European Journal of Mechanics B-fluids最新文献

Influence of slip-yield stress model on the oscillatory squeeze flow of a viscoelastic fluid confined between two spheres 滑移-屈服应力模型对两球间粘弹性流体振荡挤压流动的影响

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2026-01-13 DOI: 10.1016/j.euromechflu.2026.204466

D. Matuz , F. Méndez , J. Arcos , O. Bautista , R. Baños

In this study, we examine the oscillatory squeeze flow of a viscoelastic fluid confined between two hydrophobic spheres of differing radii. The fluid flow is generated by the harmonic motion of an upper sphere, while the lower sphere remains stationary. We have considered that the gap between the spheres is much smaller than their radii and that the oscillation amplitude of the moving sphere is small compared to this gap. Under these conditions, the curved surfaces can be approximated by quadratic functions of the radial coordinate

r

. A dynamic slip law is used to model slippage at the fluid–solid interface, which incorporates interfacial memory effects through the slip-relaxation time, together with the slip-yield Spikes–Granick condition, in which interfacial slippage arises when the fluid shear stress exceeds a critical value; otherwise, a non-slip region persists. Given the dominance of viscous over inertial effects, the convective terms in the momentum equation were neglected, and the analysis was carried out in a strictly periodic regimen. An analytical solution of the governing equations is derived, where the following parameters control the phenomenon: the Deborah number

De

, the Womersley number

α

, the Navier slip length

\tilde{λ}

, the slip relaxation number

{De}_{s}

and the critical shear stress at the fluid–solid interface

{\tilde{τ}}_{c}

. Our findings indicate that, relative to flat surfaces, when curved surfaces are assumed, the zone of the non-slip region decreases. Additionally, incorporating viscoelastic fluids results in a diminished compression force, and lower mechanical power is consumed by implementing hydrophobic surfaces, high oscillation frequencies, and viscoelastic fluids.

在这项研究中，我们研究了粘弹性流体在两个不同半径的疏水球体之间的振荡挤压流动。流体流动是由上球的调和运动产生的，而下球保持静止。我们已经考虑到球体之间的间隙比它们的半径小得多，并且与这个间隙相比，运动球体的振荡幅度很小。在这些条件下，曲面可以用径向坐标r的二次函数来近似。采用动态滑移定律来模拟流固界面的滑移，其中通过滑移松弛时间考虑了界面记忆效应，以及滑移屈服尖峰-格兰尼克条件，在该条件下，当流体剪切应力超过临界值时，界面发生滑移；否则，一个防滑区域将持续存在。考虑到粘性效应优于惯性效应，动量方程中的对流项被忽略，并在严格的周期方案中进行分析。导出了控制方程的解析解，其中以下参数控制该现象：Deborah数De、Womersley数α、Navier滑移长度λ λ、滑移松弛数Des和流固界面处的临界剪切应力τ τ c。我们的研究结果表明，相对于平面，当假设曲面时，防滑区区域减小。此外，粘弹性流体的加入减少了压缩力，并且通过疏水表面、高振荡频率和粘弹性流体消耗的机械功率更低。

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引用次数: 0

Influence of front airfoil leading-edge serrations on turbulence interaction noise characteristics of tandem airfoils at different angles of attack 前翼型前缘锯齿对不同迎角下串列翼型湍流相互作用噪声特性的影响

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2026-01-08 DOI: 10.1016/j.euromechflu.2026.204463

Xishuai Yu, Jianxi Zhou, Yong Li

This study investigates the effectiveness of leading-edge serrations as a passive noise control strategy for tandem airfoils across different angles of attack. Far-field noise measurements indicate that applying leading-edge serrations to the front airfoil significantly reduces wake turbulence interaction noise at 5° and 10° angles of attack; however, the reduction effect weakens as the angle of attack increases. At an angle of attack of 17°, the leading-edge serrations no longer reduce the peak wake turbulence interaction noise. Furthermore, neither the application of leading-edge serrations nor changes in the airfoil angle of attack affect the noise directivity. Flow field analyses based on Particle Image Velocimetry (PIV) reveal that the serrated leading edge markedly attenuates turbulence and vortex shedding in the wake of the front airfoil. Notably, as the angle of attack increases, the influence of vortex shedding and vortex–solid interference between the front and rear airfoils on the overall noise decreases. The intensity of the front airfoil wake turbulence and the extent of its interaction with the rear airfoil are identified as the dominant factors governing the interaction noise in tandem airfoils. Therefore, the application of leading-edge serrations in tandem airfoils is recommended only for low angles of attack. These findings may offer practical guidance for noise reduction in airfoil arrays of rotating machinery, such as guide vane rows, fan blade rows, and turbine blade rows.

