European Journal of Mechanics B-fluids最新文献

{"title":"A two-experiment approach to hydraulic jump scaling","authors":"Keith Davey ,&nbsp;Abdullah Al-Tarmoom ,&nbsp;Hamed Sadeghi","doi":"10.1016/j.euromechflu.2025.01.008","DOIUrl":"10.1016/j.euromechflu.2025.01.008","url":null,"abstract":"<div><div>A hydraulic jump is a sudden rapid transition from a fast to a slower moving flow that is readily observed in open channels. The phenomenon has been extensively investigated both theoretically and experimentally, and is influenced by turbulence, gravity, wall friction, and fluid viscosity. The behaviour of a jump changes under scaling, which limits experimental investigations performed at scale, making scaled models unrepresentative. This issue is addressed in this paper with the introduction of a new experimental approach involving more than one scaled model. A new theory for scaling has recently appeared in the open literature that systematically removes scale effects by means of alternative similitude rules not available to dimensional analysis. This main focus in this paper is on the rule known as the <em>first-order finite-similitude</em> rule, involving two scaled experiments. The question addressed in the paper is whether it is possible, by means of additional scaled experiments, to capture more accurately hydraulic-jump behaviour. Both theoretical and experimentally-validated results are examined from the literature to support the contention that an additional scaled experiment provides significantly improved outcomes.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"111 ","pages":"Pages 215-228"},"PeriodicalIF":2.5,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143093479","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":"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}

{"title":"Effect of imposed shear stress on the stability of surfactant-laden liquid film flow over a rod","authors":"Neha Jain,&nbsp;Gaurav Sharma","doi":"10.1016/j.euromechflu.2025.01.009","DOIUrl":"10.1016/j.euromechflu.2025.01.009","url":null,"abstract":"<div><div>The linear stability of gravity-driven flow of surfactant-laden liquid film over a rod is examined in creeping flow limit in presence of an applied shear stress at gas–liquid (GL) interface. This flow system admits two instability modes: (i) a surface-tension driven Rayleigh-Plateau (RP) mode, and (ii) a surface-tension gradient driven surfactant mode. In absence of imposed shear stress, the surfactant completely suppresses the RP instability when Marangoni number (Ma), increases above a critical value. On further increase of Ma to high enough values, the surfactant mode becomes unstable, and as a result, a gap in terms of Ma exists where the film flow remains stable. The present work shows that these stability characteristics are dramatically modified in presence of imposed shear stress. When shear stress acts in a direction to assist gravity-driven flow (i.e. positive stress), it has a stabilizing effect on RP mode in addition to the stabilizing effect of surfactant. In contrast, the positive applied shear destabilizes the surfactant mode when shear stress exceeds above a critical value. Below this critical stress value, it is still possible to obtain stable film flow for a range of Marangoni number values. However, above this critical value, the shear stress induced surfactant mode instability engulf whole region from low wave number to finite wave number perturbations for any value of Ma. For negative values of imposed shear (i.e. when shear stress acts opposite to gravity-driven flow direction), the effect of shear stress on RP mode is destabilizing (stabilizing) when the magnitude of applied stress is lower (higher) than a threshold value. On the other hand, the effect of applied negative shear is found to be exactly opposite for surfactant mode. The overall analysis of results for negative shear shows that it is not possible to obtain stable flows when magnitude of shear stress is above a certain value in a similar manner as shown for positive applied stress. It was also observed that the finite wave number perturbations become important for a wide range of parameters for shear stress induced destabilization of film flow configuration. This was not the case in absence of applied stress in which case the dominant perturbations were always long wavelength perturbations.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"111 ","pages":"Pages 229-243"},"PeriodicalIF":2.5,"publicationDate":"2025-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143093478","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":"Joule heating and entropy generation on AC electroosmotic flow of Jeffrey fluid in a slowly varying micro-channel","authors":"N.K. Ranjit ,&nbsp;G.C. Shit","doi":"10.1016/j.euromechflu.2025.01.004","DOIUrl":"10.1016/j.euromechflu.2025.01.004","url":null,"abstract":"<div><div>In this paper, we examine the impact of joule heating and entropy generation on a time-periodic electroosmotic flow of viscoelastic fluids in a slowly varying microchannel under the influence of a magnetic field. We consider the Jeffrey fluid model, which describes the linear viscoelastic fluid, and an effort is made to obtain the analytical solutions, considering velocity and thermal slip conditions at the fluid–solid interface. The study reveals that the relaxation and retardation times in the Jeffrey fluid have a significant effect on the axial velocity and temperature distribution within the microchannel. Further, we observed that the Joule heating contributes to enhanced thermal response in both temperature distribution and Nusselt number, leading to increased entropy generation. The Bejan number profiles enhance with an increase in the Joule heating parameter due to the conversion of electrical energy into thermal energy. The velocity slip enhances the rate of heat transfer and entropy generation, while these quantities decrease with the thermal slip. The present study on AC electroosmosis and electrothermal flow shows significant promise as a fluid-driven technique in microfluidics for future endeavors.