European Journal of Mechanics B-fluids最新文献

{"title":"Study on the energy dissipation mechanism of three-degree-of-freedom acoustic vibration system due to high-viscosity fluid motion","authors":"Lei Yu,&nbsp;Xiaobin Zhan,&nbsp;Tielin Shi","doi":"10.1016/j.euromechflu.2026.204473","DOIUrl":"10.1016/j.euromechflu.2026.204473","url":null,"abstract":"<div><div>This paper is aimed to study the energy dissipation mechanism of the three-degree-of-freedom (three-DOF) acoustic vibration system due to high-viscosity fluid motion. A simulation model describing the dynamic interaction between a three-DOF acoustic vibration system and the fluid is established using computational fluid dynamics (CFD) and fluid-structure interaction (FSI) methods. The simulation results show that under acoustic vibration excitation, the fluid inside the vessel rapidly transitions from a relatively stationary state to violent motion behavior. The key factor in the energy dissipation of the fluid is caused by the phase difference between the fluid force as the fluid impacts on the wall and the motion imposed on the vessel. The energy input to the system is primarily dissipated by the fluid and the structural damping of the system. The effects of excitation amplitude, excitation frequency, filling ratio, and fluid viscosity on the energy dissipation of the system are also analyzed in this study. An increase in the excitation amplitude as well as an increase in the excitation frequency within a certain frequency range, results in an enhancement of the systems' dynamic response, which leads to a significant increase in the energy input to the system and the energy dissipated by the fluid. In the range of filling ratios investigated in this study, the total input energy and fluid dissipation energy are minimized at the filling ratio of 50 %. Furthermore, an increase in fluid viscosity results in higher fluid energy dissipation and input energy.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"118 ","pages":"Article 204473"},"PeriodicalIF":2.5,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146035438","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 convective instability analysis of a channel flow within a saturated porous medium","authors":"V. Kandavelu ,&nbsp;L. Tlau ,&nbsp;P.T. Griffiths","doi":"10.1016/j.euromechflu.2026.204474","DOIUrl":"10.1016/j.euromechflu.2026.204474","url":null,"abstract":"<div><div>The influence of convection in a horizontal channel filled with a porous medium is examined to assess the stability of the fluid flow between the two walls that are held fixed at different temperatures. The flow is described by the Navier–Stokes equations, while heat transfer is captured through the energy equation. A coupled linear stability system is derived and solved using a Chebyshev spectral collocation method. The study focuses on the impact of the relevant nondimensional parameters on the development of the perturbations and the onset of instability within the flow. The onset of convection is advanced as the porous parameter <span><math><mrow><mo>(</mo><mi>M</mi><mo>)</mo></mrow></math></span> increases, while higher Prandtl numbers <span><math><mrow><mo>(</mo><mi>P</mi><mi>r</mi><mo>)</mo></mrow></math></span> and Reynolds numbers <span><math><mrow><mo>(</mo><mi>R</mi><mi>e</mi><mo>)</mo></mrow></math></span> delay the onset of convection. The growth rate is unaffected by increases in <span><math><mrow><mi>P</mi><mi>r</mi></mrow></math></span> and the Rayleigh number <span><math><mrow><mo>(</mo><mi>R</mi><mi>a</mi><mo>)</mo></mrow></math></span>; however, it increases as <span><math><mi>M</mi></math></span> decreases and as <span><math><mrow><mi>R</mi><mi>e</mi></mrow></math></span> increases. The isocontours show that increasing <span><math><mrow><mi>P</mi><mi>r</mi></mrow></math></span> stabilizes temperature variations in the inner flow region.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"118 ","pages":"Article 204474"},"PeriodicalIF":2.5,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146035439","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":"Parallel Social Group Optimization for physics-informed calibration of RANS turbulence models: Accuracy, robustness, and generalization","authors":"Amar Singh ,&nbsp;Vinod Kumar Shukla ,&nbsp;Sukanta Ghosh","doi":"10.1016/j.euromechflu.2026.204486","DOIUrl":"10.1016/j.euromechflu.2026.204486","url":null,"abstract":"<div><div>We present Parallel Social Group Optimization (PSGO) for physics-informed calibration of eddy-viscosity RANS closures, with a practical focus on separated, wall-bounded flows where, prediction hinges on accurate separation and reattachment. The method is derivative-free and HPC-friendly: multiple social groups evaluate independent RANS jobs in parallel while four staged operators (self-learning, improving, acquiring, combining) balance exploration and contraction. We first benchmark PSGO on continuous black-box test functions to validate optimizer