European Journal of Mechanics B-fluids最新文献

{"title":"Turbulent entrainment in buoyant releases from horizontal gravity current to vertical planar wall plume","authors":"Safir Haddad , Samuel Vaux , Kevin Varrall , Olivier Vauquelin","doi":"10.1016/j.euromechflu.2025.02.006","DOIUrl":"10.1016/j.euromechflu.2025.02.006","url":null,"abstract":"<div><div>This paper examines the dynamics of a supercritical, steady, miscible, two-dimensional gravity current flowing along an inclined boundary, with a particular focus on the entrainment, which refers to the mixing between the gravity current and the surrounding fluid. Specifically, the study investigates the combined effects of the Richardson number <span><math><mtext>Ri</mtext></math></span> and slope <span><math><mi>θ</mi></math></span> on the entrainment coefficient <span><math><mi>E</mi></math></span>. To address these objectives, a theoretical study and large-eddy simulations (LES) were conducted, varying the slope angle from 0° to 90°, while maintaining constant injection conditions.</div><div>The theoretical investigation of gravity currents resulted in the extension of the theoretical model of Ellison and Turner (1959) in the general non-Boussinesq case as well as the identification of two specific angles: the critical angle <span><math><msub><mrow><mi>θ</mi></mrow><mrow><mi>c</mi></mrow></msub></math></span>, beyond which no transition between supercritical to subcritical behaviour is observed, and the supercritical angle <span><math><msub><mrow><mi>θ</mi></mrow><mrow><mi>s</mi><mi>c</mi></mrow></msub></math></span>, above which the flow acquires inertia immediately after injection.</div><div>On the other hand, the simulations revealed three distinct flow regimes for our source conditions. The first regime, observed at low slopes, exhibits a non-monotonic behaviour, characterized by a transition from a supercritical to a subcritical regime. The second regime, related to the critical angle <span><math><msub><mrow><mi>θ</mi></mrow><mrow><mi>c</mi></mrow></msub></math></span>, occurs at intermediate slopes, where the flow remains inertial throughout. In the third regime, related to steeper slopes, the supercritical angle <span><math><msub><mrow><mi>θ</mi></mrow><mrow><mi>s</mi><mi>c</mi></mrow></msub></math></span> has been exceeded and the flow immediately gains inertia upon injection. The simulations also enabled an analysis of <span><math><mi>E</mi></math></span>, which was found to increase with slope and reach a constant value at <span><math><mrow><mi>θ</mi><mo>=</mo><mn>9</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>∘</mo></mrow></msup></mrow></math></span>.</div><div>Moreover, a new entrainment law was developed, incorporating both the effects of the Richardson number and the slope: <span><math><mrow><mi>E</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>002</mn><mo>cos</mo><mrow><mo>(</mo><mi>θ</mi><mo>)</mo></mrow><mo>/</mo><mtext>Ri</mtext><mo>+</mo><mn>0</mn><mo>.</mo><mn>09</mn><msup><mrow><mo>sin</mo></mrow><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msup><mrow><mo>(</mo><mi>θ</mi><mo>)</mo></mrow></mrow></math></span>. This law provides a description of the entrainment behaviour across the full range of slope angles. Comparisons between the LES results and the theoretical model demonstrate that the proposed entrainment law offers im","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"112 ","pages":"Pages 37-46"},"PeriodicalIF":2.5,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143521250","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":"Material barriers to the diffusive magnetic flux in magnetohydrodynamics","authors":"A. Encinas-Bartos ,&nbsp;B. Kaszás ,&nbsp;S. Servidio ,&nbsp;G. Haller","doi":"10.1016/j.euromechflu.2025.02.001","DOIUrl":"10.1016/j.euromechflu.2025.02.001","url":null,"abstract":"<div><div>Recent work has identified objective (frame-indifferent) material barriers that inhibit the transport of dynamically active vectorial quantities (such as linear momentum, angular momentum and vorticity) in Navier–Stokes flows. In magnetohydrodynamics (MHD), a similar setting arises: the magnetic field vector impacts the evolution of the velocity field through the Lorentz force and hence is a dynamically active vector field. Here, we extend the theory of active material barriers from Navier–Stokes flows to MHD flows in order to locate frame-indifferent barriers that minimize the diffusive magnetic flux in turbulent two-dimensional and three-dimensional MHD flows. From this approach we obtain an algorithm for the automated extraction of such barriers from MHD turbulence data. Our findings suggest that the identified barriers inhibit magnetic diffusion, separate electric current sheets and organize the transport of the magnetic energy.