequently, numerical solutions are obtained using the shooting method, specifically the Runge-Kutta technique. Steady-flow profiles for MHD and volume fractions of nanoparticles are analyzed by the partial-slip conditions with surface roughness. Convective instability for stationary modes and neutral stability curves are also obtained and investigated by the formulation of linear stability equations with the MHD of nanofluid. Linear convective growth rates are utilized to analyze the stability of magnetic fields and nanoparticles and to confirm the outcomes of this analysis. Stationary disturbances are also considered in the energy analysis. The investigation indicates the correlation between instability modes Type I and Type II, in the presence of MHD, nanoparticles, and the growth rates of the critical Reynolds number. An integral energy equation enhances comprehension of the fundamental physical mechanisms. The factors contributing to convective instability in the system are clarified using this approach.},
}
RevDate: 2024-03-21
Multigrid simulations of non-Newtonian fluid flow and heat transfer in a ventilated square cavity with mixed convection and baffles.
Scientific reports, 14(1):6694.
The impact of baffles on a convective heat transfer of a non-Newtonian fluid is experimentally studied within a square cavity. The non-Newtonian fluid is pumped into the cavity through the inlet and subsequently departs from the cavity via the outlet. Given the inherent non-linearity of the model, a numerical technique has been selected as the method for obtaining the outcomes. Primarily, the governing equations within the two-dimensional domain have been discretized using the finite element method. For approximating velocity and pressure, we have employed the reliable P 2 - P 1 finite element pair, while for temperature, we have opted for the quadratic basis. To enhance convergence speed and accuracy, we employ the powerful multigrid approach. This study investigates how key parameters like Richardson number (Ri), Reynolds number (Re), and baffle gap b g influence heat transfer within a cavity comprising a non-Newtonian fluid. The baffle gap (b g) has been systematically altered within the range of 0.2-0.6, and for this research, three distinct power law indices have been selected namely: 0.5, 1.0, and 1.5. The primary outcomes of the investigation are illustrated through velocity profiles, streamlines, and isotherm visualizations. Furthermore, the study includes the computation of the Nu avg (average Nusselt number) across a range of parameter values. As the Richardson number (Ri) increases, Nu avg also rises, indicating that an increase in Ri results in augmented average heat transfer. Making the space between the baffles wider makes heat flow more intense. This, in turn, heats up more fluid within the cavity.
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@article {pmid38509193,
year = {2024},
author = {Rehman, N and Mahmood, R and Majeed, AH and Khan, I and Mohamed, A},
title = {Multigrid simulations of non-Newtonian fluid flow and heat transfer in a ventilated square cavity with mixed convection and baffles.},
journal = {Scientific reports},
volume = {14},
number = {1},
pages = {6694},
pmid = {38509193},
issn = {2045-2322},
abstract = {The impact of baffles on a convective heat transfer of a non-Newtonian fluid is experimentally studied within a square cavity. The non-Newtonian fluid is pumped into the cavity through the inlet and subsequently departs from the cavity via the outlet. Given the inherent non-linearity of the model, a numerical technique has been selected as the method for obtaining the outcomes. Primarily, the governing equations within the two-dimensional domain have been discretized using the finite element method. For approximating velocity and pressure, we have employed the reliable P 2 - P 1 finite element pair, while for temperature, we have opted for the quadratic basis. To enhance convergence speed and accuracy, we employ the powerful multigrid approach. This study investigates how key parameters like Richardson number (Ri), Reynolds number (Re), and baffle gap b g influence heat transfer within a cavity comprising a non-Newtonian fluid. The baffle gap (b g) has been systematically altered within the range of 0.2-0.6, and for this research, three distinct power law indices have been selected namely: 0.5, 1.0, and 1.5. The primary outcomes of the investigation are illustrated through velocity profiles, streamlines, and isotherm visualizations. Furthermore, the study includes the computation of the Nu avg (average Nusselt number) across a range of parameter values. As the Richardson number (Ri) increases, Nu avg also rises, indicating that an increase in Ri results in augmented average heat transfer. Making the space between the baffles wider makes heat flow more intense. This, in turn, heats up more fluid within the cavity.},
}
RevDate: 2024-03-19
Water Impalement Resistance and Drag Reduction of the Superhydrophobic Surface with Hydrophilic Strips.
ACS applied materials & interfaces [Epub ahead of print].
Superhydrophobic surfaces (SHS) offer versatile applications by trapping an air layer within microstructures, while water jet impact can destabilize this air layer and deactivate the functions of the SHS. The current work presents for the first time that introducing parallel hydrophilic strips to SHS (SHS-s) can simultaneously improve both water impalement resistance and drag reduction (DR). Compared with SHS, SHS-s demonstrates a 125% increase in the enduring time against the impact of water jet with velocity of 11.9 m/s and a 97% improvement in DR at a Reynolds number of 1.4 × 10[4]. The key mechanism lies in the enhanced stability of the air layer due to air confinement by the adjacent three-phase contact lines. These lines not only impede air drainage through the surface microstructures during water jet impact, entrapping the air layer to resist water impalement, but also prevent air floating up due to buoyancy in Taylor-Couette flow, ensuring an even spread of the air layer all over the rotor, boosting DR. Moreover, failure modes of SHS under water jet impact are revealed to be related to air layer decay and surface structure destruction. This mass-producible structured surface holds the potential for widespread use in DR for hulls, autonomous underwater vehicles, and submarines.