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"111 ","pages":"Pages 176-187"},"PeriodicalIF":2.5,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143093481","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 wind tunnel experimental investigation for the flow normal to a flat plate attached with a closed membrane coating","authors":"Yakun Zhao ,&nbsp;Huanyu Zhang ,&nbsp;Shuyue Sun ,&nbsp;Tao Peng ,&nbsp;Gang Chen ,&nbsp;Xinliang Tian","doi":"10.1016/j.euromechflu.2025.01.002","DOIUrl":"10.1016/j.euromechflu.2025.01.002","url":null,"abstract":"<div><div>Wind tunnel experiments were conducted to study the flow normal to a flat plate attached with a closed flexible membrane. Two control parameters, the membrane width and the wind speed, were considered. A suspension device was designed to measure the aerodynamic forces exerted on the plate+membrane system. Experimental results show that, contingent on the membrane width, a significant drag reduction up to 22.2% is reported. Based on image recognition techniques, a measurement method using two high-speed cameras was developed to reconstruct the membrane’s motion. The time-averaged shape of the membrane is maintained as a plump D-shape cylinder. The membrane exhibits a rigid-body flapping motion and a bending deformation, accompanied by traveling waves along the membrane. Results of amplitude and standard deviation of the membrane motion show that the more intense flapping occurs on two sides of the membrane, while gentler flapping in the middle region. Furthermore, smoke-wire flow visualization reveals that the presence of the membrane significantly alters the flow structures in the delay in flow separation and the emergence of narrower wake structures, thus reducing drag. Our study demonstrates that such a flow control device using a flexible membrane coating is effective under 3D, high <span><math><mrow><mi>R</mi><mi>e</mi></mrow></math></span> and turbulent flow conditions, which providing powerful evidence of its potential for practical engineering applications.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"111 ","pages":"Pages 127-142"},"PeriodicalIF":2.5,"publicationDate":"2025-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143093519","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 on post-collapse rebound and rebound-induced pulsations of hydraulic cavitation in a Venturi","authors":"Liang Fang ,&nbsp;Xiaogang Xu ,&nbsp;Mao Lei ,&nbsp;Qiang Li ,&nbsp;Zhenbo Wang","doi":"10.1016/j.euromechflu.2025.01.003","DOIUrl":"10.1016/j.euromechflu.2025.01.003","url":null,"abstract":"<div><div>High-frequency and high-amplitude pulsation characteristics play a significant role in the various negative effects of hydraulic cavitation, but the formation mechanism has not been explored clearly. Addressing this problem, experimental and numerical studies on internal cavitation flow, represented by Venturi cavitation, were conducted. Through high-speed photography and image processing, post-collapse rebound, a rarely reported hydraulic cavitation evolutionary link was demonstrated. Based on a self-developed simplified compressible cavitation algorithm, the evolution and formation of rebound were analyzed, and the formation mechanism of high-frequency and high-amplitude pressure pulsation was further revealed. Also, the effects of compressibility and pressure ratio were studied. The results show that reciprocating rebounds occur after the detached cavity collapses, with the rebound cavity volume successive decreasing. Rebound is the result of pressure wave propagation. The propagation of the cavity collapse-induced peak pressure tends to develop a trough pressure low to saturated vapor pressure, resulting in the post-collapse rebound. Reciprocating rebounds and collapse are key links causing strong cavitation pulsations, especially high-frequency and high-amplitude pulsations. The collapse of the detached cavity and reciprocal rebound cavities within a single evolutionary cycle induced extremely high pressure and multiple high pressures successively, forming the high-frequency and high-amplitude pressure pulsation. Besides, compressibility is the key to the numerical prediction of rebound. The number of rebounds and the volume of the rebound cavity depend on the severity of cavitation.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"111 ","pages":"Pages 143-161"},"PeriodicalIF":2.5,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143093483","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 of vortex shedding phenomenon induced by various bluff body geometries for use in vortex flowmeters","authors":"Saeed Farsad ,&nbsp;Seyed Morteza Parpanchi ,&nbsp;Mojtaba Rezaei","doi":"10.1016/j.euromechflu.2025.01.007","DOIUrl":"10.1016/j.euromechflu.2025.01.007","url":null,"abstract":"<div><div>Studying and understanding the vortex-shedding phenomenon in the wake region of bluff bodies is crucial in most fluid systems. This paper uses wind tunnel experiments to evaluate and assess the downstream flow of five bluff body models with various geometric shapes, including triangle, rectangle, square, trapezoid, and T-shape. The aim is to utilize these shapes in flowmeters and angle sensors (as a novel innovation). The velocity field, turbulence intensity, and vortex shedding frequency of the downstream airflow around these models were examined at different flow angles. Results indicate that rectangular and trapezoidal bluff bodies are more suitable for application in flow angle sensors using vortex than other geometries studied. Based on the results, recommend the T-shaped model over other geometries for use in vortex flow meters. Furthermore, the rectangular bluff body at a 107.5° angle provides the most suitable areas for observing vortices and measuring or calibrating hot-wire anemometer probes.