reliability, then apply it to tune the coefficients of the SST k–ω model using a multi-case objective built from periodic hill and canonical wall-bounded flows. Under matched budgets, PSGO shows faster median convergence and lower run-to-run variability than GA/PSO/DE/CS (coefficient of variation 0.17 vs GA 0.41, PSO 0.36). Using the calibrated coefficients without re-tuning, we assess in-family transfer on an unseen backward-facing step at a single Reynolds number: the reattachment length improves from 7.2 h (baseline) to 6.3 h, close to DNS (6.0 h), and mean-velocity/pressure profiles are consistently closer to reference. The scope of this study is application-specific, eddy-viscosity RANS calibration for separation–reattachment flows at moderate Reynolds numbers; cross-physics and multi-Re robustness are outlined as future work.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"118 ","pages":"Article 204486"},"PeriodicalIF":2.5,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146185039","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":"Visualising coherent vortices generated by a swimming dolphin","authors":"Yutaro Motoori,&nbsp;Hideki Murahata,&nbsp;Susumu Goto","doi":"10.1016/j.euromechflu.2025.204452","DOIUrl":"10.1016/j.euromechflu.2025.204452","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"118 ","pages":"Article 204452"},"PeriodicalIF":2.5,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974618","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":"Yarn dynamics in a pneumatic guiding tube: Numerical simulation and experimental validation","authors":"Tianbo Liu,&nbsp;Qitao Huang,&nbsp;Yuliang Yan,&nbsp;Tianyi Wang,&nbsp;Jiahui Wang,&nbsp;Hongguang Xu","doi":"10.1016/j.euromechflu.2026.204464","DOIUrl":"10.1016/j.euromechflu.2026.204464","url":null,"abstract":"<div><div>The yarn in the pneumatic guiding tube has high fineness and considerable flexibility. As a result, it undergoes complex deformations under the airflow, making the fluid–structure interaction (FSI) between the yarn and airflow difficult to simulate. This study develops a weakly coupled numerical simulation framework to address this issue. The airflow and the fine yarn are modeled separately. The flow velocity is obtained using an upstream sampling method and applied to the yarn model. The yarn dynamics model is advanced using the implicit method. After updating the yarn position, the flow field is updated via force projection, thereby realizing a two-way FSI simulation. The kinematic and dynamic characteristics of yarn under pneumatic guiding tube control are systematically investigated through the framework. In yarn conveying process, the yarn quality flow stability and distribution concentration are found to increase first and then decrease with the increase of the input flow velocity. For the yarn tensioning process, the tension and vibration of the yarn continuously increase as the input velocity rises. The simulation framework is validated through experimental comparisons. Based on the simulation results and experimental data, the allowable ranges and optimal intervals of input velocity under different operating conditions are determined.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"118 ","pages":"Article 204464"},"PeriodicalIF":2.5,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074605","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 slip-yield stress model on the oscillatory squeeze flow of a viscoelastic fluid confined between two spheres","authors":"D. Matuz ,&nbsp;F. Méndez ,&nbsp;J. Arcos ,&nbsp;O. Bautista ,&nbsp;R. Baños","doi":"10.1016/j.euromechflu.2026.204466","DOIUrl":"10.1016/j.euromechflu.2026.204466","url":null,"abstract":"<div><div>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 <span><math><mi>r</mi></math></span>. 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 <span><math><mtext>De</mtext></math></span>, the Womersley number <span><math><mi>α</mi></math></span>, the Navier slip length <span><math><mover><mrow><mi>λ</mi></mrow><mrow><mo>̃</mo></mrow></mover></math></span>, the slip relaxation number <span><math><msub><mrow><mtext>De</mtext></mrow><mrow><mi>s</mi></mrow></msub></math></span> and the critical shear stress at the fluid–solid interface <span><math><msub><mrow><mover><mrow><mi>τ</mi></mrow><mrow><mo>̃</mo></mrow></mover></mrow><mrow><mi>c</mi></mrow></msub></math></span>. 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.