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@article {pmid38502909,
year = {2024},
author = {Cao, Y and Liu, X and Zhang, L and Wu, Y and You, C and Li, H and Duan, H and Huang, J and Lv, P},
title = {Water Impalement Resistance and Drag Reduction of the Superhydrophobic Surface with Hydrophilic Strips.},
journal = {ACS applied materials & interfaces},
volume = {},
number = {},
pages = {},
doi = {10.1021/acsami.3c18905},
pmid = {38502909},
issn = {1944-8252},
abstract = {Superhydrophobic surfaces (SHS) offer versatile applications by trapping an air layer within microstructures, while water jet impact can destabilize this air layer and deactivate the functions of the SHS. The current work presents for the first time that introducing parallel hydrophilic strips to SHS (SHS-s) can simultaneously improve both water impalement resistance and drag reduction (DR). Compared with SHS, SHS-s demonstrates a 125% increase in the enduring time against the impact of water jet with velocity of 11.9 m/s and a 97% improvement in DR at a Reynolds number of 1.4 × 10[4]. The key mechanism lies in the enhanced stability of the air layer due to air confinement by the adjacent three-phase contact lines. These lines not only impede air drainage through the surface microstructures during water jet impact, entrapping the air layer to resist water impalement, but also prevent air floating up due to buoyancy in Taylor-Couette flow, ensuring an even spread of the air layer all over the rotor, boosting DR. Moreover, failure modes of SHS under water jet impact are revealed to be related to air layer decay and surface structure destruction. This mass-producible structured surface holds the potential for widespread use in DR for hulls, autonomous underwater vehicles, and submarines.},
}
RevDate: 2024-03-19
Intrinsic dissolution rate modeling for the pharmacopoeia apparatus rotating disk compared to flow channel method.
Pharmaceutical development and technology [Epub ahead of print].
For a solid understanding of drug characteristics, in vitro measurement of the intrinsic dissolution rate is important. Hydrodynamics are often emphasized as the decisive parameter influencing the dissolution. In this study, experiments and computational fluid dynamic (CFD) simulations showed that the mixing behavior in the rotating disc apparatus causes an inhomogeneous flow field and a systematic error in the calculation of the intrinsic dissolution rate. This error is affected by both the experimental time and the velocity. Due to the rotational movement around the tablet center, commonly utilized in pharmacopeia methods, a broad variance is present with regard to the impact of fluid velocity on individual particles of the specimen surface. As this is significantly reduced in the case of uniform overflow, the flow channel is recommended for investigating the dissolution behavior. It is shown that rotating disc measurements can be compared with flow channel measurements after adjusting the measured data for the rotating disc based on a proposed, representative Reynolds number and a suggested apparatus-dependent correction factor. Additionally, modeling the apparatus-independent intrinsic dissolution rate for different temperatures in the rotating disc apparatus is possible using the adapted Levich's equation.
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@article {pmid38501605,
year = {2024},
author = {Mattusch, AM and Schaldach, G and Bartsch, J and Thommes, M},
title = {Intrinsic dissolution rate modeling for the pharmacopoeia apparatus rotating disk compared to flow channel method.},
journal = {Pharmaceutical development and technology},
volume = {},
number = {},
pages = {1-10},
doi = {10.1080/10837450.2024.2329115},
pmid = {38501605},
issn = {1097-9867},
abstract = {For a solid understanding of drug characteristics, in vitro measurement of the intrinsic dissolution rate is important. Hydrodynamics are often emphasized as the decisive parameter influencing the dissolution. In this study, experiments and computational fluid dynamic (CFD) simulations showed that the mixing behavior in the rotating disc apparatus causes an inhomogeneous flow field and a systematic error in the calculation of the intrinsic dissolution rate. This error is affected by both the experimental time and the velocity. Due to the rotational movement around the tablet center, commonly utilized in pharmacopeia methods, a broad variance is present with regard to the impact of fluid velocity on individual particles of the specimen surface. As this is significantly reduced in the case of uniform overflow, the flow channel is recommended for investigating the dissolution behavior. It is shown that rotating disc measurements can be compared with flow channel measurements after adjusting the measured data for the rotating disc based on a proposed, representative Reynolds number and a suggested apparatus-dependent correction factor. Additionally, modeling the apparatus-independent intrinsic dissolution rate for different temperatures in the rotating disc apparatus is possible using the adapted Levich's equation.},
}
RevDate: 2024-03-17
Mathematical formulation and computation of the dynamics of blood flow, heat and mass transfer during MRI scanning.
Scientific reports, 14(1):6364.
Computational modeling of arterial blood flow, heat and mass transfer during MRI scanning is studied. The flow is assumed to be unsteady, in-compressible, and asymmetric. Mathematical formulation considers the presence of stenosis, joule heating viscous dissipation and chemical reaction. The explicit finite difference scheme is used to numerically solve the model equations. The MATLAB software was used to plot the graphical results. The study reveals that, during MRI scanning, both radial and axial velocities diminish with increase in the strength of magnetic fields. Besides, the study found that, Eckert number and Hartman number enhance the blood's temperature and the same, diminishes with increase in Prandtl and Reynolds numbers. Concentration profile is observed to decline with increase in chemical reaction parameter, Schmidt number and Reynolds number. Soret number on the other hand, is observed to positively influence the concentration.
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@article {pmid38493264,
year = {2024},
author = {Mwapinga, A},
title = {Mathematical formulation and computation of the dynamics of blood flow, heat and mass transfer during MRI scanning.},
journal = {Scientific reports},
volume = {14},
number = {1},
pages = {6364},
pmid = {38493264},
issn = {2045-2322},
abstract = {Computational modeling of arterial blood flow, heat and mass transfer during MRI scanning is studied. The flow is assumed to be unsteady, in-compressible, and asymmetric. Mathematical formulation considers the presence of stenosis, joule heating viscous dissipation and chemical reaction. The explicit finite difference scheme is used to numerically solve the model equations. The MATLAB software was used to plot the graphical results. The study reveals that, during MRI scanning, both radial and axial velocities diminish with increase in the strength of magnetic fields. Besides, the study found that, Eckert number and Hartman number enhance the blood's temperature and the same, diminishes with increase in Prandtl and Reynolds numbers. Concentration profile is observed to decline with increase in chemical reaction parameter, Schmidt number and Reynolds number. Soret number on the other hand, is observed to positively influence the concentration.},
}
RevDate: 2024-03-12
Dynamic similarity and the peculiar allometry of maximum running speed.
Nature communications, 15(1):2181.