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"111 ","pages":"Pages 188-200"},"PeriodicalIF":2.5,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143093482","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":"Reconfiguration and drag reduction of flexible beam with point buoyancy in oscillatory flow","authors":"Jixiang Song ,&nbsp;Weimin Chen ,&nbsp;Dingbang Yan ,&nbsp;Shuangxi Guo","doi":"10.1016/j.euromechflu.2025.01.006","DOIUrl":"10.1016/j.euromechflu.2025.01.006","url":null,"abstract":"<div><div>Flexible structures with point buoyancy widely exist in nature and engineering. Under the action of oscillating flow, it usually has a large geometric nonlinear dynamic response. However, the dynamic response and drag reduction of flexible structures with point buoyancy have not been studied. Therefore, the numerical method in this paper investigates the dynamic response and drag reduction of point buoyant flexible structures under oscillatory flow. Firstly, complex spatial curvilinear coordinates establish the dynamic partial differential equations of flexible structures with point buoyancy. Then, the implicit finite-difference time-domain method is used to discretize the partial differential equation in space and time to form an algebraic equation. Finally, the dynamic response and drag reduction of flexible structures under non-buoyancy, uniform buoyancy, and point buoyancy are numerically analyzed. The results show that with the increase of Cauchy number <em>C</em>_<em>Y</em>, the deformation of the flexible structure becomes larger and larger, and a local bending point appears. The dimensionless vibration frequency numbers explain the occurrence of local bending points. Unlike no buoyancy, uniform buoyancy and point buoyancy make the flexible structure smaller and more symmetrical. Uniform buoyancy and point buoyancy can increase the Reconfiguration number <em>R</em>. The greater the buoyancy and buoyancy position, the greater the Reconfiguration number <em>R</em>. The load on the flexible structure under oscillating flow is still less than that on the rigid structure. The Vogel exponent is calculated by fitting the Reconfiguration number <em>R</em>. The drag reduction is directly proportional to the Vogel exponent <em>v</em>, that is, the greater the Vogel exponent <em>v</em>, the greater the drag reduction. When the Cauchy number <em>C</em>_<em>Y</em> is large, the Vogel exponent <em>v</em> of uniform buoyancy and point buoyancy is smaller than that of non-buoyancy. The greater the point buoyancy and buoyancy position, the smaller the deformation of the flexible structure, the greater the Reconfiguration number <em>R</em>, and the greater the Vogel exponent <em>v</em>. When the buoyancy position is small, the influence of point buoyancy on the flexible structure can be ignored.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"111 ","pages":"Pages 162-175"},"PeriodicalIF":2.5,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143093484","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":"Dispersion - erosion coupling in landslide","authors":"Bekha Ratna Dangol ,&nbsp;Jeevan Kafle ,&nbsp;Shiva P. Pudasaini","doi":"10.1016/j.euromechflu.2024.12.008","DOIUrl":"10.1016/j.euromechflu.2024.12.008","url":null,"abstract":"<div><div>Non-hydrostatic dispersive models can better describe the landslide motion. Following a dispersive wave equation and a mechanical erosion model for mass flows, here, we develop a novel dynamically coupled dispersion–erosion wave model that combines these two very essential complex processes. The newly developed model for landslide recovers the classical dispersive water waves and dispersive wave equation for landslide as special cases. We present several exact analytical solutions for the coupled dispersion–erosion model. These solutions are constructed for the time and spatial evolution of the flow depth. Solutions reveal that the dispersion and erosion are strongly coupled as they synchronously control the landslide dynamics. The results show that the wave dispersive wave amplifies with the increasing particle concentration, decreasing earth pressure, higher gravitational acceleration, increased slope angle and increased basal friction. The important novel understanding is that the intensity of the dispersive wave increases when erosion and dispersion are coupled. The results indicate the essence of proper selection of the initial and boundary conditions while solving applied and engineering problems associated with the dispersive<!--> <!-->-<!--> <!-->erosive mass transport. This provides the foundation for our understanding of the complex dispersion and erosion processes and their interplay.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"111 ","pages":"Pages 201-214"},"PeriodicalIF":2.5,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143093480","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}