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"118 ","pages":"Article 204466"},"PeriodicalIF":2.5,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974617","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 front airfoil leading-edge serrations on turbulence interaction noise characteristics of tandem airfoils at different angles of attack","authors":"Xishuai Yu,&nbsp;Jianxi Zhou,&nbsp;Yong Li","doi":"10.1016/j.euromechflu.2026.204463","DOIUrl":"10.1016/j.euromechflu.2026.204463","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"118 ","pages":"Article 204463"},"PeriodicalIF":2.5,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974619","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":"On the local anisotropy of quasi-two-dimensional forced shallow flow: An experimental study","authors":"G. Antar ,&nbsp;J. El Kuweiss ,&nbsp;K. Schneider ,&nbsp;C. Habchi ,&nbsp;S. Benkadda","doi":"10.1016/j.euromechflu.2025.204453","DOIUrl":"10.1016/j.euromechflu.2025.204453","url":null,"abstract":"<div><div>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 <em>via</em> the inverse energy cascade, with nonlinear interactions eventually influencing the perpendicular direction.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"118 ","pages":"Article 204453"},"PeriodicalIF":2.5,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145904126","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":"Nonlinear dynamics of dust-acoustic waves in cometary plasmas: Supernonlinear periodic waves, charge asymmetry, and thermal gradients bridging astrophysical and industrial applications","authors":"M.A. El-Borie ,&nbsp;Reem Altuijri ,&nbsp;Abdel-Haleem Abdel-Aty ,&nbsp;A. Atteya ,&nbsp;Pralay Kumar Karmakar ,&nbsp;Kottakkaran Sooppy Nisar ,&nbsp;Nadia Alsaeed Saad","doi":"10.1016/j.euromechflu.2026.204469","DOIUrl":"10.1016/j.euromechflu.2026.204469","url":null,"abstract":"<div><div>This work investigates the behavior of dust-acoustic waves (DAWs) in cometary plasmas including opposite-polarity dust grains, Maxwellian ions, and suprathermal electrons. We derived the modified Korteweg–de Vries (mKdV) equation to define periodic, superperiodic, and solitary wave solutions. Bifurcation analysis uncovers supernonlinear periodic waves (SPOs), a novel class of coherent structures sustained under extreme nonlinearity through precise nonlinear-dispersive balance. The phase velocity of DAWs is shown to rise with increasing positive-to-negative dust charge ratio, <span><math><msub><mrow><mi>α</mi></mrow><mrow><mi>d</mi></mrow></msub></math></span>, and negative-to-positive dust temperature ratio, <span><math><msub><mrow><mi>δ</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span>, while nonlinear coefficients decline, contrasting the dispersive term’s enhancement. Sagdeev potential analysis reveals dual energy minima governing compressive/rarefactive solitary waves, with thermal gradients <span><math><msub><mrow><mi>δ</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> modulating amplitude and width. Numerical simulations, benchmarked against laboratory parameters, demonstrate that heightened thermal contrast amplifies nonlinear coupling, driving larger-amplitude periodic waves. SPOs, distinguished by concentrated energy and potential turbulence onset, highlight efficient energy transport mechanisms critical to astrophysical plasmas. These findings advance predictive models for wave behavior in cometary tails, planetary rings, and laboratory experiments, offering insights into energy transfer, instability thresholds, and applications in space physics and industrial plasmas. The study bridges theoretical and observational gaps, underscoring the role of dust charge asymmetry and thermal gradients in shaping nonlinear wave dynamics.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"118 ","pages":"Article 204469"},"PeriodicalIF":2.5,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146035436","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 kinetic scheme based on positivity preservation for multi-component Euler equations","authors":"Shashi Shekhar Roy,&nbsp;S.V. Raghurama Rao","doi":"10.1016/j.euromechflu.2026.204490","DOIUrl":"10.1016/j.euromechflu.2026.204490","url":null,"abstract":"<div><div>A kinetic model with flexible velocities is presented for solving the multi-component Euler equations. The model employs a two-velocity formulation in 1D and a three-velocity formulation in 2D. In 2D, the velocities are aligned with the cell-interface to ensure a locally one-dimensional macroscopic normal flux in a finite volume. The velocity magnitudes are defined to satisfy conditions for preservation of positivity of density of each component as well as of overall pressure for first order accuracy under a CFL-like time-step restriction. Additionally, at a stationary contact discontinuity, the velocity definition is modified to achieve exact capture. The basic scheme is extended to third order accuracy using a Chakravarthy-Osher type flux-limited approach along with three-stage, third-order Strong Stability Preserving Runge–Kutta (SSPRK) method. Benchmark 1D and 2D test cases, including shock-bubble interaction problems, are solved to demonstrate the efficacy of the solver in accurately capturing the relevant flow features.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"118 ","pages":"Article 204490"},"PeriodicalIF":2.5,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146184962","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}