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"112 ","pages":"Pages 10-21"},"PeriodicalIF":2.5,"publicationDate":"2025-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143488698","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":"Unsteady Couette flow of a class of fluids described by non-monotone models","authors":"Lorenzo Fusi,&nbsp;Antonio Giovinetto,&nbsp;Rebecca Tozzi","doi":"10.1016/j.euromechflu.2025.02.005","DOIUrl":"10.1016/j.euromechflu.2025.02.005","url":null,"abstract":"<div><div>In this paper we study the unsteady Couette motion of an incompressible non-linear fluid driven by a prescribed shear stress or a prescribed velocity imposed on the top surface. The fluid under consideration is described by a non-monotone relation between stress and strain rate. We consider the two-dimensional unsteady problem and solve it numerically by means of Crank–Nicolson scheme combined with spectral collocation method. We investigate the time behaviour of the velocity field, in order to find out, starting from suitable initial conditions, whether the numerical solutions tend to the corresponding stationary one or not. Our results confirm both the stability of the two solutions belonging to the ascending branches of the constitutive law and the linear instability of the one on the descending branch.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"112 ","pages":"Pages 1-9"},"PeriodicalIF":2.5,"publicationDate":"2025-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143488697","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":"Numerical study of converging shock wave interaction with offset gas bubble containing different gases - Ne, Ar or CO2","authors":"D. Igra ,&nbsp;O. Igra","doi":"10.1016/j.euromechflu.2025.02.002","DOIUrl":"10.1016/j.euromechflu.2025.02.002","url":null,"abstract":"<div><div>This study presents a numerical investigation of the interaction between a converging shock wave and an offset cylindrical gas bubble containing Ne, Ar, or CO₂. Based on the good agreement with experimental findings shown in our previous study, we explored how these gases influence shock wave patterns when a converging shock wave propagating at a Mach number of 1.18 impacts a 50 mm diameter cylindrical bubble. The results reveal complex shock wave dynamics that differ from those observed when planar shocks impact on a cylindrical gas bubble or when a converging shock wave impacts a cylindrical gas bubble located at the center of its focus. Notably, in the case of a Ne-filled bubble, the shock wave focus is outside of the initial bubble location. Each gas produced distinct shock wave behaviors: the Ne bubble exhibited lens-like shock patterns, while in the Ar bubble's case the transmitted and converging shock waves were circular. A second shock wave focusing of the transmitted shock wave was observed inside the Ar bubble, similar to the case of the CO₂ bubble, which experienced earlier focusing than in the SF₆ case (previously studied) but later than Ar. The position of the transmitted shock wave's focus within the bubble varies with gas density, showing that heavier gases result in a focal point located further inside the bubble.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"112 ","pages":"Pages 22-36"},"PeriodicalIF":2.5,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143512495","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":"Flow structures in the near wake of permeable circular cylinders in shallow water","authors":"Ibrahim Mert Hakligor,&nbsp;Gokturk M. Ozkan,&nbsp;Huseyin Akilli","doi":"10.1016/j.euromechflu.2025.01.013","DOIUrl":"10.1016/j.euromechflu.2025.01.013","url":null,"abstract":"<div><div>The flow structure in the wake of circular screen cylinders was investigated experimentally by dye visualization and high-image density Particle Image Velocimetry (PIV) technique in shallow water. The effect of permeability was analyzed for four permeability ratios across varying Reynolds numbers. Results showed that permeability significantly influences the wake flow dynamics. Jet-like flow structures and Kelvin-Helmholtz instabilities with pulsating behavior were observed at minimum permeability, i.e., <em>β</em> = 0.4. As permeability increases, these structures extend downstream (<em>β</em> = 0.5), weaken (<em>β</em> = 0.6), or completely disappear for <em>β</em> = 0.7. Velocity deficits were found to be highest at <em>β</em> = 0.4 and decreased with greater permeability values. Turbulent fluctuations are dominant along shear layers that diminish with increasing permeability. Two-point spatial correlations revealed strong vortical interactions for <em>β</em> ≤ 0.5 that diminish for <em>β</em> ≥ 0.6. These findings highlight the critical role of permeability in the wake characteristics of circular screen cylinders, providing insights for relevant engineering applications.