本研究探讨了前缘锯齿作为一种被动噪声控制策略的有效性跨不同迎角串联式翼型。远场噪声测量表明，应用前缘锯齿到前翼型显著降低尾迹湍流相互作用噪声在5°和10°攻角；随着攻角的增大，减振效果逐渐减弱。当迎角为17°时，前缘锯齿不再降低尾迹湍流相互作用噪声峰值。此外，前缘锯齿的应用和翼型迎角的变化都不会影响噪声指向性。基于粒子图像测速（PIV）的流场分析表明，锯齿状前缘可以显著减弱前翼型尾迹中的湍流和旋涡脱落。值得注意的是，随着迎角的增大，旋涡脱落和前后翼型之间的涡固干涉对整体噪声的影响减小。确定了前翼型尾迹湍流的强度及其与后翼型相互作用的程度是控制串列型相互作用噪声的主要因素。因此，前缘锯齿在串联翼型的应用是建议只有低攻角。这些发现可以为旋转机械翼型阵列的降噪提供实用的指导，例如导叶排、风扇叶片排和涡轮叶片排。

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引用次数: 0

High-fidelity actuator line large eddy simulations of multi-turbine VAWT clusters under varying geometric configurations 不同几何构型下多涡轮VAWT簇的高保真作动器线大涡模拟

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2026-01-08 DOI: 10.1016/j.euromechflu.2026.204462

Prathamesh Banda, Mayank Verma , D.V.G. Prasad, Ashoke De

This study investigates the aerodynamic performance of VAWT clusters under varying array geometries. Staggered V-shaped clusters of vertical-axis wind turbines (VAWTs) are examined to assess aerodynamic interactions in compact wind farm layouts. Configurations use six UNH-RVAT reference turbines, with variations in cluster angle, streamwise spacing, and turbine count. High-fidelity actuator-line large-eddy simulations (LES) are performed using a modified Xcompact3D solver. A six-turbine cluster is analyzed for cluster angles of 20°, 30°, and 45° and streamwise spacings of 2D and 3D (two or three rotor diameters). Results are compared to a reduced five-turbine cluster. Cluster angle strongly affects wake overlap and power capture. At a narrow angle (20°), wake shielding is severe and downstream output is lowered, whereas a wide angle (45°) improves wake recovery but reduces upstream synergy. The intermediate angle (30°) yields the highest overall array performance by balancing these effects. Increased streamwise spacing (3D vs 2D) markedly enhances wake recovery and significantly raises downstream turbine efficiency. Reducing the turbine count from six to five further alleviates wake losses, resulting in higher average power coefficients and more uniform inflow. Flow-field diagnostics (velocity, vorticity, kinetic energy deficit) confirm these trends. These results provide design guidelines: optimizing cluster angle, spacing, and turbine count can substantially improve the efficiency and robustness of high-density VAWT arrays.

本文研究了不同阵列几何形状下VAWT簇的气动性能。研究了垂直轴风力涡轮机（VAWTs）的交错v形集群，以评估紧凑风电场布局中的气动相互作用。配置使用六个UNH-RVAT参考涡轮机，在集群角度，流向间距和涡轮机计数的变化。采用改进的Xcompact3D求解器进行了高保真作动线大涡模拟（LES）。对六涡轮集群进行了分析，集群角度为20°，30°和45°，流向间距为2D和3D（两个或三个转子直径）。结果与减少的五涡轮集群进行了比较。簇角对尾迹重叠和功率捕获有很大影响。在窄角（20°）时，尾流屏蔽严重，下游输出降低，而广角（45°）可以改善尾流恢复，但会降低上游协同。中间角度（30°）通过平衡这些影响产生最高的整体阵列性能。增加的流向间距（3D vs 2D）显著提高了尾迹恢复，并显著提高了下游涡轮效率。将涡轮数量从6台减少到5台进一步减轻了尾迹损失，从而提高了平均功率系数和更均匀的流入。流场诊断（速度、涡度、动能亏损）证实了这些趋势。这些结果为设计提供了指导：优化簇角、间距和涡轮数量可以大大提高高密度VAWT阵列的效率和鲁棒性。

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引用次数: 0

Visualising coherent vortices generated by a swimming dolphin 正在观察游泳的海豚所产生的连贯漩涡

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2026-01-07 DOI: 10.1016/j.euromechflu.2025.204452

Yutaro Motoori, Hideki Murahata, Susumu Goto

We visualise the hierarchy of coherent vortices generated by a freely swimming dolphin, obtained from direct numerical simulations at a high Reynolds number. The visualisations are based on isosurfaces of the second invariant of the velocity gradient tensor evaluated from scale-decomposed velocity fields. We describe in detail the scale-decomposition procedure and the polygon-based visualisation, which enables the rendering of the data despite their large size. We also emphasise that visualising the hierarchy of coherent vortices clarifies the physical mechanism of dolphin propulsion, and more generally, provides physical insight into turbulence around swimming and flying organisms.