Animal performance fundamentally influences behaviour, ecology, and evolution. It typically varies monotonously with size. A notable exception is maximum running speed; the fastest animals are of intermediate size. Here we show that this peculiar allometry results from the competition between two musculoskeletal constraints: the kinetic energy capacity, which dominates in small animals, and the work capacity, which reigns supreme in large animals. The ratio of both capacities defines the physiological similarity index Γ, a dimensionless number akin to the Reynolds number in fluid mechanics. The scaling of Γ indicates a transition from a dominance of muscle forces to a dominance of inertial forces as animals grow in size; its magnitude defines conditions of "dynamic similarity" that enable comparison and estimates of locomotor performance across extant and extinct animals; and the physical parameters that define it highlight opportunities for adaptations in musculoskeletal "design" that depart from the eternal null hypothesis of geometric similarity. The physiological similarity index challenges the Froude number as prevailing dynamic similarity condition, reveals that the differential growth of muscle and weight forces central to classic scaling theory is of secondary importance for the majority of terrestrial animals, and suggests avenues for comparative analyses of locomotor systems.
Additional Links: PMID-38467620
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@article {pmid38467620,
year = {2024},
author = {Labonte, D and Bishop, PJ and Dick, TJM and Clemente, CJ},
title = {Dynamic similarity and the peculiar allometry of maximum running speed.},
journal = {Nature communications},
volume = {15},
number = {1},
pages = {2181},
pmid = {38467620},
issn = {2041-1723},
support = {851705//EC | EU Framework Programme for Research and Innovation H2020 | H2020 Priority Excellent Science | H2020 European Research Council (H2020 Excellent Science - European Research Council)/ ; RGY0073/2020//Human Frontier Science Program (HFSP)/ ; },
abstract = {Animal performance fundamentally influences behaviour, ecology, and evolution. It typically varies monotonously with size. A notable exception is maximum running speed; the fastest animals are of intermediate size. Here we show that this peculiar allometry results from the competition between two musculoskeletal constraints: the kinetic energy capacity, which dominates in small animals, and the work capacity, which reigns supreme in large animals. The ratio of both capacities defines the physiological similarity index Γ, a dimensionless number akin to the Reynolds number in fluid mechanics. The scaling of Γ indicates a transition from a dominance of muscle forces to a dominance of inertial forces as animals grow in size; its magnitude defines conditions of "dynamic similarity" that enable comparison and estimates of locomotor performance across extant and extinct animals; and the physical parameters that define it highlight opportunities for adaptations in musculoskeletal "design" that depart from the eternal null hypothesis of geometric similarity. The physiological similarity index challenges the Froude number as prevailing dynamic similarity condition, reveals that the differential growth of muscle and weight forces central to classic scaling theory is of secondary importance for the majority of terrestrial animals, and suggests avenues for comparative analyses of locomotor systems.},
}
RevDate: 2024-03-11
Some effects of domain size and boundary conditions on the accuracy of airfoil simulations.
Advances in aerodynamics, 6(1):7.
This paper investigates a specific case of one of the most popular fluid dynamic simulations, the incompressible flow around an airfoil (NACA 0012 here) at a high Reynolds number (6×106). OpenFOAM software was used to study the effect of domain size and four common choices of boundary conditions on airfoil lift, drag, surface friction, and pressure. We also examine the relation between boundary conditions and the velocity, pressure, and vorticity distributions throughout the domain. In addition to the common boundary conditions, we implement the "point vortex" boundary condition that was introduced many years ago but is now rarely used. We also applied the point vortex condition for the outlet pressure instead of using the traditional Neumann condition. With the airfoil generating significant lift at incidence angles of 5∘,10∘, and 14∘, we confirm a previous finding that the boundary conditions combine with domain size to produce an induced (pressure) drag. The change in the pressure drag with domain size is significant for the commonly-used boundary conditions but is much smaller for the point vortex alternative. The point vortex boundary condition increases the execution time, but this is more than offset by the reduction in domain size needed to achieve a specified accuracy in the lift and drag. This study also estimates the error in total drag and lift due to domain size and shows it can be almost eliminated using the point vortex boundary condition. We also used the impulse form of the momentum equations to study the relation between drag and lift and spurious vorticity, which is generated as a result of using non-exact boundary conditions. These equations reveal that the spurious vorticity throughout the domain is associated with cancelling circulation around the domain boundaries.
Additional Links: PMID-38464493
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@article {pmid38464493,
year = {2024},
author = {Golmirzaee, N and Wood, DH},
title = {Some effects of domain size and boundary conditions on the accuracy of airfoil simulations.},
journal = {Advances in aerodynamics},
volume = {6},
number = {1},
pages = {7},
pmid = {38464493},
issn = {2524-6992},
abstract = {This paper investigates a specific case of one of the most popular fluid dynamic simulations, the incompressible flow around an airfoil (NACA 0012 here) at a high Reynolds number (6×106). OpenFOAM software was used to study the effect of domain size and four common choices of boundary conditions on airfoil lift, drag, surface friction, and pressure. We also examine the relation between boundary conditions and the velocity, pressure, and vorticity distributions throughout the domain. In addition to the common boundary conditions, we implement the "point vortex" boundary condition that was introduced many years ago but is now rarely used. We also applied the point vortex condition for the outlet pressure instead of using the traditional Neumann condition. With the airfoil generating significant lift at incidence angles of 5∘,10∘, and 14∘, we confirm a previous finding that the boundary conditions combine with domain size to produce an induced (pressure) drag. The change in the pressure drag with domain size is significant for the commonly-used boundary conditions but is much smaller for the point vortex alternative. The point vortex boundary condition increases the execution time, but this is more than offset by the reduction in domain size needed to achieve a specified accuracy in the lift and drag. This study also estimates the error in total drag and lift due to domain size and shows it can be almost eliminated using the point vortex boundary condition. We also used the impulse form of the momentum equations to study the relation between drag and lift and spurious vorticity, which is generated as a result of using non-exact boundary conditions. These equations reveal that the spurious vorticity throughout the domain is associated with cancelling circulation around the domain boundaries.},
}
RevDate: 2024-03-11
The impact of multiple stenosis and aneurysms on arterial diseases: A cardiovascular study.
Heliyon, 10(5):e26889.
