European Journal of Mechanics B-fluids最新文献

{"title":"Evaluating the effects of bronchioles simplification on respirable dust deposition: A combined experimental and CFD-DPM analysis approach","authors":"Ahmed Aboelezz ,&nbsp;Wei-Chung Su ,&nbsp;Mohammad Rezaee ,&nbsp;Pedram Roghanchi","doi":"10.1016/j.euromechflu.2025.204340","DOIUrl":"10.1016/j.euromechflu.2025.204340","url":null,"abstract":"<div><div>The resurgence of black lung disease among miners underscores the pressing need to enhance our understanding of respirable dust deposition mechanisms. This paper critically evaluates the widespread practice of simplifying bronchioles geometries in dust deposition studies, a method commonly employed but often without adequate consideration of its impact on particle–wall interactions and subsequent deposition calculations. Through the integration of experimental setups with computational simulations, this study investigates the behavior of respirable coal dust using Particle Image Velocimetry (PIV) and a specially designed dust wind tunnel equipped with both complex and simplified bronchioles models. Further, this research employs Computational Fluid Dynamics-Discrete Phase Model (CFD-DPM) simulations within ANSYS Fluent, incorporating these diverse models to assess the ramifications of geometrical simplification. A bronchioles wall observing model was introduced to enhance the simulation’s realism by more accurately representing the dynamic interactions between dust particles and bronchioles wall surfaces. The complex model showed about 1.5×higher dust deposition compared to the simplified model. This difference was partially attributed to its larger surface area, with a surface area ratio of approximately 1.92. A correction factor based on this ratio was proposed to enhance the predictive capability of simplified models. This approach not only sheds light on the significant influences of particle size and airway geometry on dust deposition but also challenges the reliability of simplified models in replicating these complex processes. This work contributes valuable insights into improving occupational health safety measures in mining and related industries, highlighting the need for careful consideration of model selection and its implications in environmental health research.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"114 ","pages":"Article 204340"},"PeriodicalIF":2.5,"publicationDate":"2025-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144852745","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":"Mean flow characteristics in horizontal and vertical channels with unstable stratification by buoyancy for liquid lead","authors":"Xingguang Zhou ,&nbsp;Dalin Zhang ,&nbsp;Xinyu Li ,&nbsp;Wentao Guo ,&nbsp;Hongxing Yu ,&nbsp;Wenxi Tian ,&nbsp;Suizheng Qiu ,&nbsp;Guanghui Su","doi":"10.1016/j.euromechflu.2025.204344","DOIUrl":"10.1016/j.euromechflu.2025.204344","url":null,"abstract":"<div><div>In this work, a further study on turbulence states and structures in horizontal and vertical channels for liquid lead with unstable stratification by buoyancy is carried out based on the latest published high-fidelity direct numerical simulation (DNS) database. The mixed flow in horizontal and vertical channel conditions at <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>τ</mi></mrow></msub><mo>=</mo><mn>150</mn></mrow></math></span>, <span><math><mrow><mi>P</mi><mi>r</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>025</mn></mrow></math></span>, and <span><math><mrow><mi>R</mi><mi>i</mi><mo>=</mo><mn>0</mn></mrow></math></span>, 0.25, 0.5, 1 are considered. The turbulence states of liquid lead with different buoyant effects are studied with Lumley triangle. The results indicate that different buoyant effects have a remarkable impact on turbulence states, in which the collapse of invariant trajectories in outer region suggests similarity. Large-scale organized motions and large-scale thermal structures are identified through instantaneous fields and quantitatively analyzed using one-dimensional premultiplied wavenumber spectra. The typical spanwise wavelengths of large-scale organized motions and large-scale thermal structures induced by buoyancy are approximately <span><math><mrow><mn>3</mn><mi>δ</mi></mrow></math></span> and <span><math><mrow><mn>2</mn><mi>π</mi><mi>δ</mi></mrow></math></span>, respectively, where <span><math><mi>δ</mi></math></span> is channel half-width. Detailed analyses with intuitive instantaneous fields and quantitative premultiplied wavenumber spectra are performed to investigate physical mechanisms in mixed channel flows with different buoyant effects for liquid lead. It is expected that this study would give insights into mean flow characteristics in mixed horizontal and vertical channel flows with unstable stratification for liquid lead.