在高雷诺数的直接数值模拟中，我们可视化了自由游泳的海豚产生的相干涡的层次结构。可视化是基于速度梯度张量的第二不变量的等值面，从尺度分解的速度场中评估。我们详细描述了尺度分解过程和基于多边形的可视化，这使得数据的渲染，尽管他们的大尺寸。我们还强调，可视化连贯漩涡的层次结构阐明了海豚推进的物理机制，更广泛地说，提供了对游泳和飞行生物周围湍流的物理见解。

引用次数: 0

On the local anisotropy of quasi-two-dimensional forced shallow flow: An experimental study 准二维强迫浅流的局部各向异性实验研究

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2026-01-02 DOI: 10.1016/j.euromechflu.2025.204453

G. Antar , J. El Kuweiss , K. Schneider , C. Habchi , S. Benkadda

We experimentally investigate quasi-two-dimensional (Q2D) forced shallow flows in the presence of solid boundaries and analyze the deviation from the Kolmogorov–Kraichnan (KK) theory. Complex motion is generated using a thin electrolyte subject to electromagnetic forces, and we employ particle tracking velocimetry to resolve the flow properties down to the Kolmogorov scale. Although the velocity probability distribution function closely resembles a Gaussian, deviations from Gaussianity emerge for velocity increments as scales decrease. The second-order structure function supports the onset of local anisotropy at small scales. The sign of the third-order structure function indicates the dominance of the inverse cascade in energy transfer, and the cross-correlation between longitudinal and transverse directions proves to be significant at large scales. The breakdown of local isotropy is consistent with the effect of bottom friction, which primarily affects the longitudinal motion, while leaving the perpendicular direction unaffected. This local anisotropy propagates to larger scales via the inverse energy cascade, with nonlinear interactions eventually influencing the perpendicular direction.

实验研究了固体边界存在下的准二维（Q2D）强迫浅层流动，并分析了与Kolmogorov-Kraichnan （KK）理论的偏差。使用受电磁力作用的薄电解质产生复杂的运动，我们使用粒子跟踪测速来解析流动特性到Kolmogorov尺度。虽然速度概率分布函数非常类似于高斯分布，但随着尺度的减小，速度增量会出现偏离高斯分布的情况。二阶结构函数支持小尺度下局部各向异性的发生。三阶结构函数的符号表明逆级联在能量传递中占主导地位，并且在大尺度上纵向和横向的相互关系显著。局部各向同性的破坏与底部摩擦的影响一致，主要影响纵向运动，而不影响垂直方向。这种局部各向异性通过逆能量级联传播到更大的尺度，非线性相互作用最终影响垂直方向。

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引用次数: 0

Thermophoresis of a spherical particle straddling a flat interface in a Brinkman medium at a 90° contact angle 在布林克曼介质中以90°接触角跨越平面界面的球形粒子的热泳动

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-12-30 DOI: 10.1016/j.euromechflu.2025.204441

M.S. Faltas , E.A. Ashmawy , Samar A. Mahrous , M. Magdy El Sayed , Kareem E. Ragab

This study investigates the quasi-steady axisymmetric thermophoretic motion of a spherical particle partially submerged at the flat interface of a semi-infinite Brinkman medium. The analysis is conducted under the assumptions of small Reynolds and Péclet numbers, while the capillary number is considered sufficiently small to preserve the flatness of the interface. The specific case of a

90 °

contact angle with the flat surface is examined. To avoid singularities at the contact line, the Knudsen number is assumed to lie within the slip-flow regime. Analytical expressions are derived for the thermophoretic velocity and force acting on the half-submerged particle. Graphical results illustrate the influence of parameters such as Fourier thermal conductivity ratio, Knudsen number, medium permeability, frictional slip, and thermal stress slip. Furthermore, the limiting behavior corresponding to thermophoresis in a classical viscous fluid is discussed. Since the present solution is exact, the case of a

90 °

contact angle also serves as a benchmark for validating numerical solutions at other contact angles. The findings are relevant to applications involving particle manipulation at fluid–porous interfaces, such as targeted drug delivery across biological membranes, pollutant transport at soil–air boundaries, and the design of microfluidic systems for controlled colloidal assembly.