The comparative effect of serial stenosis and aneurysms arteries on blood flow is examined to identify atherosclerotic diseases. The finite element approach has been used to solve the continuity, momentum, and Oldroyd-B partial differential equations to analyze the blood flow. Newtonian and non-Newtonian both cases are taken for the viscoelastic response of blood. In this study, the impact of multiple stenotic and aneurysmal arteries on blood flow have been studied to determine the severity of atherosclerosis diseases through the analysis of blood behavior. The novel aspect of the study is its assessment of the severity of atherosclerotic disorders for the occurrence of serial stenosis and aneurysm simultaneously in the blood vessel wall in each of the four cases. The maximum abnormal arterial blood flow effect is found for the presence of serial stenoses compared to aneurysms which refers to the severity of atherosclerosis. At the hub of stenosis, the blood velocity magnitude and wall shear stress (WSS) are higher, whereas the arterial wall normal gradient values are lower. For all cases, the contrary results are observed at the hub of the aneurysmal model. The blood flow has been affected significantly by the increases in Reynolds number for both models. The influence of stenotic and aneurysmal arteries on blood flow is graphically illustrated in terms of the velocity profile, pressure distribution, and WSS. Medical experts may use this study's findings to assess the severity of cardiovascular diseases.
Additional Links: PMID-38463765
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@article {pmid38463765,
year = {2024},
author = {Uddin, MN and Hoque, KE and Billah, MM},
title = {The impact of multiple stenosis and aneurysms on arterial diseases: A cardiovascular study.},
journal = {Heliyon},
volume = {10},
number = {5},
pages = {e26889},
pmid = {38463765},
issn = {2405-8440},
abstract = {The comparative effect of serial stenosis and aneurysms arteries on blood flow is examined to identify atherosclerotic diseases. The finite element approach has been used to solve the continuity, momentum, and Oldroyd-B partial differential equations to analyze the blood flow. Newtonian and non-Newtonian both cases are taken for the viscoelastic response of blood. In this study, the impact of multiple stenotic and aneurysmal arteries on blood flow have been studied to determine the severity of atherosclerosis diseases through the analysis of blood behavior. The novel aspect of the study is its assessment of the severity of atherosclerotic disorders for the occurrence of serial stenosis and aneurysm simultaneously in the blood vessel wall in each of the four cases. The maximum abnormal arterial blood flow effect is found for the presence of serial stenoses compared to aneurysms which refers to the severity of atherosclerosis. At the hub of stenosis, the blood velocity magnitude and wall shear stress (WSS) are higher, whereas the arterial wall normal gradient values are lower. For all cases, the contrary results are observed at the hub of the aneurysmal model. The blood flow has been affected significantly by the increases in Reynolds number for both models. The influence of stenotic and aneurysmal arteries on blood flow is graphically illustrated in terms of the velocity profile, pressure distribution, and WSS. Medical experts may use this study's findings to assess the severity of cardiovascular diseases.},
}
RevDate: 2024-03-08
Dynamics of cavitation bubbles in viscous liquids in a tube during a transient process.
Ultrasonics sonochemistry, 104:106840 pii:S1350-4177(24)00088-9 [Epub ahead of print].
We experimentally, numerically, and theoretically investigate the dynamics of cavitation bubbles in viscous liquids in a tube during a transient process. In experiments, cavitation bubbles are generated by a modified tube-arrest setup, and the bubble evolution is captured with high-speed imaging. Numerical simulations using OpenFOAM are employed to validate our quasi-one-dimensional theoretical model, which effectively characterizes the bubble dynamics. We find that cavitation onset is minimally affected by the liquid viscosity. However, once cavitation occurs, various aspects of bubble dynamics, such as the maximum bubble length, bubble lifetime, collapse time, and collapse speed, are closely related to the liquid viscosity. We further establish that normalized bubble dynamics are solely determined by the combination of the Reynolds number and the Euler number. Moreover, we also propose a new dimensionless number, Ca2, to predict the maximum bubble length, a critical factor in determining the occurrence of liquid column separation.
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@article {pmid38457940,
year = {2024},
author = {Wang, Z and Xu, P and Ren, Z and Yu, L and Zuo, Z and Liu, S},
title = {Dynamics of cavitation bubbles in viscous liquids in a tube during a transient process.},
journal = {Ultrasonics sonochemistry},
volume = {104},
number = {},
pages = {106840},
doi = {10.1016/j.ultsonch.2024.106840},
pmid = {38457940},
issn = {1873-2828},
abstract = {We experimentally, numerically, and theoretically investigate the dynamics of cavitation bubbles in viscous liquids in a tube during a transient process. In experiments, cavitation bubbles are generated by a modified tube-arrest setup, and the bubble evolution is captured with high-speed imaging. Numerical simulations using OpenFOAM are employed to validate our quasi-one-dimensional theoretical model, which effectively characterizes the bubble dynamics. We find that cavitation onset is minimally affected by the liquid viscosity. However, once cavitation occurs, various aspects of bubble dynamics, such as the maximum bubble length, bubble lifetime, collapse time, and collapse speed, are closely related to the liquid viscosity. We further establish that normalized bubble dynamics are solely determined by the combination of the Reynolds number and the Euler number. Moreover, we also propose a new dimensionless number, Ca2, to predict the maximum bubble length, a critical factor in determining the occurrence of liquid column separation.},
}
RevDate: 2024-03-06
The motion of micro-swimmers over a cavity in a micro-channel.
Soft matter [Epub ahead of print].
This article combines the lattice Boltzmann method (LBM) with the squirmer model to investigate the motion of micro-swimmers in a channel-cavity system. The study analyses various influential factors, including the value of the squirmer-type factor (β), the swimming Reynolds number (Rep), the size of the cavity, initial position and particle size on the movement of micro-swimmers within the channel-cavity system. We simultaneously studied three types of squirmer models, Puller (β > 0), Pusher (β < 0), and Neutral (β = 0) swimmers. The findings reveal that the motion of micro-swimmers is determined by the value of β and Rep, which can be classified into six distinct motion modes. For Puller and Pusher, when the β value is constant, an increase in Rep will lead to transition in the motion mode. Moreover, the appropriate depth of cavity within the channel-cavity system plays a crucial role in capturing and separating Neutral swimmers. This study, for the first time, explores the effect of complex channel-cavity systems on the behaviour of micro-swimmers and highlights their separation and capture ability. These findings offer novel insights for the design and enhancement of micro-channel structures in achieving efficient separation and capture of micro-swimmers.