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"114 ","pages":"Article 204344"},"PeriodicalIF":2.5,"publicationDate":"2025-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144840715","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 study on impact dynamics of droplet on heated copper surfaces and liquid gallium surfaces","authors":"Lu Liu ,&nbsp;Zhihua Liu ,&nbsp;Fantai Meng ,&nbsp;Teng Wang ,&nbsp;Tai Wang ,&nbsp;Xinyu Dong","doi":"10.1016/j.euromechflu.2025.204346","DOIUrl":"10.1016/j.euromechflu.2025.204346","url":null,"abstract":"<div><div>The research on droplet impact has always focused on rigid solid surfaces. In the past two decades, the study of droplet impact dynamics on soft substrates, represented by PDMS, has received increasing attention, mainly driven by the development of flexible electronic technology. However, research on the dynamics of droplet impact on liquid metal surfaces is still relatively insufficient. Compared with PDMS, liquid metals exhibit higher surface tension and lower viscoelasticity, indicating that their droplet impact dynamic behavior will be significantly different. This paper reports the experiments for ethanol droplets impact heated copper surfaces and liquid gallium surfaces, and the effects of the Weber number (<em>We</em>) and surface temperature were analyzed. The results show that the patterns of droplet impact heated copper surfaces and liquid gallium surfaces can be divided into reflection rebound, central jetting, rebound rotation, jetting with horizontal splashing, and breakup. The impact dynamics of droplets on copper surfaces mainly depend on <em>We</em>, while the impact dynamics of droplets on liquid gallium surfaces are related to both <em>We</em> and surface temperature. As the surface temperature of liquid gallium increases, droplet rotation and splashing are suppressed, and the droplet maximum spreading diameter <em>D</em>_max decreases. A semi-empirical model for the maximum spreading diameter of droplets was established by introducing surface temperature correction to consider energy dissipation caused by surface deformation and viscoelasticity. The research results contribute to understanding the influences of surface deformation and viscoelasticity on droplet dynamics.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"114 ","pages":"Article 204346"},"PeriodicalIF":2.5,"publicationDate":"2025-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144852746","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":"Assessment of heat and mass transfer in a porous n-shaped heat exchanger using hybrid nanofluid under cross-diffusion and magnetic effects","authors":"Souhail Souai ,&nbsp;Mahadul Islam ,&nbsp;Samrat Hansda ,&nbsp;Soraya Trabelsi ,&nbsp;Sabrine Garrouri ,&nbsp;Mamun Molla ,&nbsp;Ezeddine Sediki","doi":"10.1016/j.euromechflu.2025.204337","DOIUrl":"10.1016/j.euromechflu.2025.204337","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Optimizing the geometry of cooling systems is vital for achieving the best thermal performance, ensuring energy efficiency, and supporting sustainability. This study introduces a novel approach by exploring the potential of a non-toxic hybrid nanofluid, an 80:20 water-propylene glycol blend combined with multi-walled carbon nanotubes (MWCNT) and iron oxide (Fe₃O₄) nanoparticles, within an innovative n-shaped heat exchanger. The research focuses on the impact of heat and mass sources on magnetohydrodynamic double-diffusive mixed convection (MHD-DDMC), emphasizing the intricate interactions between porous media, nanoparticle dynamics, cross-diffusion effects, and magnetic fields. Numerical simulations are conducted using the lattice Boltzmann method (LBM) to analyze the system's behavior. A sensitivity analysis, supported by Response Surface Methodology (RSM) and Analysis of Variance (ANOVA), quantifies the effects of various parameters on heat and mass transfer, establishing correlations for the average Nusselt number (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;Nu&lt;/mi&gt;&lt;/mrow&gt;&lt;mo&gt;̅&lt;/mo&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) and Sherwood number (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;Sh&lt;/mi&gt;&lt;/mrow&gt;&lt;mo&gt;̅&lt;/mo&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;). Various dimensionless variables, including porosity (ε), nanoparticles volume fraction (ϕ), source size (a), Lewis number (Le), Richardson number (Ri), buoyancy ratio (Br), Darcy number (Da), Hartmann number (Ha), Soret number (S&lt;sub&gt;r&lt;/sub&gt;), and Du&lt;sub&gt;&lt;em&gt;f&lt;/em&gt;&lt;/sub&gt;our number ( D&lt;sub&gt;&lt;em&gt;f&lt;/em&gt;&lt;/sub&gt;), were evaluated to understand their effect on fluid structure, heat, and mass transfer. The results show that as Le increases, &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;Nu&lt;/mi&gt;&lt;/mrow&gt;&lt;mo&gt;̅&lt;/mo&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; decreases by 23 % at a= 0.1, while the average &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;Sh&lt;/mi&gt;&lt;/mrow&gt;&lt;mo&gt;̅&lt;/mo&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; increases by 81 % at a= 0.3. Rising Ha from 0 to 90 causes &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;Nu&lt;/mi&gt;&lt;/mrow&gt;&lt;mo&gt;̅&lt;/mo&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; to decrease by 58 %, and &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;Sh&lt;/mi&gt;&lt;/mrow&gt;&lt;mo&gt;̅&lt;/mo&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; to decrease by 58 % at a= 0.3. Furthermore, reducing Da from 10⁻¹ to 10⁻⁵ results in the highest increase in &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;Nu&lt;/mi&gt;&lt;/mrow&gt;&lt;mo&gt;̅&lt;/mo&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; by 56 %, and the largest rise in &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;Sh&lt;/mi&gt;&lt;/mrow&gt;&lt;mo&gt;̅&lt;/mo&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; by 67 % at a= 0.3. Sensitivity analysis revealed that the ϕ, D&lt;sub&gt;&lt;em&gt;f&lt;/em&gt;&lt;/sub&gt;, and parameters Br, S&lt;sub&gt;&lt;em&gt;r&lt;/em&gt;&lt;/sub&gt;, and Ri are among the most influential parameters, with their effects on heat and mass transfer being statistically significant according to ANOVA results. At high concentrations, ϕ enhances heat transfer, while D&lt;sub&gt;&lt;em&gt;f&lt;/em&gt;&lt;/sub&gt; significantly improves mass transfer. Additionally, &lt;span&gt;&lt;math&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;, Br, S&lt;sub&gt;&lt;em&gt;r&lt;/em&gt;&lt;/sub&gt;, and ϕ positively contribute to b","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"114 ","pages":"Article 204337"},"PeriodicalIF":2.5,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144772120","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":"Control of stationary Görtler vortices-induced high-speed boundary layer transition: Localized steady uniform blowing","authors":"G.L. Huang,&nbsp;A. Wang,&nbsp;X. Chen,&nbsp;G.H. Tu,&nbsp;J.Q. Chen","doi":"10.1016/j.euromechflu.2025.204335","DOIUrl":"10.1016/j.euromechflu.2025.204335","url":null,"abstract":"<div><div>An investigation of effects of the localized steady uniform blowing (LSUB) on stationary Görtler vortices in a Mach 6.5 flow over a concave wall was carried out by solving two dimensional spatial eigenvalue problem (BiGlobal) and plane-marching parabolized stability equations (PSE3D) with help of direct numerical simulations (DNS). In the simulations, Görtler vortices are excited with spanwise wavelengths of 3 mm (1.5<span><math><mi>δ</mi></math></span>, <span><math><mi>δ</mi></math></span> is the thickness of boundary layer at <span><math><mi>x</mi></math></span> = 80 mm where the concave wall starts). No-slip and adiabatic conditions are prescribed at the wall. The flow visualization reveals prominent sinuous perturbations in the transition process. When the LSUB is applied to the wall, the boundary layer becomes thicker. With the increase in the amplitude of the LSUB within an appropriate range, Görtler streaks keep more regular and do not break down even at the end of the model when the amplitude of the LSUB is 0.01 of the free-stream velocity. Subsequent stability analyses based on BiGlobal and PSE3D confirm that sinuous secondary instability modes are the most unstable, responsible for the breakdown of Görtler vortices, and the growth rates of the dominant sinuous mode decrease significantly with increasing the amplitude of the LSUB. Further analysis indicates that the LSUB remarkably delays the growth of Görtler vortices, thus reducing the spanwise gradient of the streamwise velocity, which results in the decreases of energy production of the spanwise velocity shear. Therefore, the sinuous secondary instability is stabilized, leading to the delay of boundary layer transition. Our work suggests an appealing transition control strategy for high-speed flows dominated by Görtler vortices.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"114 ","pages":"Article 204335"},"PeriodicalIF":2.5,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144780838","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":"Investigation of the working mechanism and unsteady effects inside a single-outlet vortex tube by implementing unsteady computational fluid dynamics and spectral proper orthogonal decomposition","authors":"Sichang Xu,&nbsp;Gary W. Rankin","doi":"10.1016/j.euromechflu.2025.204341","DOIUrl":"10.1016/j.euromechflu.2025.204341","url":null,"abstract":"<div><div>Although various steady and unsteady working mechanisms underlying energy separation in Ranque–Hilsch vortex tubes have been investigated since the 1930s, a clear consensus has yet to be established. In the present research, unsteady energy separation mechanisms in a single-outlet vortex tube are investigated. The single vortex tube is modelled using both steady and unsteady Computational Fluid Dynamics (CFD) approaches. The unsteady CFD simulations are conducted using a Detached Eddy Simulation, and the steady simulations are performed with the Reynolds Stress Model. The experimental energy separation performance of a single-outlet vortex tube reported in the literature, with and without damping of the unsteady