本文研究了半无限布林克曼介质平面界面上部分浸没的球形粒子的准稳态轴对称热泳运动。分析是在小雷诺数和p克莱特数的假设下进行的，而毛细数被认为足够小以保持界面的平整度。研究了与平面形成90°接触角的具体情况。为了避免在接触线上出现奇点，假定克努森数位于滑流区。导出了热泳速度和作用在半浸没颗粒上的力的解析表达式。图形结果说明了傅立叶导热系数、克努森数、介质渗透率、摩擦滑移和热应力滑移等参数的影响。进一步讨论了经典粘性流体中热泳动的极限行为。由于目前的解是精确的，90°接触角的情况也可以作为验证其他接触角数值解的基准。这些发现与涉及流体-多孔界面的粒子操纵的应用相关，例如跨生物膜的靶向药物输送，土壤-空气边界的污染物输送，以及用于控制胶体组装的微流体系统的设计。

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引用次数: 0

Sensitivity analysis of Navier–Stokes equations with heat transfer using the first-order polynomial chaos method and FEV discretization 基于一阶多项式混沌法和FEV离散化的Navier-Stokes传热方程灵敏度分析

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-12-29 DOI: 10.1016/j.euromechflu.2025.204430

N. Nouaime , B. Després , M.A. Puscas , C. Fiorini

This paper uses the intrusive polynomial chaos method (IPCM) to analyze sensitivity in heat transfer problems governed by the Navier–Stokes equations with heat transfer. The intrusive polynomial chaos method incorporates uncertain variables as combinations of orthogonal polynomials, known as polynomial chaos expansions (PCEs), directly into the governing equations. This transformation turns the original deterministic PDEs into coupled deterministic equations for the PCE coefficients. We apply first-order IPCM and propose a decoupling approach for state and sensitivity systems. We discretize the state equations and their sensitivity using the Finite Element-Volume (FEV) method. We establish a stability estimate for the continuous and discrete state and sensibility equations.

本文采用入侵多项式混沌方法（IPCM）分析了含传热的Navier-Stokes方程传热问题的敏感性。入侵多项式混沌方法将不确定变量作为正交多项式的组合，即多项式混沌展开（pce），直接纳入控制方程。这种转换将原来的确定性偏微分方程转化为耦合的确定性偏微分方程系数。我们应用一阶IPCM，并提出一种状态和灵敏度系统的解耦方法。采用有限元体积法对状态方程及其灵敏度进行离散化。我们建立了连续和离散状态方程和灵敏度方程的稳定性估计。

引用次数: 0

An analytical model for whirlwinds of finite width rising with bounded velocity and decaying outflow: Application to dust devils 有限宽度有界上升速度和衰减出口漩涡的解析模型：在尘卷风中的应用

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-12-27 DOI: 10.1016/j.euromechflu.2025.204451

Sanjay Kumar Pandey, Kriti Yadav

This study presents an analytical model that extends previous formulations by incorporating axial dependence in all velocity components, thus offering a more realistic representation of dust devil dynamics. We address the limitations of the fundamental model of Vyas and Majdalani (2006), such as unbounded velocity and infinite vortex width, by modifying the stream function, which captures radial and axial variation of velocity. The velocity components are physically bounded and consistent with observed vortex structures. Additionally, the radial pressure distribution is derived, and the flow field is analysed using normalized radial, axial, and azimuthal velocities. The azimuthal velocity is computed from the radial and axial flows using the angular momentum equation. It increases from the centre, peaks near the periphery, and gradually decays to zero toward the axis. This model represents the compact features of dust devils by producing a smooth, confined structure with consistent vertical dependence, unlike alternative models that introduce abrupt transitions or unbounded behaviour. The profile maintains central stability in accordance with the Rayleigh criterion, while peripheral centrifugal instability reflects the transient and dissipative nature of dust devils. The model captures dust lifting and charge separation in dust devils, linking strong updrafts and confined flow to enhanced electrification and particle transport.