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@article {pmid38445957,
year = {2024},
author = {Hu, X and Chen, W and Lin, J and Nie, D and Zhu, Z and Lin, P},
title = {The motion of micro-swimmers over a cavity in a micro-channel.},
journal = {Soft matter},
volume = {},
number = {},
pages = {},
doi = {10.1039/d3sm01589k},
pmid = {38445957},
issn = {1744-6848},
abstract = {This article combines the lattice Boltzmann method (LBM) with the squirmer model to investigate the motion of micro-swimmers in a channel-cavity system. The study analyses various influential factors, including the value of the squirmer-type factor (β), the swimming Reynolds number (Rep), the size of the cavity, initial position and particle size on the movement of micro-swimmers within the channel-cavity system. We simultaneously studied three types of squirmer models, Puller (β > 0), Pusher (β < 0), and Neutral (β = 0) swimmers. The findings reveal that the motion of micro-swimmers is determined by the value of β and Rep, which can be classified into six distinct motion modes. For Puller and Pusher, when the β value is constant, an increase in Rep will lead to transition in the motion mode. Moreover, the appropriate depth of cavity within the channel-cavity system plays a crucial role in capturing and separating Neutral swimmers. This study, for the first time, explores the effect of complex channel-cavity systems on the behaviour of micro-swimmers and highlights their separation and capture ability. These findings offer novel insights for the design and enhancement of micro-channel structures in achieving efficient separation and capture of micro-swimmers.},
}
RevDate: 2024-03-04
Adaptive urban drinking water supply model using the effect of node elevation and head loss formula: A case study.
Heliyon, 10(5):e26181.
Along with population growth and health improvement, water demand due to urbanization is increasing and creating a need to develop a strategy for handling water supply networks (WSNs). In the last decade, software modeling of WSNs has been developed to evaluate the state of networks in terms of pressure control, leakage analysis, and overall demand determination. In the case of very complex and extremely large networks, it is very difficult to manage the water supply. Metropolitan Waterworks Authority (MWA) in Thailand has to supply drinking water to the three densely populated cities; Bangkok, Nonthaburi, and Samut Prakan, that cover an area of 2944.05 km[2]. Hence, MWA has developed a main pipe model using EPANET software as a managing tool. This tool can offer a good solution for the water supply, but there is approximately a 14 percent error, mainly due to not having the elevation data of the pipe network. The current research is based on demand and pressure modeling analysis with utilizing two important parameters, node elevations, and head loss. The first trial model was an initial revision of the node elevation based on a road surface map. It was found that the model with elevation data could offer a better solution and was 3.95% more accurate than the existing model. The result was significantly improved, but another error, which may have been caused by using an inappropriate head loss model, was found. As the introduced model is based on the Hazen-William model, it cannot offer an accurate solution for all Reynolds number ranges. Even though Darcy-Weisbach is more complex to use, it could provide a better solution. The results indicate the Darcy-Weisbach model produces results that are 8.65% more accurate than the Hazen-William model.
Additional Links: PMID-38434303
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@article {pmid38434303,
year = {2024},
author = {Wannapop, R and Jearsiripongkul, T and Jiamjiroch, K},
title = {Adaptive urban drinking water supply model using the effect of node elevation and head loss formula: A case study.},
journal = {Heliyon},
volume = {10},
number = {5},
pages = {e26181},
pmid = {38434303},
issn = {2405-8440},
abstract = {Along with population growth and health improvement, water demand due to urbanization is increasing and creating a need to develop a strategy for handling water supply networks (WSNs). In the last decade, software modeling of WSNs has been developed to evaluate the state of networks in terms of pressure control, leakage analysis, and overall demand determination. In the case of very complex and extremely large networks, it is very difficult to manage the water supply. Metropolitan Waterworks Authority (MWA) in Thailand has to supply drinking water to the three densely populated cities; Bangkok, Nonthaburi, and Samut Prakan, that cover an area of 2944.05 km[2]. Hence, MWA has developed a main pipe model using EPANET software as a managing tool. This tool can offer a good solution for the water supply, but there is approximately a 14 percent error, mainly due to not having the elevation data of the pipe network. The current research is based on demand and pressure modeling analysis with utilizing two important parameters, node elevations, and head loss. The first trial model was an initial revision of the node elevation based on a road surface map. It was found that the model with elevation data could offer a better solution and was 3.95% more accurate than the existing model. The result was significantly improved, but another error, which may have been caused by using an inappropriate head loss model, was found. As the introduced model is based on the Hazen-William model, it cannot offer an accurate solution for all Reynolds number ranges. Even though Darcy-Weisbach is more complex to use, it could provide a better solution. The results indicate the Darcy-Weisbach model produces results that are 8.65% more accurate than the Hazen-William model.},
}
RevDate: 2024-03-02
An analytical and comparative study of swallowing in a tumor-infected oesophagus: a mathematical model.
Journal of mathematical biology, 88(3):37.
This study discusses non-steady effects encountered in peristaltic flows in oesophagus. The purpose of this communication is to evolve a mechanism to diagnose tumor in an oesophagus mathematically. The tumor is modelled by generic bump function of certain height and width. The method of solution follows long wavelength and low-Reynolds number approximations for unsteady flow, while integrations have been performed numerically in order to plot graphs, which reveal various characteristics of the flow. The goal is to assess how pressure varies across the tumor's width. The spatial, as well as temporal, dependence of pressure has been studied in the laboratory frame of reference. The pressure distribution for tumor-infected oesophagus is compared with that of normal oesophagus. An intensified pressure is obtained in the presence of tumor. The interruption while swallowing through benign oesophageal tumor is confirmed by an abrupt pressure rise across the tumor's width. Tumor position also plays a significant role whether it is at contraction or relaxation of walls. Additionally, wall-shear-stress, volumetric flow rate and streamlines have also been described and compared with that without tumor growth. The expressions corresponding to all the physical quantities are computed numerically. Further, this model may also be implemented to the two-dimensional channel flow for an industrial application.
