European Journal of Mechanics B-fluids最新文献

{"title":"Study of the motion and interaction of micro-swimmers with different scales in Poiseuille flow","authors":"Tingting Qi (亓婷婷) ,&nbsp;Jianzhong Lin (林建忠) ,&nbsp;Zhenyu Ouyang (欧阳振宇)","doi":"10.1016/j.euromechflu.2024.11.001","DOIUrl":"10.1016/j.euromechflu.2024.11.001","url":null,"abstract":"<div><div>We conducted numerical simulations using the immersed boundary–lattice Boltzmann method to investigate the motion and interaction of microswimmers of different scales in Poiseuille flow. The squirmers self-propelling via generating surface waves were used as the model for microswimmers. The movement of two squirmers with different scale ratios (0.6–1.5), swimming Reynolds numbers (0.1–2.0), swimming strength (1–7), and blockage ratios (0.125–0.25) in Poiseuille flow was studied. Five classical motion patterns were identified: periodic tumbling, steady motion, periodic oscillation, damped oscillation, and chaotic motion modes. Initially, we examined the interaction between a pair of squirmers of the same scale and elucidated the causes of their different motion pattern transitions using the pressure distribution, direction angle, and swimming velocity of the squirmers. We investigated the variation of transport velocity with blockage ratio and swimming strength. A pair of squirmers with small ratios tended to migrate in a stable motion pattern, while those with large ratios showed a high tendency to change their motion patterns. Pushers with an increasing swimming Reynolds number were adsorbed to the wall and migrated stably along the wall.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 324-343"},"PeriodicalIF":2.5,"publicationDate":"2024-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142592940","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Vertical concentration distribution of fine settling particles in a pulsatile laminar open channel flow","authors":"Subham Dhar ,&nbsp;Nanda Poddar ,&nbsp;Kajal Kumar Mondal","doi":"10.1016/j.euromechflu.2024.10.015","DOIUrl":"10.1016/j.euromechflu.2024.10.015","url":null,"abstract":"<div><div>Sedimentation in river and drainage systems frequently increases flood risks, making the study of particle dispersion crucial for effective flood damage control. In the present research, the transport of fine settling particles in a laminar, periodic flow through an open channel is analytically investigated using the multi-scale homogenization method. To investigate how settling velocity affects the dispersion process of fine particles in a tidal wetland, Dhar et al. (2022) studied the dispersion coefficient and mean concentration of the settling particles applying the method of moments. The mean and transverse real concentration distributions of settling particles are analytically derived from the governing equation, and the influence of settling velocity, oscillation Reynolds number, and Schmidt number on the dispersivity and concentration profile of the settling particles is investigated. The results show a vertical non-uniformity of longitudinal concentration distribution due to the introduction of settling velocity. It is also observed that the sedimentation effect for purely oscillatory flow is negligibly small compared to that of the steady and oscillatory flow with a nonzero mean. Pulsatile behavior is observed in the difference rate profile between Taylor’s mean and present mean concentration. The study sheds light on the behavior of settling particles and can be useful for understanding sedimentation and wastewater treatment processes.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 309-323"},"PeriodicalIF":2.5,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142587180","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fully developed flow of a higher-gradient nanofluid in a vertical channel: Mixed and natural convection","authors":"A. Borrelli ,&nbsp;G. Giantesio ,&nbsp;M.C. Patria","doi":"10.1016/j.euromechflu.2024.10.013","DOIUrl":"10.1016/j.euromechflu.2024.10.013","url":null,"abstract":"<div><div>In the present work, we study the steady Poiseuille flow and heat transfer of a viscous fluid containing nano-sized particles in a vertical channel. The two walls of the infinitely long channel are kept at different constant temperatures. Particles and fluid may have different densities, and account is taken of the thermal expansivity of the fluid by invoking the Boussinesq approximation.</div><div>The momentum equation describing the fluid differs from the Navier–Stokes equations by containing a bi-Laplacian term of the velocity, as proposed by Fried and Gurtin. The higher-order terms in the momentum equation require additional boundary conditions (strong, weak, general adherence). Several velocity profiles are presented also for real nanofluid suspensions. The found velocities are compared with the velocity of nanofluids relative to the Buongiorno model.