European Journal of Mechanics B-fluids最新文献

{"title":"Reconstruction of unstable atmospheric surface layer streamwise turbulence based on multi-layer perceptron neural network architecture","authors":"Chentao Huang ,&nbsp;Yinhua Ma ,&nbsp;Yuye Wang ,&nbsp;Li Liu ,&nbsp;Ao Mei","doi":"10.1016/j.euromechflu.2024.11.006","DOIUrl":"10.1016/j.euromechflu.2024.11.006","url":null,"abstract":"<div><div>The accurate simulation of sand-laden turbulence under different stratification stabilities remains a critical challenge in turbulence research. This study presents an innovative approach to reconstructing streamwise turbulence in an unstable atmospheric surface layer (ASL) using a multi-layer perceptron (MLP) neural network architecture. Leveraging high-resolution measurements of three-dimensional wind velocity and temperature from multiple observational sites, the study develops prediction models for streamwise wind velocity at varying heights in the unstable ASL. The predictive model integrates large-scale motions (LSMs) generated by the MLP, small-scale motions (SSMs) derived from the Kaimal spectrum, and mean wind velocity, providing a comprehensive representation of turbulence. The impact of sand content and stratification stability on model performance is analyzed, with discussion highlighting the model's strengths and limitations under weak instability conditions. Validation is conducted through cross-site comparison, statistical analysis, and power spectrum assessment, demonstrating the model's ability to capture the temporal and spectral characteristics of wind velocity in sand-laden, unstable ASL conditions. The study also reveals that, under weak instability, shear forces dominate the formation of coherent structures, while buoyancy effects enhance vertical mixing as instability increases. Compared to existing models, the proposed prediction model is applicable over a broader range of conditions, offering a valuable data source for the study of atmospheric sand-laden turbulence and serving as a reference for practical sand control projects.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 392-413"},"PeriodicalIF":2.5,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142702764","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":"Instability in heated water-porous system","authors":"Shuai Wang ,&nbsp;Zhen Ouyang ,&nbsp;Qiang Yang ,&nbsp;Zijing Ding","doi":"10.1016/j.euromechflu.2024.11.003","DOIUrl":"10.1016/j.euromechflu.2024.11.003","url":null,"abstract":"<div><div>This paper investigates the stability in a heated fluid-porous system. Darcy’s law is used for the flow in the porous medium. Previous studies indicate that the classical Rayleigh–Bénard instability in this flow is independent of the mutual positions of the fluid layer and porous layer. This paper demonstrates that the instability depends on the mutual positions of the fluid layer and porous layer when the liquid density is nonlinearly dependent on temperature. When porous medium is located at the bottom of the system, onset of convection may occur in lower porous layer (pure-porous mode), upper water layer (pure-water mode) or across both layers (porous-water mode). However, onset of convection cannot take place only in the upper porous layer when porous medium is placed at the top of the system. The influence of depth ratio <span><math><mover><mrow><mi>d</mi></mrow><mrow><mo>ˆ</mo></mrow></mover></math></span> and the density inversion parameter <span><math><msub><mrow><mi>θ</mi></mrow><mrow><mi>M</mi></mrow></msub></math></span> on instability of bilayer system are investigated in detail and dependence of critical modes on parameters are summarized in phase diagrams. In addition, direct numerical simulation is used to analyse the instability mechanism and identify subcritical or supercritical instability for bilayer systems.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 428-439"},"PeriodicalIF":2.5,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142702766","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":"Viscous fingering analysis for water-drive oil in the inclined plane","authors":"Menghan Zhang ,&nbsp;Lu Jiang ,&nbsp;Zewen Gu ,&nbsp;Chicheng Ma ,&nbsp;Yuting Wu ,&nbsp;Jianlin Liu","doi":"10.1016/j.euromechflu.2024.11.005","DOIUrl":"10.1016/j.euromechflu.2024.11.005","url":null,"abstract":"<div><div>Viscous fingering is a common instability event that occurs during the process of water-drive oil for oil recovery, significantly limiting the efficiency of oil extraction. In this study, we propose a film flow model that accounts for the variation in height at the water-oil two phase interface, enabling the calculation and analysis of the triggering mechanism and flow evolution process of this unstable phenomenon. We theoretically derive the equation of water film flow, which can be used to explore the flow evolution of the two-phase interface in the process of oil displacement. By numerically solving the two-dimensional flow equation, we obtain the traveling wave profile and find that the morphology of the two-phase interface is significantly affected by the plane’s inclined angle, capillary number and density ratio of the two-phase liquid. Furthermore, we perform linear stability analysis and finite element numerical simulation considering small initial disturbances to explore the triggering conditions of viscous fingering phenomenon and the full time from gentle displacement to unstable flow. The results reveal that the moving contact line of the driven liquid front is more stable when the viscosity of the oil is less different from the driven liquid and has a smaller density, thereby improving of the driving efficiency in the water-driven oil process. These insights have significant implications for guiding efforts to enhance oil recovery efficiency, and we provide concrete engineering suggestions to achieve this aim.