Additional Links: PMID-38430250
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@article {pmid38430250,
year = {2024},
author = {Pandey, SK and Prajapati, A},
title = {An analytical and comparative study of swallowing in a tumor-infected oesophagus: a mathematical model.},
journal = {Journal of mathematical biology},
volume = {88},
number = {3},
pages = {37},
pmid = {38430250},
issn = {1432-1416},
abstract = {This study discusses non-steady effects encountered in peristaltic flows in oesophagus. The purpose of this communication is to evolve a mechanism to diagnose tumor in an oesophagus mathematically. The tumor is modelled by generic bump function of certain height and width. The method of solution follows long wavelength and low-Reynolds number approximations for unsteady flow, while integrations have been performed numerically in order to plot graphs, which reveal various characteristics of the flow. The goal is to assess how pressure varies across the tumor's width. The spatial, as well as temporal, dependence of pressure has been studied in the laboratory frame of reference. The pressure distribution for tumor-infected oesophagus is compared with that of normal oesophagus. An intensified pressure is obtained in the presence of tumor. The interruption while swallowing through benign oesophageal tumor is confirmed by an abrupt pressure rise across the tumor's width. Tumor position also plays a significant role whether it is at contraction or relaxation of walls. Additionally, wall-shear-stress, volumetric flow rate and streamlines have also been described and compared with that without tumor growth. The expressions corresponding to all the physical quantities are computed numerically. Further, this model may also be implemented to the two-dimensional channel flow for an industrial application.},
}
RevDate: 2024-03-01
Viscosimetric squeeze flow of suspensions.
The European physical journal. E, Soft matter, 47(3):17.
The rheology of particle suspensions has been extensively explored in the case of a simple shear flow, but less in other flow configurations which are also important in practice. Here we investigate the behavior of a suspension in a squeeze flow, which we revisit using local pressure measurements to deduce the effective viscosity. The flow is generated by approaching a moving disk to a fixed wall at constant velocity in the low Reynolds number limit. We measure the evolution of the pressure field at the wall and deduce the effective viscosity from the radial pressure drop. After validation of our device using a Newtonian fluid, we measure the effective viscosity of a suspension for different squeezing speeds and volume fractions of particles. We find results in agreement with the Maron-Pierce law, an empirical expression for the viscosity of suspensions that was established for simple shear flows. We prove that this method to determine viscosity remains valid in the limit of large gap width. This makes it possible to study the rheology of suspensions within this limit and therefore suspensions composed of large particles, in contrast to Couette flow cells which require small gaps.
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@article {pmid38427109,
year = {2024},
author = {Zidi, K and Texier, BD and Gauthier, G and Seguin, A},
title = {Viscosimetric squeeze flow of suspensions.},
journal = {The European physical journal. E, Soft matter},
volume = {47},
number = {3},
pages = {17},
pmid = {38427109},
issn = {1292-895X},
support = {ANR-10-LABX-0039-PALM//Laboratoire d'excellence Physique Atomes Lumière Matière/ ; },
abstract = {The rheology of particle suspensions has been extensively explored in the case of a simple shear flow, but less in other flow configurations which are also important in practice. Here we investigate the behavior of a suspension in a squeeze flow, which we revisit using local pressure measurements to deduce the effective viscosity. The flow is generated by approaching a moving disk to a fixed wall at constant velocity in the low Reynolds number limit. We measure the evolution of the pressure field at the wall and deduce the effective viscosity from the radial pressure drop. After validation of our device using a Newtonian fluid, we measure the effective viscosity of a suspension for different squeezing speeds and volume fractions of particles. We find results in agreement with the Maron-Pierce law, an empirical expression for the viscosity of suspensions that was established for simple shear flows. We prove that this method to determine viscosity remains valid in the limit of large gap width. This makes it possible to study the rheology of suspensions within this limit and therefore suspensions composed of large particles, in contrast to Couette flow cells which require small gaps.},
}
RevDate: 2024-02-27
Influence of inclined magnetic field and heat transfer on the peristaltic flow of Rabinowitsch fluid model in an inclined channel.
Scientific reports, 14(1):4735.
The recent study is focused on discussion of heat transfer and magnetic field results of peristaltic flow of Rabinowitsch fluid model in an Inclined Channel. In this piece of research, peristalsis's fundamental problem with heat transfer in the presence of a magnetic field is checked. An incompressible Rabinowitsch fluid is present in an inclined channel, which is considered as the reference for this research. The solutions are devised with the assumptions of long wavelength and low Reynolds number approximations. The resulting equations are then solved exactly by implementing various command of MATHEMATICA subject to relevant boundary conditions. Results are discussed for various flow quantities like temperature, velocity, tangential stress, pressure gradient and rise, and friction force. Computational simulations are performed to determine the flow quantities. This investigation goes beyond mere calculations and examines particle motion to gain deeper insights into flow quantities. Furthermore, this investigates how magnetic field and heat transfer parameters influence these peristaltic flow phenomena. The outcomes of important parameters were plotted and scrutinized. There is amultitude of medical implementations derived from the current consideration, such as the depiction of the gastric juice motion in the small intestine when an endoscope is inserted through it.
Additional Links: PMID-38413619
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@article {pmid38413619,
year = {2024},
author = {Elmhedy, Y and Abd-Alla, AM and Abo-Dahab, SM and Alharbi, FM and Abdelhafez, MA},
title = {Influence of inclined magnetic field and heat transfer on the peristaltic flow of Rabinowitsch fluid model in an inclined channel.},
journal = {Scientific reports},
volume = {14},
number = {1},
pages = {4735},
pmid = {38413619},
issn = {2045-2322},
abstract = {The recent study is focused on discussion of heat transfer and magnetic field results of peristaltic flow of Rabinowitsch fluid model in an Inclined Channel. In this piece of research, peristalsis's fundamental problem with heat transfer in the presence of a magnetic field is checked. An incompressible Rabinowitsch fluid is present in an inclined channel, which is considered as the reference for this research. The solutions are devised with the assumptions of long wavelength and low Reynolds number approximations. The resulting equations are then solved exactly by implementing various command of MATHEMATICA subject to relevant boundary conditions. Results are discussed for various flow quantities like temperature, velocity, tangential stress, pressure gradient and rise, and friction force. Computational simulations are performed to determine the flow quantities. This investigation goes beyond mere calculations and examines particle motion to gain deeper insights into flow quantities. Furthermore, this investigates how magnetic field and heat transfer parameters influence these peristaltic flow phenomena. The outcomes of important parameters were plotted and scrutinized. There is amultitude of medical implementations derived from the current consideration, such as the depiction of the gastric juice motion in the small intestine when an endoscope is inserted through it.},
}
RevDate: 2024-02-26
A pressure-free long-time stable reduced-order model for two-dimensional Rayleigh-Bénard convection.