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 344-353"},"PeriodicalIF":2.5,"publicationDate":"2024-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142652473","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Annular Newtonian Poiseuille flow with pressure-dependent wall slip","authors":"Kostas D. Housiadas ,&nbsp;Evgenios Gryparis ,&nbsp;Georgios C. Georgiou","doi":"10.1016/j.euromechflu.2024.10.012","DOIUrl":"10.1016/j.euromechflu.2024.10.012","url":null,"abstract":"<div><div>We investigate the effect of pressure-dependent wall slip on the steady Newtonian annular Poiseuille flow employing Navier’s slip law with a slip parameter that varies exponentially with pressure. The dimensionless governing equations and accompanying auxiliary conditions are solved analytically up to second order by implementing a regular perturbation scheme in terms of the small dimensionless pressure-dependence slip parameter. An explicit formula for the average pressure drop, required to maintain a constant volumetric flowrate, is also derived. This is suitably post-processed by applying a convergence acceleration technique to increase the accuracy of the original perturbation series. The effects of pressure-dependent wall slip are more pronounced when wall slip is weak. However, as the slip coefficient increases, these effects are moderated and eventually eliminated as the perfect slip case is approached. The results show that the average pressure drop remains practically constant until the Reynolds number becomes sufficiently large. It is worth noting that all phenomena associated with pressure-dependent wall slip are amplified as the annular gap is reduced.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 299-308"},"PeriodicalIF":2.5,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142587179","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A two-dimensional numerical characterization on the droplet dynamics in the electric field by VOSET method","authors":"Yanning Wang ,&nbsp;Na Zhou ,&nbsp;Peng Yu ,&nbsp;Hong Lu ,&nbsp;Lin Miao ,&nbsp;Xiaoyan Chen ,&nbsp;Dongliang Sun","doi":"10.1016/j.euromechflu.2024.10.014","DOIUrl":"10.1016/j.euromechflu.2024.10.014","url":null,"abstract":"<div><div>A coupled volume-of-fluid and level set (VOSET) model is extended to the simulation of electro-hydrodynamic (EHD) flow. The good accuracy of proposed model is validated by comparing with previous results. Although the electrostrictive force might be greater than the Coulomb and dielectric forces under certain conditions, it has no influence on droplet dynamic behaviors except the pressure distribution. The electro-coalescence of droplet pair is systematically investigated. In addition to the coalescence and repulsion, two droplets might neither coalesce nor repulse with the repulsive hydrodynamic force and attractive electric force strike a balance. The electro-coalescence of two droplets always happens as long as the electric conductivity ratio is smaller than the permittivity ratio. The critical permittivity ratio separating the coalescence and repulsion of droplets increases as the increase of electric conductivity ratio. The electro-coalescence time of two droplets decreases as the permittivity ratio and electric capillary number increase. Nevertheless, the electro-coalescence time shows different variation tendency as the increase of electric conductivity ratio with different permittivity ratios and electric capillary numbers.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 284-298"},"PeriodicalIF":2.5,"publicationDate":"2024-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142551889","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Coating flow of a liquid film with colloidal particles on a vertical fiber","authors":"Garima Singh,&nbsp;Naveen Tiwari","doi":"10.1016/j.euromechflu.2024.10.009","DOIUrl":"10.1016/j.euromechflu.2024.10.009","url":null,"abstract":"<div><div>A thin liquid film of colloidal suspension is considered which is spreading down on a vertical cylinder under the effect of gravity. A precursor film model is employed at the three-phase contact line to relieve the stress singularity. The curvature pressure leads to the formation of a capillary ridge at the contact-line. Bulk and surface colloids are assumed to be present in the liquid film. The interfacial pattern is governed by the film evolution equation, obtained by simplifying mass and momentum balance equations within the lubrication assumption, while rapid vertical diffusion is assumed for the advection–diffusion equation of the bulk concentration. Fluid viscosity and diffusivity are considered to be functions of the particle volume fraction. The effects of the bulk and surface colloids on the spreading film dynamics are systematically studied. The presence of bulk colloids leads to the thinning of the capillary ridge for smaller inlet bulk colloid concentrations. On the other hand, a larger inlet bulk concentration leads to the formation of a secondary advancing front behind the capillary ridge in the film profile. A reduced contact point velocity is observed with an increase in the upstream bulk concentration. Surface concentration is found to result in a hump-like structure behind the capillary ridge in the upstream direction due to solutal Marangoni stress. The Marangoni stress also hinders the surface-tension-driven spreading, resulting in a smaller contact line velocity. Reducing the Bond number results in unstable film profiles, which lead to a wave-like structure in the region with no bulk concentration gradients.