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 414-427"},"PeriodicalIF":2.5,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142702765","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":"Influence of structural parameters on the performance of fluid oscillators","authors":"Wenhui Zhai ,&nbsp;Yuxin Fan","doi":"10.1016/j.euromechflu.2024.11.002","DOIUrl":"10.1016/j.euromechflu.2024.11.002","url":null,"abstract":"<div><div>The fluid oscillator, relying on the Coanda effect, is a flow control device that can alter the direction or velocity of a jet both spatially and temporally. The fuel injection device based on a fluid oscillator significantly enhances atomization and spatial dispersion performance compared to a direct-spray nozzle. However, when used in high heat load afterburners with aviation kerosene as the working medium, oxidative coking issues may arise. To address this, it is recommended to use premixed rich fuel-vapor as the working fluid in order to reduce the residence time of fuel in the oscillator. This study investigates the flow rate and frequency variation of ideal air (simulated gas phase fuel) as it moves through a double feedback channel fluid oscillator with varying thicknesses and outlet throat widths. Experimental and numerical simulation methods are employed. And the influence mechanism is analyzed through an examination of the flow field structure within the cavity of the fluid oscillator. The results indicate that increasing the thickness of the fluid oscillator leads to a higher outlet tangential velocity and deflection angle, while simultaneously decreasing the oscillation frequency. Conversely, widening the fluid oscillator throat results in a decrease in tangential velocity, deflection angle, and oscillation frequency. The performance of the fluid oscillator reaches a critical threshold when the outlet throat is square. As thickness increases, the rate of decrease in oscillation frequency and the rate of increase in tangential velocity both slow down. Furthermore, the maximum deflection angle of the airflow at the oscillator outlet reaches a critical value at a thickness of 3.375 mm, beyond which the trend of increasing deflection angle also slows. When the thickness of the oscillator is less than 3.375 mm, mass flow is the predominant driving factor for airflow deflection in the mixing chamber. In contrast, when the thickness is greater than or equal to 3.375 mm, pressure becomes the primary driving factor for this deflection.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 367-377"},"PeriodicalIF":2.5,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142652471","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":"Prediction of wind loading on masked angle members in lattice tower structures","authors":"A. Hadane ,&nbsp;V. Laurent ,&nbsp;J.A. Redford ,&nbsp;M. Gueguin ,&nbsp;F. Hafid ,&nbsp;J.-M. Ghidaglia","doi":"10.1016/j.euromechflu.2024.10.008","DOIUrl":"10.1016/j.euromechflu.2024.10.008","url":null,"abstract":"<div><div>Quantification of the wind loading is critical in lattice tower structure engineering. In this study, we use Computational Fluid Dynamics (CFD) to investigate the aerodynamic loading on two angle members of a lattice tower structure. The presence of two bluff bodies means that one of the angle members may be masked by the other and will thus undergo less wind loading, which is called the mask effect. In the current work, we were specifically interested in investigating this effect with respect to the angles of attack of the two angle members along with the inline and normal separation distance. The four parameters yield a large parameter space which is best tackled using a sophisticated sampling method such as Latin hypercube sampling. First, we validated our RANS simulation results against experiments and Large Eddy Simulation (LES). Then, we performed two-dimensional simulations on a large range of configurations to underline the impact of the input parameters on the output variables, which are the drag and lift coefficients. To produce a tool that can be applied by a structural engineer, the database created using the time-consuming CFD simulations was used to create a correlation between the input parameters and output variables. The functions used in the correlations were designed to respect the symmetries and limiting behavior in the problem. We then investigated the performance of four different cross-validated regression models to predict the drag and lift coefficients. Once created, the regression models produce a method that does not require CFD simulations to be run. The models’ accuracy represents a significant improvement in predicting wind loads on lattice towers. While further refinement is possible, the current results provide a solid basis for engineering design purposes.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 378-391"},"PeriodicalIF":2.5,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142652472","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":"Turbulent spiral flow of power-law fluid in annular channel","authors":"Yaroslav Ignatenko ,&nbsp;Andrey Gavrilov ,&nbsp;Oleg B. Bocharov ,&nbsp;Roger Aragall","doi":"10.1016/j.euromechflu.2024.10.016","DOIUrl":"10.1016/j.euromechflu.2024.10.016","url":null,"abstract":"<div><div>Transient three-dimensional numerical simulations of power-law fluid flow in an annular channel with a diameter ratio of 1/2 were performed. The outcomes of the simulations using the URANS approach were contrasted with the results of the RANS and LES approaches for Newtonian and power-law fluids. It was demonstrated that comparable outcomes to those obtained through LES can be achieved through URANS with a reduced computational cost. It was determined that the RANS approach tends to underestimate turbulent kinetic energy and pressure losses. Parametric studies were conducted using the URANS approach, encompassing a range of Reynolds numbers (<span><math><mrow><mi>R</mi><mi>e</mi></mrow></math></span>) between 100 and 10,000, dimensionless rotation rates (<span><math><mi>N</mi></math></span>) values between 0.2 and 5, and power-law indices (<span><math><mi>n</mi></math></span>) between 0.4 and 1. The following flow regimes were identified: (1) flow without vortices; (2) Taylor-type toroidal vortices; (3) Görtler-type continuous spiral vortices swirling around the inner cylinder; and (4) small-scale Görtler-type vortices near both channel walls. The numerical experiments demonstrated that the rotation of the inner cylinder resulted in three notable effects: a reduction in the apparent viscosity within the vicinity of the rotating cylinder, a decline in viscous shear stresses, and the development of Görtler-type vortex structures, which contributed to an increase in energy losses. Additionally, at Reynolds numbers below 300, high rotation led to the formation of Taylor-type vortices and a reduction in pressure losses. The power law fluid requires increased rotation of the inner cylinder to form vortices and transition the flow to turbulent. When the Reynolds number is less than 300, the first mechanism is the dominant factor, resulting in a reduction in pressure loss. At Reynolds numbers of approximately 300, the first two mechanisms are in competition, with the pressure loss dependent on the power law index, <span><math><mi>n</mi></math></span>. Finally, at Reynolds numbers greater than 300, secondary vortex structures, such as Görtler vortices, become the dominant factor, leading to an increase in pressure loss with rotation.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 354-366"},"PeriodicalIF":2.5,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142652474","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":"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}