Chaos (Woodbury, N.Y.), 34(2):.
The present work presents a stable proper orthogonal decomposition (POD)-Galerkin based reduced-order model (ROM) for two-dimensional Rayleigh-Bénard convection in a square geometry for three Rayleigh numbers: 104 (steady state), 3×105 (periodic), and 6×106 (chaotic). Stability is obtained through a particular (staggered-grid) full-order model (FOM) discretization that leads to a ROM that is pressure-free and has skew-symmetric (energy-conserving) convective terms. This yields long-time stable solutions without requiring stabilizing mechanisms, even outside the training data range. The ROM's stability is validated for the different test cases by investigating the Nusselt and Reynolds number time series and the mean and variance of the vertical temperature profile. In general, these quantities converge to the FOM when increasing the number of modes, and turn out to be a good measure of accuracy. However, for the chaotic case, convergence with increasing numbers of modes is relatively difficult and a high number of modes is required to resolve the low-energy structures that are important for the global dynamics.
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@article {pmid38407396,
year = {2024},
author = {Chand, K and Rosenberger, H and Sanderse, B},
title = {A pressure-free long-time stable reduced-order model for two-dimensional Rayleigh-Bénard convection.},
journal = {Chaos (Woodbury, N.Y.)},
volume = {34},
number = {2},
pages = {},
doi = {10.1063/5.0168857},
pmid = {38407396},
issn = {1089-7682},
abstract = {The present work presents a stable proper orthogonal decomposition (POD)-Galerkin based reduced-order model (ROM) for two-dimensional Rayleigh-Bénard convection in a square geometry for three Rayleigh numbers: 104 (steady state), 3×105 (periodic), and 6×106 (chaotic). Stability is obtained through a particular (staggered-grid) full-order model (FOM) discretization that leads to a ROM that is pressure-free and has skew-symmetric (energy-conserving) convective terms. This yields long-time stable solutions without requiring stabilizing mechanisms, even outside the training data range. The ROM's stability is validated for the different test cases by investigating the Nusselt and Reynolds number time series and the mean and variance of the vertical temperature profile. In general, these quantities converge to the FOM when increasing the number of modes, and turn out to be a good measure of accuracy. However, for the chaotic case, convergence with increasing numbers of modes is relatively difficult and a high number of modes is required to resolve the low-energy structures that are important for the global dynamics.},
}
RevDate: 2024-02-21
Energetics of the mokicrosporidian polar tube invasion machinery.
eLife, 12: pii:86638.
Microsporidia are eukaryotic, obligate intracellular parasites that infect a wide range of hosts, leading to health and economic burdens worldwide. Microsporidia use an unusual 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 μm in size) shoot out a 100-nm-wide PT at a speed of 300 μm/s, creating a shear rate of 3000 s[-1]. The infectious cargo, which contains two nuclei, is shot through this narrow tube for a distance of ∼60-140 μm (Jaroenlak et al, 2020) 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. 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.
Additional Links: PMID-38381133
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PubMed:
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@article {pmid38381133,
year = {2024},
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 mokicrosporidian polar tube invasion machinery.},
journal = {eLife},
volume = {12},
number = {},
pages = {},
doi = {10.7554/eLife.86638},
pmid = {38381133},
issn = {2050-084X},
support = {HHMI Faculty fellowship/HHMI/Howard Hughes Medical Institute/United States ; R35GM128777/GM/NIGMS NIH HHS/United States ; },
abstract = {Microsporidia are eukaryotic, obligate intracellular parasites that infect a wide range of hosts, leading to health and economic burdens worldwide. Microsporidia use an unusual 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 μm in size) shoot out a 100-nm-wide PT at a speed of 300 μm/s, creating a shear rate of 3000 s[-1]. The infectious cargo, which contains two nuclei, is shot through this narrow tube for a distance of ∼60-140 μm (Jaroenlak et al, 2020) 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. 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.},
}
RevDate: 2024-02-20
Study on the Performance of a Surface with Coupled Wettability Difference and Convex-Stripe Array for Improved Air Layer Stability.
Langmuir : the ACS journal of surfaces and colloids [Epub ahead of print].
The existence of an air layer reduces friction drag on superhydrophobic surfaces. Therefore, improving the air layer stability of superhydrophobic surfaces holds immense significance in reducing both energy consumption and environmental pollution caused by friction drag. Based on the properties of mathematical discretization and the contact angle hysteresis generated by the wettability difference, a surface coupled with a wettability difference treatment and a convex-stripe array is developed by laser engraving and fluorine modification, and its performance in improving the air layer stability is experimentally studied in a von Kármán swirling flow field. The results show that the destabilization of the air layer is mainly caused by the Kelvin-Helmholtz instability, which is triggered by the density difference between gas and liquid, as well as the tangential velocity difference between gas and liquid. When the air layer is relatively thin, tangential wave destabilization occurs, whereas for larger thicknesses, the destabilization mode is coupled wave destabilization. The maximum Reynolds number that keeps the air layer fully covering the surface of the rotating disk (with drag reduction performance) during the disk rotation process is defined as the critical Reynolds number (Rec), which is 1.62 × 10[5] for the uniform superhydrophobic surface and 3.24 × 10[5] for the superhydrophobic surface with a convex stripe on the outermost ring (SCSSP). Individual treatments of wettability difference and a convex-stripe array on the SCSSP further improve the air layer stability, but Rec remains at 3.24 × 10[5]. Finally, the coupling of the wettability difference treatment with a convex-stripe array significantly improves the air layer stability, resulting in an increase of Rec to 4.05 × 10[5], and the drag reduction rate stably maintained around 30%.