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 271-283"},"PeriodicalIF":2.5,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142536098","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of offset jet width on periodic flow in a dual jet","authors":"Tanmoy Mondal","doi":"10.1016/j.euromechflu.2024.10.005","DOIUrl":"10.1016/j.euromechflu.2024.10.005","url":null,"abstract":"<div><div>The primary aim of this work is to investigate the impact of the offset jet width on the unsteady flow characteristics of a turbulent dual jet, which consists of a wall jet and an offset jet. A computational fluid dynamics code is developed to solve the unsteady Reynolds-averaged Navier–Stokes (URANS) equations. The width of the offset jet is varied while keeping the width of the wall jet constant at the separation distance between the two jets. When the ratio of the offset jet width (<span><math><mi>w</mi></math></span>) to the separation distance (<span><math><mi>d</mi></math></span>) is <span><math><mrow><mi>w</mi><mo>/</mo><mi>d</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>5</mn></mrow></math></span>, the flow field exhibits a periodic vortex shedding phenomenon. Conversely, when <span><math><mrow><mi>w</mi><mo>/</mo><mi>d</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>4</mn></mrow></math></span>, the flow field remains steady. The shedding phenomenon is discernible even when <span><math><mrow><mi>w</mi><mo>/</mo><mi>d</mi><mo>=</mo><mn>2</mn></mrow></math></span>. The instantaneous velocity components display sinusoidal oscillations at <span><math><mrow><mn>0</mn><mo>.</mo><mn>5</mn><mo>≤</mo><mi>w</mi><mo>/</mo><mi>d</mi><mo>≤</mo><mn>2</mn></mrow></math></span>. Applying the fast Fourier transform to these sinusoidal signals yields a distinct frequency peak at the vortex shedding frequency. Within the range of <span><math><mrow><mn>0</mn><mo>.</mo><mn>5</mn><mo>≤</mo><mi>w</mi><mo>/</mo><mi>d</mi><mo>≤</mo><mn>2</mn></mrow></math></span>, the shedding frequency decreases as the width of the offset jet increases. This trend continues until it reaches a constant value at <span><math><mrow><mi>w</mi><mo>/</mo><mi>d</mi><mo>=</mo><mn>1</mn><mo>.</mo><mn>4</mn></mrow></math></span>. This indicates that the width of the offset jet has a notable influence on the shedding phenomenon within the range of <span><math><mrow><mn>0</mn><mo>.</mo><mn>5</mn><mo>≤</mo><mi>w</mi><mo>/</mo><mi>d</mi><mo>≤</mo><mn>1</mn><mo>.</mo><mn>4</mn></mrow></math></span>. For <span><math><mrow><mn>1</mn><mo>.</mo><mn>4</mn><mo>&lt;</mo><mi>w</mi><mo>/</mo><mi>d</mi><mo>≤</mo><mn>2</mn></mrow></math></span>, the shedding frequency remains unaffected by the offset jet width variation. Depending on the value of <span><math><mrow><mi>w</mi><mo>/</mo><mi>d</mi></mrow></math></span>, the shedding phenomenon is characterized by three flow regimes: a steady flow regime (for<span><math><mrow><mi>w</mi><mo>/</mo><mi>d</mi><mo>≤</mo><mn>0</mn><mo>.</mo><mn>4</mn></mrow></math></span>), an outer share layer-influenced shedding regime (for <span><math><mrow><mi>w</mi><mo>/</mo><mi>d</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>5</mn><mo>−</mo><mn>1</mn><mo>.</mo><mn>4</mn></mrow></math></span>), and an outer shear layer-free shedding regime (for <span><math><mrow><mi>w</mi><mo>/</mo><mi>d</mi><mo>&gt;</mo><mn>1</mn><mo>.</mo><mn>4</mn></mrow></math></span>).</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 253-270"},"PeriodicalIF":2.5,"publicationDate":"2024-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142536099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Surface wave damping by a Robin boundary condition at a permeable seabed","authors":"Jan Erik H. Weber","doi":"10.1016/j.euromechflu.2024.10.010","DOIUrl":"10.1016/j.euromechflu.2024.10.010","url":null,"abstract":"<div><div>We investigate the damping of inviscid surface gravity waves when they propagate over a permeable seabed. Traditionally, this problem is solved by considering the wave motion in the upper water layer interacting with the Darcy flow in the porous bottom layer through matching of the solutions at the permeable interface. The novel approach in this study is that we describe the interaction between the upper fluid layer and the permeable bottom layer by the application of a Robin boundary condition. By varying the magnitude of the Robin parameter <span><math><mi>R</mi></math></span>, we can model the bottom structure of the fluid layer from rigid to completely permeable. In the case when the bottom is a porous medium where Darcy’s law applies, or composed by densely packed vertical Hele-Shaw cells, <span><math><mi>R</mi></math></span> is small, and can by determined by comparison with analytical results for a two-layer