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"111 ","pages":"Pages 295-307"},"PeriodicalIF":2.5,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143396088","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":"Experimental investigation of synthetic jet impingement upon a honeycomb","authors":"Kangfu Sun ,&nbsp;Siying Zhang ,&nbsp;Nuo Shi ,&nbsp;Shaoqing Peng ,&nbsp;Jingguo Cao ,&nbsp;Jiao Sun ,&nbsp;Wenyi Chen","doi":"10.1016/j.euromechflu.2025.02.003","DOIUrl":"10.1016/j.euromechflu.2025.02.003","url":null,"abstract":"<div><div>We present an experimental study of synthetic jet vortex rings flowing through a honeycomb. A free synthetic jet generated by piston-cylinder apparatus is used to make a vortex, obtaining turbulence at Taylor Reynolds number <em>Re</em>_<em>λ</em> ∼ 294. We sketch a conceptual picture of the passive control of the flow field by honeycomb. By choosing a length-to-cell ratio <em>Φ</em> = 2.1, we clearly show how the honeycomb affects the evolution of vortical structure flowing through a honeycomb. The mechanism associated with vorticity cancellation is that the finger-type jets shaping downstream of the honeycomb will reorganize into a transmitted vortex ring in the downstream flow. We chose three length-to-cell ratios (<em>Φ</em> = 3.7, 6.3, and 12.5) with a constant length of honeycomb to examine the effect of their geometry on the flow characteristic. We find that honeycomb redistributes the flow field and enhances the uniformity of the flow field. In addition, the selection of the length-to-cell ratio of honeycomb should correspond to the given experimental conditions, because the turbulence reduction and isotropy are not mutually beneficial. The results of velocity triple-decomposition show that the honeycomb can effectively reduce the periodic and random velocity fluctuation, revealing the mechanism of a relaminarization.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"111 ","pages":"Pages 319-333"},"PeriodicalIF":2.5,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143403368","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":"Sensitivity analysis for incompressible Navier–Stokes equations with uncertain viscosity using polynomial chaos method","authors":"N. Nouaime ,&nbsp;B. Després ,&nbsp;M.A. Puscas ,&nbsp;C. Fiorini","doi":"10.1016/j.euromechflu.2025.01.012","DOIUrl":"10.1016/j.euromechflu.2025.01.012","url":null,"abstract":"<div><div>We present a stability estimate for the sensitivity of the incompressible Navier–Stokes equations under uncertainty in model parameters such as viscosity and initial or boundary conditions. The approach employs the stochastic Galerkin method, wherein the solution is represented using a generalized polynomial chaos expansion. The governing equations are projected onto stochastic basis functions, resulting in an extended coupled equation system. These coupled equations are challenging to solve numerically. A decoupling method is proposed to simplify their numerical resolution, which, along with the stability estimates, represents one of this study’s most valuable and original aspects. Finally, we present the lid-driven cavity numerical test to evaluate the polynomial chaos method and compare the solutions with the numerical data published in the literature.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"111 ","pages":"Pages 308-318"},"PeriodicalIF":2.5,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143396089","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":"Analytical solution for solitary wave diffraction around a cylinder surrounded by multi-segmented arc-shaped wall","authors":"Zhiqun Guo ,&nbsp;Jianming Miao ,&nbsp;Sen Liu ,&nbsp;Zhenfeng Zhai","doi":"10.1016/j.euromechflu.2025.01.010","DOIUrl":"10.1016/j.euromechflu.2025.01.010","url":null,"abstract":"<div><div>By modeling the unique segmented arc-shaped breakwater at the periphery of the shallow waters of Dubai’s Palm Island, this paper provides insights into the complex mechanisms of interaction between