disturbances, is reproduced numerically. The explanation given in the original work, which describes energy separation as a result of changes in the time-averaged tangential velocity profile due to acoustic streaming, is not supported by the current numerical results. Therefore, a further investigation is made to determine other unsteady mechanisms occurring within the device. The inherent complexity of the transient three-dimensional flow field complicates the interpretation of fundamental flow structures and their associated unsteady dynamics. This is overcome by applying Spectral Proper Orthogonal Decomposition (SPOD) to the CFD dataset. Analysis of the dominant SPOD modes reveals two unsteady mechanisms within the flow field, including the radial transport and dissipation of vortical structures as well as the rotation of semi-coherent “blades” formed by Rossby vortices. An important finding of this study is that the combined effect of these mechanisms accounts for the energy separation observed in the single-outlet vortex tube.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"114 ","pages":"Article 204341"},"PeriodicalIF":2.5,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144781366","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":"Infinite series formulation for slip flow through a finite thickness orifice plate","authors":"Michael S.H. Boutilier,&nbsp;Rohit G.S. Ghode","doi":"10.1016/j.euromechflu.2025.204329","DOIUrl":"10.1016/j.euromechflu.2025.204329","url":null,"abstract":"<div><div>Liquid transport through membrane nanopores is often modelled as creeping flow through a finite thickness orifice plate. Experiments and molecular simulations have revealed the importance of slip in such pores, where the diameter can be orders of magnitude smaller than the slip length for materials such as carbon nanotubes and graphene. Approximate hydrodynamic resistance models considering access resistance to the pore and fully developed slip flow within the pore are sometimes applied to estimate flow rates. While this approach is very accurate without slip, it can result in large errors for long slip lengths. Even with large slip lengths, flow development in the entry/exit regions contribute significant pressure drops that should be accounted for. In this paper, we extend an infinite series formulation for no-slip creeping flow through a finite thickness orifice plate to slip flow through the same geometry. We develop an algebraic system of equations for the series coefficients that can be efficiently computed to determine the velocity and pressure fields for the selected pore aspect ratio and slip length. Accurate volume flow rates can be quickly calculated, and are tabulated for convenience. We refine the approximate hydrodynamic resistance model for this flow to include losses in the entry region and obtain a fit for the volume flow rate accurate to within 2.5% for all slip lengths and pore aspect ratios.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"114 ","pages":"Article 204329"},"PeriodicalIF":2.5,"publicationDate":"2025-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144852743","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":"Directional dependence of fluid flow on mixed convection across an isoflux cylinder with entropy generation","authors":"Rupam Saha ,&nbsp;B. Hema Sundar Raju","doi":"10.1016/j.euromechflu.2025.204330","DOIUrl":"10.1016/j.euromechflu.2025.204330","url":null,"abstract":"<div><div>This article explores the impact of free-stream flow orientation on the dynamics of flow past a circular cylinder under superimposed thermal buoyancy subjected to isoflux condition. It emphasizes how thermal buoyancy regulates boundary layer separation across different flow angles, offering valuable insights for optimizing thermal management in mixed convection systems. The effect caused by the fluid flow and thermal dynamics is highlighted along with entropy generation around the cylinder for various Reynolds numbers (<span><math><mrow><mn>5</mn><mo>≤</mo><mi>R</mi><mi>e</mi><mo>≤</mo><mn>40</mn></mrow></math></span>), Richardson numbers (<span><math><mrow><mn>0</mn><mo>≤</mo><mi>R</mi><mi>i</mi><mo>≤</mo><mn>1</mn><mo>.</mo><mn>5</mn></mrow></math></span>), and free-stream angles (<span><math><mrow><msup><mrow><mn>0</mn></mrow><mrow><mo>∘</mo></mrow></msup><mo>≤</mo><mi>α</mi><mo>≤</mo><mn>18</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>∘</mo></mrow></msup></mrow></math></span>). A fourth-order accurate finite difference scheme with a stable pseudo-time iterative method is developed to address the non-linear governing continuity, momentum and energy equations. The key findings reveal that the flow configuration remains symmetric along aiding and opposing flow regimes; otherwise, it becomes completely asymmetric. The superimposed thermal buoyancy controls the wake formation, which is strongly dependent upon the thermal boundary condition and flow orientation. Critical Richardson number (<span><math><mrow><mi>R</mi><msub><mrow><mi>i</mi></mrow><mrow><mi>c</mi><mi>r</mi></mrow></msub></mrow></math></span>) for suppressing the vortex shedding is evaluated for various parameters, and inter-parametric dependence of the <span><math><mrow><mi>R</mi><msub><mrow><mi>i</mi></mrow><mrow><mi>c</mi><mi>r</mi></mrow></msub></mrow></math></span> is also disclosed under isoflux boundary condition. The rate of heat transfer increases within aiding to cross flow regime, whereas the same decreases within cross to opposing flow regime. The relative contribution of heat transfer entropy to the overall entropy, characterized by Bejan number, reduces with increasing <span><math><mrow><mi>R</mi><mi>i</mi></mrow></math></span> in aiding and cross flow regime, while it increases in opposing flow regime.