structure. In this case the wave damping is small. For larger values of <span><math><mi>R</mi></math></span>, the damping increases, and for very large <span><math><mi>R</mi></math></span>, the wave is almost critically damped. For the nonlinear transport in spatially damped shallow-water waves, increasing bottom permeability (larger <span><math><mi>R</mi></math></span>), reduces the magnitude of the horizontal Stokes drift velocity, while the drift profile tends to become parabolic with height. The vertical Stokes drift in the limit of large permeability is linear with height, with a magnitude that is larger than the horizontal drift. It is suggested that the implementation of a permeable bottom bed in some cases could prevent shorelines from damaging erosion by incoming surface waves.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 243-252"},"PeriodicalIF":2.5,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142536096","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exploring the influence of flexibility on rotor performance in turbulent flow environments","authors":"Marwa Fakhfekh ,&nbsp;Wael Ben Amira ,&nbsp;Malek Abid ,&nbsp;Aref Maalej","doi":"10.1016/j.euromechflu.2024.10.002","DOIUrl":"10.1016/j.euromechflu.2024.10.002","url":null,"abstract":"<div><div>Flexibility plays a crucial role in the design and performance of modern rotors. Its impact on rotor performance and its ability to adapt to external flow disturbances are well-established. In this study, we employ numerical simulations to explore the behavior of a flexible rotor submerged in a turbulent flow, aiming to forecast the influence of its flexibility on performance metrics. The rotational motion of the rotor and the forces imposed by the flow induce deformations in the blades, including bending and twisting. These deformations not only disrupt the flow patterns (vortices) in the turbulent wake but also modify the aerodynamic profiles, thereby affecting essential performance aspects such as thrust, drag, and lift. Our objective is to uncover the relationships between blade deformations, rotation frequencies, and rotor performance in a turbulent flow with a Reynolds number, <span><math><mrow><mi>R</mi><mi>e</mi><mo>=</mo><mi>O</mi><mrow><mo>(</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>4</mn></mrow></msup><mo>)</mo></mrow></mrow></math></span>, and for a tip speed ratio in the range <span><math><mrow><mo>[</mo><mn>0</mn><mo>,</mo><mn>18</mn><mo>]</mo></mrow></math></span>. We demonstrate that the mean blade bending angle can be effectively expressed using a modified Cauchy number, revealing a scaling law. We also examined how the aerodynamic performance of the rotor blade is affected by variations in the tip speed ratio, either amplifying or reducing it. Through this research, we advance our understanding of the interplay between rotor flexibility, deformation, and performance, contributing to the optimization of rotor design and operational efficiency.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 199-212"},"PeriodicalIF":2.5,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142536092","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A novel transformation free nonuniform higher order compact finite difference scheme for solving incompressible flows on circular geometries","authors":"Swapan K. Pandit,&nbsp;Pradip Das","doi":"10.1016/j.euromechflu.2024.10.004","DOIUrl":"10.1016/j.euromechflu.2024.10.004","url":null,"abstract":"<div><div>This paper presents a newly developed higher order compact scheme that is designed on a polar grid by using an implicit form of first order derivatives on nonuniform grids. These derivatives are formulated compactly and implicitly with a relationship of the coefficients in terms of the unknown variables. The proposed scheme is free from transformation technique and third order accurate in space. The objective is to solve Stokes equations and Navier–Stokes equations on curvilinear grids using the polar nature of the coordinate system. Our newly developed scheme is used to solve several problems namely, a problem having an analytical solution, Stokes flow with different orientations of the lids for the half filled annular and wedge cavity, the lid driven polar cavity flow and flow past an impulsively started circular cylinder. Our newly developed scheme is used to analyze the flow structures for the flow governed by different physical control parameters: the cavity radius ratio, the cavity angle and the ratio of the upper and lower lid speeds with rotating coaxial cylinders and Reynolds number for the impulsively started circular cylinder. The Stokes equations and the Navier–Stokes equations are efficiently solved with Dirichlet as well as Neumann boundary conditions. The efficacy and robustness of our proposed scheme are shown through its applicability in all the complex fluid flow problems.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 225-242"},"PeriodicalIF":2.5,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142536095","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}