本研究提出了一个分析模型，通过在所有速度分量中纳入轴向依赖性，扩展了以前的公式，从而提供了一个更现实的尘暴动力学表示。我们通过修改流函数来解决Vyas和Majdalani（2006）的基本模型的局限性，例如无界速度和无限涡旋宽度，该流函数捕获了速度的径向和轴向变化。速度分量在物理上是有界的，与观测到的涡结构一致。此外，导出了径向压力分布，并使用归一化的径向、轴向和方位角速度分析了流场。用角动量方程从径向流和轴向流计算方位角速度。它从中心开始增加，在外围附近达到峰值，并逐渐向轴衰减到零。与引入突变或无界行为的其他模型不同，该模型通过产生具有一致垂直依赖性的光滑、受限结构来代表尘卷风的紧凑特征。剖面保持中心稳定符合瑞利准则，而外围离心不稳定反映了尘卷的瞬态和耗散性质。该模型捕获了尘卷中的粉尘提升和电荷分离，将强大的上升气流和受限流动与增强的电气化和粒子传输联系起来。

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引用次数: 0

Analysis of compliant tube properties and operating conditions in a Liebau pump 利宝泵柔性管特性及运行条件分析

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-12-26 DOI: 10.1016/j.euromechflu.2025.204450

Manuel Rubio , Francisco Castro-Ruiz , José Sierra-Pallares , César Barrios-Collado , Joaquín Anatol

This study examines asymmetric pumping in Liebau pumps, a type of valveless pump that generates unidirectional flow through the periodic compression of a flexible (compliant) tube. This pumping has applications in biomedical devices, microfluidics, and organ support. We investigate how the properties of the compliant tube and the operating conditions affect the pump performance, using dimensionless parameters. Experiments were performed with different configurations, varying the tube material (latex and rubber) and the fluid (water and water–glycerine mixture). The results indicate that the flow rate and resonant period depend on the stiffness of the tube and the viscous effects. It was observed that for small values of the Womersley number (

{W o}^{2}

), viscous effects significantly reduce the flow rate. In contrast, for large Womersley values, the semiempirical models previously proposed adequately predict the experimental behaviour. Effects such as the compliant tube depression, which were not accounted for in previous models, were also found to influence performance. This work extends the analysis of this type of pump to unexplored conditions, with the aim of expanding knowledge and enabling the use of Liebau pumps in real-world applications.

本研究考察了Liebau泵中的不对称泵送，Liebau泵是一种无阀泵，通过对柔性（柔性）管的周期性压缩产生单向流动。这种泵送在生物医学设备、微流体和器官支持方面有应用。我们使用无量纲参数研究了弯曲管的特性和操作条件对泵性能的影响。实验以不同的结构进行，不同的管材料（乳胶和橡胶）和流体（水和水-甘油混合物）。结果表明，流量和共振周期取决于管道的刚度和粘性效应。观察到，当沃默斯利数（Wo2）较小时，粘性效应显著降低了流速。相比之下，对于较大的沃默斯利值，先前提出的半经验模型可以充分预测实验行为。在以前的模型中没有考虑到的弯曲管凹陷等影响也会影响性能。这项工作将这种类型的泵的分析扩展到未开发的条件，目的是扩大知识和在实际应用中使用Liebau泵。

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引用次数: 0

Electron acoustic solitary wave in quantum plasmas with Kappa electrons 具有Kappa电子的量子等离子体中的电子声孤波

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-12-23 DOI: 10.1016/j.euromechflu.2025.204449

Aakanksha Singh, Punit Kumar

Electron-acoustic solitary waves (EASWs) in quantum plasma comprising stationary ions, cold electrons, hot electrons, and kappa-distributed electrons have been investigated. The generalized Kappa-Fermi distribution has been modified to include electrostatic energy contribution and the number density of Kappa electrons has been obtained using this modified distribution. Utilizing the quantum hydrodynamic (QHD) model, a dispersion relation has been derived for linear EAWs. Employing the standard reductive perturbation technique, a Korteweg–de Vries (KdV) equation governing the dynamics of EAWs have been derived. The quantum mechanical effects of different parameters like kappa index, Mach number and equilibrium kappa electron density have been examined on the profiles of EASWs. It is found that the presence of kappa electrons in quantum plasma leads to new results, including steeper dispersion curves, sharper and more localized solitary waves with lower value of kappa index and stronger plasma interactions with increased kappa electrons density in dense astrophysical environment.

研究了由固定离子、冷电子、热电子和kappa分布电子组成的量子等离子体中的电子声孤波。对广义Kappa- fermi分布进行了修正，使其包含静电能量的贡献，并由此得到了Kappa电子的数密度。利用量子流体力学（QHD）模型，推导了线性ews的色散关系。采用标准的约化微扰技术，推导了一个控制电畴动力学的KdV方程。考察了kappa指数、马赫数和平衡kappa电子密度等参数对EASWs谱线的量子力学效应。研究发现，在致密的天体物理环境中，量子等离子体中kappa电子的存在导致了新的结果，包括色散曲线更陡，kappa指数更低，孤立波更尖锐，更局域化，kappa电子密度增加，等离子体相互作用更强。

引用次数: 0