solitary waves and one cylinder surrounded by multi-segmented concentric arc-shaped outer wall. This study presents an analytical solution using the matched eigenfunction method. Matching conditions are used to determine the initially unknown potential coefficients, ensuring that boundary flux and velocity constraints are met. The numerical results show a high degree of agreement with previous studies. The study examines key factors influencing hydrodynamic loads and diffracted wave surfaces, including incident angle, radius ratio and segment spacing. The findings suggest that segmented triple arc facades with appropriate segmental spacing provide superior shielding effect compared to non-segmented arc facades and circular structures. Additionally, when the arc facade is permeable to water, segmentation has little impact on its shielding effect. The numerical findings offer valuable insights for the engineering design of segmented arc structures.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"111 ","pages":"Pages 283-294"},"PeriodicalIF":2.5,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143372938","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":"Simulation analysis of flow field optimization for powder bed surface integrity and spatter particle removal","authors":"Qingpeng Chen ,&nbsp;Tan Cheng ,&nbsp;Jiachen Yu ,&nbsp;Feixiang Tang ,&nbsp;Wei Wang ,&nbsp;Guoqing Zhang ,&nbsp;Fang Dong ,&nbsp;Sheng Liu","doi":"10.1016/j.euromechflu.2025.01.011","DOIUrl":"10.1016/j.euromechflu.2025.01.011","url":null,"abstract":"<div><div>Spatter particles are a major cause of part defects during laser powder bed fusion (LPBF). Filling the working chamber with an inert gas prevents oxidation of the part and simultaneously removes spatter particles. The flow of inert gas in the working chamber influences the spatter-particle trajectory. This study develops a new wind-duct circulation system design based on inert-gas flow characteristics. The inert gas flow characteristics in the chamber were investigated using a coupled computational fluid dynamics and discrete phase model. The Coanda effect influence on the wind field uniformity and motion trajectories of spatter particles in different regions of the LPBF chamber was analyzed. A Bernoulli-effect three-wind duct structure was designed to attenuate the Coanda effect, and the effects of nine sets of wind speed combinations were investigated. The results demonstrate that the newly designed three-wind duct structure effectively reduces the Coanda effect of the flow field inside the working chamber. Wind speed requirements in each functional area are ensured and the removal efficiency of spatter particles is enhanced (79–96 %). This solution addresses a critical issue found in existing commercial LPBF equipment, providing a reliable reference for the subsequent optimization and design of duct circulation systems.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"111 ","pages":"Pages 266-282"},"PeriodicalIF":2.5,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143093476","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":"Updating our perspective on the bi-directional equations of dissipative, finite-amplitude acoustics theory: From Blackstock (1963) to Diaz–Solovchuk–Sheu (2018)","authors":"P.M. Jordan","doi":"10.1016/j.euromechflu.2025.01.005","DOIUrl":"10.1016/j.euromechflu.2025.01.005","url":null,"abstract":"<div><div>The propagation of finite-amplitude acoustic wave-forms in thermoviscous gases, assumed to admit constant transport coefficients, under two newly-introduced third order, bi-directional, equations of motion is investigated. Along with analyzing both under the traveling wave assumption, the present study also compares the wave-profiles exhibited by these new models, the simplest of which follows from Diaz et al. (2018), with those of their established counterparts. Connections between equations that comprise this now expanded collection of six acoustic models are highlighted, and the degree of approximation required to derive each from the acoustic Navier–Stokes–Fourier system is indicated via a hierarchical chart. It is also shown that the long-established model with the fewest approximations and the newer, more heavily approximated, Diaz, et al. model yield the <em>same</em> Taylor shock traveling wave profile.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"111 ","pages":"Pages 244-249"},"PeriodicalIF":2.5,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143093477","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}