Additional Links: PMID-38378438
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PubMed:
Citation:
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@article {pmid38378438,
year = {2024},
author = {Qiao, S and Cai, C and Pan, C and Liu, Y and Zhang, Q},
title = {Study on the Performance of a Surface with Coupled Wettability Difference and Convex-Stripe Array for Improved Air Layer Stability.},
journal = {Langmuir : the ACS journal of surfaces and colloids},
volume = {},
number = {},
pages = {},
doi = {10.1021/acs.langmuir.3c03929},
pmid = {38378438},
issn = {1520-5827},
abstract = {The existence of an air layer reduces friction drag on superhydrophobic surfaces. Therefore, improving the air layer stability of superhydrophobic surfaces holds immense significance in reducing both energy consumption and environmental pollution caused by friction drag. Based on the properties of mathematical discretization and the contact angle hysteresis generated by the wettability difference, a surface coupled with a wettability difference treatment and a convex-stripe array is developed by laser engraving and fluorine modification, and its performance in improving the air layer stability is experimentally studied in a von Kármán swirling flow field. The results show that the destabilization of the air layer is mainly caused by the Kelvin-Helmholtz instability, which is triggered by the density difference between gas and liquid, as well as the tangential velocity difference between gas and liquid. When the air layer is relatively thin, tangential wave destabilization occurs, whereas for larger thicknesses, the destabilization mode is coupled wave destabilization. The maximum Reynolds number that keeps the air layer fully covering the surface of the rotating disk (with drag reduction performance) during the disk rotation process is defined as the critical Reynolds number (Rec), which is 1.62 × 10[5] for the uniform superhydrophobic surface and 3.24 × 10[5] for the superhydrophobic surface with a convex stripe on the outermost ring (SCSSP). Individual treatments of wettability difference and a convex-stripe array on the SCSSP further improve the air layer stability, but Rec remains at 3.24 × 10[5]. Finally, the coupling of the wettability difference treatment with a convex-stripe array significantly improves the air layer stability, resulting in an increase of Rec to 4.05 × 10[5], and the drag reduction rate stably maintained around 30%.},
}
RevDate: 2024-02-20
Wavelength-induced shedding frequency modulation of seal whisker inspired cylinders.
Bioinspiration & biomimetics [Epub ahead of print].
The spanwise undulated cylinder geometry inspired by seal whiskers has been shown to alter shedding frequency and reduce fluid forces significantly compared to smooth cylindrical geometry. Undulation wavelength is systematically investigated in order to explore its effect on unsteady lift force and shedding frequency. Prior research has parameterized the whisker-inspired geometry and demonstrated the relevance of geometric variations on force reduction properties. Among the geometric parameters, undulation wavelength was identified as a significant contributor to forcing changes. To analyze the effect of undulation wavelength, a thorough investigation isolating changes in wavelength is performed to expand upon previous research that parameterized whisker-inspired geometry and the relevance of geometric variations on the force reduction properties. A set of five whisker-inspired models of varying wavelength are computationally simulated at a Reynolds number of 250 and compared with an equivalent aspect ratio smooth elliptical cylinder. Above a critical nondimensional value, the undulation wavelength reduces the amplitude and frequency of vortex shedding accompanied by a reduction in oscillating lift force. Frequency shedding is tied to the creation of wavelength-dependent vortex structures which vary across the whisker span. These vortices produce distinct shedding modes in which the frequency and phase of downstream structures interact to decrease the oscillating lift forces on the whisker model with particular effectiveness around the wavelength values typically found in nature. The culmination of the these location-based modes produces a complex and spanwise dependent lift frequency spectra at those wavelengths exhibiting maximum force reduction. Understanding the mechanisms of unsteady force reduction and the application of this geometry to vibration tuning and passive flow control for vortex-induced vibration (VIV) reduction.
Additional Links: PMID-38377615
Publisher:
PubMed:
Citation:
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@article {pmid38377615,
year = {2024},
author = {Dunt, T and Heck, KS and Lyons, K and Murphy, CT and Cal, RB and Franck, JA},
title = {Wavelength-induced shedding frequency modulation of seal whisker inspired cylinders.},
journal = {Bioinspiration & biomimetics},
volume = {},
number = {},
pages = {},
doi = {10.1088/1748-3190/ad2b04},
pmid = {38377615},
issn = {1748-3190},
abstract = {The spanwise undulated cylinder geometry inspired by seal whiskers has been shown to alter shedding frequency and reduce fluid forces significantly compared to smooth cylindrical geometry. Undulation wavelength is systematically investigated in order to explore its effect on unsteady lift force and shedding frequency. Prior research has parameterized the whisker-inspired geometry and demonstrated the relevance of geometric variations on force reduction properties. Among the geometric parameters, undulation wavelength was identified as a significant contributor to forcing changes. To analyze the effect of undulation wavelength, a thorough investigation isolating changes in wavelength is performed to expand upon previous research that parameterized whisker-inspired geometry and the relevance of geometric variations on the force reduction properties. A set of five whisker-inspired models of varying wavelength are computationally simulated at a Reynolds number of 250 and compared with an equivalent aspect ratio smooth elliptical cylinder. Above a critical nondimensional value, the undulation wavelength reduces the amplitude and frequency of vortex shedding accompanied by a reduction in oscillating lift force. Frequency shedding is tied to the creation of wavelength-dependent vortex structures which vary across the whisker span. These vortices produce distinct shedding modes in which the frequency and phase of downstream structures interact to decrease the oscillating lift forces on the whisker model with particular effectiveness around the wavelength values typically found in nature. The culmination of the these location-based modes produces a complex and spanwise dependent lift frequency spectra at those wavelengths exhibiting maximum force reduction. Understanding the mechanisms of unsteady force reduction and the application of this geometry to vibration tuning and passive flow control for vortex-induced vibration (VIV) reduction.},
}
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