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"114 ","pages":"Article 204330"},"PeriodicalIF":2.5,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144713452","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":"New experiment for the pipe friction factor at high Reynolds numbers and comparisons for the degree of equivalence","authors":"Marie Ono ,&nbsp;Felix Heitmann ,&nbsp;Markus Juling ,&nbsp;Hannes Krüger ,&nbsp;Noriyuki Furuichi","doi":"10.1016/j.euromechflu.2025.204336","DOIUrl":"10.1016/j.euromechflu.2025.204336","url":null,"abstract":"<div><div>In this study, pipe friction factors ranging from <em>Re</em>_D ＝ 1.2 × 10⁴–4.0 × 10⁶ were determined at the Gravimetric Thermal Energy Standard (GraTESt) flow facility at the Physikalisch-Technische Bundesanstalt (PTB) in Berlin over a temperature range of 20 °C to 80 °C through measurement of the differential pressure. The bulk velocity was directly obtained from high-precision flow rate measurements, and the upstream length of the test section was 156 <em>D</em>. The results measured at different temperatures show good agreement with each other at the same Reynolds numbers, within the estimated uncertainty. The difference between the present results and previous studies at the Hi-Reff flow facility at the National Metrology Institute of Japan (NMIJ) (Furuichi et al., 2015, <em>Phys. Fluid</em>), is within ± 0.3 % over a wide range of Reynolds numbers from <em>Re</em>_D ＝ 3.3 × 10⁴–1.1 × 10⁶, confirming the consistency between GraTESt and Hi-Reff. At larger Reynolds numbers, the difference between GraTESt and Superpipe (McKeon et al., 2004, <em>J. Fluid Mech.</em>) increases, reaching ± 1.0 % at <em>Re</em>_D ＝ 4.0 × 10⁶. To objectively assess the degree of equivalence of friction factor results in present and previous studies, six data sets are quantitatively compared using an objective indicator, the Key Comparison Reference Value (KCRV). Based on the KCRV, a consensus between friction factors is achieved at <em>Re</em>_D ≈ 3 × 10⁴–3 × 10⁵. However, the degree of equivalence was low at other Reynolds numbers. Further experiments are required to accurately determine the friction factor and its scaling, especially at high Reynolds numbers.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"114 ","pages":"Article 204336"},"PeriodicalIF":2.5,"publicationDate":"2025-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144748943","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":"Bénard–von Kármán vortex street in a spin–orbit-coupled Bose–Einstein condensate with nonlocal Rydberg interactions","authors":"Zhong-Hong Xi ,&nbsp;Yu-Ren Shi","doi":"10.1016/j.euromechflu.2025.204332","DOIUrl":"10.1016/j.euromechflu.2025.204332","url":null,"abstract":"<div><div>The dynamics of a Rashba-type spin–orbit-coupled Bose–Einstein Condensate with nonlocal Rydberg interactions stirred by a moving cylindrical obstacle potential are investigated numerically. The results show that the Bénard–von Kármán vortex street consisting of quantized vortex pairs emerge in both component of Rydberg-dressed Bose–Einstein Condensate for appropriate velocity and width of the moving potential. By tracking two point vortices in a pair of the vortex street, we find that the angular velocity at which two point vortices rotates around their center is inversely proportional to the square of distance between two point vortices. The other typical vortex shedding patterns such as stable laminar flow, vortex dipoles, drifting vortex dipoles, V-shaped vortex pairs and irregular turbulence can also be observed. The parameter regions under different Rydberg interactions for various vortex patterns is obtained by systematic numerical simulations. The influence of the Rydberg interaction strength on the vortex street is studied. The drag force exerted by the wake on the moving potential correspond to different vortex shedding patterns is calculated and analyzed. Finally, an experimental protocol to realize the vortex street in Rydberg-dressed Bose–Einstein Condensate is provided.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"114 ","pages":"Article 204332"},"PeriodicalIF":2.5,"publicationDate":"2025-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144711320","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}