Experiments in Fluids最新文献

{"title":"Photogrammetry for three-dimensional particle image velocimetry","authors":"Tianshu Liu,&nbsp;David M. Salazar,&nbsp;Yun Liu,&nbsp;Zhenyu Zang,&nbsp;Shizhao Wang","doi":"10.1007/s00348-026-04259-2","DOIUrl":"10.1007/s00348-026-04259-2","url":null,"abstract":"<div><p>This paper describes photogrammetric reconstruction of a three-dimensional (3D) velocity field from multiple particle images taken by cameras with different positions and orientations based on integration of the multiple-camera photogrammetry and the optical flow method. The main technical aspects include photogrammetric camera calibration to establish the local object-space frame associated with a camera and the point-correspondence between particle images taken by multiple cameras. The least-squares solution of an overdetermined linear system of the projection equations gives an explicit linear transform from the optical flow in the image plane to a 3D velocity in the object space for reconstruction of a 3D velocity field from the optical flow fields. The error analysis of the proposed method is given and the major error sources are identified. The use of this method is demonstrated in simulations of a vortex jet and a vortex ring to evaluate the effects of the measurement domain depth, particle density, particle size and overlapped particles on the total error of the reconstructed 3D velocity fields. Further, this method is applied to experiments to reconstruct the 3D time-averaged velocity fields of an underwater jet and an air flow over a delta wing.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"67 7","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148380597","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":"Aerodynamic characterization of an isolated rotating wheel in ground contact using dual-balance measurements","authors":"Fengli Zhang,&nbsp;Wei Yi,&nbsp;Wenjiang Wang,&nbsp;Qiuli Luo,&nbsp;Rongrong Zhang,&nbsp;Xianzhong He,&nbsp;Qingyang Wang,&nbsp;Shunlin Tang","doi":"10.1007/s00348-026-04260-9","DOIUrl":"10.1007/s00348-026-04260-9","url":null,"abstract":"<div><p>In this study, the aerodynamic characteristics of a full-scale, isolated passenger car wheel equipped with three rim configurations—a five-spoke rim, an aerodynamic rim, and a closed rim—were experimentally investigated in a wind tunnel. A dual-balance system was developed to measure the drag, lift, and side force of the wheel. The wake flow behind the wheel was assessed using a 14-hole pressure probe. The numerical simulation was employed to assist in analyzing the aerodynamic flow phenomena underlying the observed forces. The results indicated that the drag coefficients for the aerodynamic and closed rim configurations decreased by approximately 10<span>(%)</span> as the Reynolds number increased from 7.8 <span>(times )</span> <span>(10^{5})</span> to 1.56 <span>(times )</span> <span>(10^{6})</span>, whereas the coefficient for the five-spoke rim setup remained nearly constant. Additionally, drag measurements obtained using the dual-balance system were approximately 8<span>(%)</span> lower than those recorded with a single-balance setup. Furthermore, the difference in drag between different rim configurations significantly increased with increasing wheel yaw angles. Notably, the closed rim design exhibited 15.2<span>(%)</span> less drag than the five-spoke rim at a 0<span>(^{circ })</span> yaw angle and 48.2<span>(%)</span> less drag at a 20<span>(^{circ })</span> yaw angle.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"67 7","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148380545","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":"Controlled accelerations for Rayleigh–Taylor instability","authors":"J. T. Horne-Jones,&nbsp;D. J. Glinnan,&nbsp;A. G. W. Lawrie,&nbsp;R. J. R. Williams","doi":"10.1007/s00348-026-04249-4","DOIUrl":"10.1007/s00348-026-04249-4","url":null,"abstract":"<div><p>The dynamics of turbulent mixing induced by Rayleigh–Taylor instability are heavily dependent on the acceleration experienced by the fluids and the frequency content of the initial interface between them. Both are readily controllable in numerical simulations, but in experimental studies are difficult to influence and adequately diagnose. In this paper, we present the CAMPI (<b>C</b>ontrolled <b>A</b>cceleration for <b>M</b>ulti-<b>P</b>hase <b>I</b>nstabilities) apparatus, an experimental facility for study of low Atwood number Rayleigh–Taylor instability with highly controllable, complex acceleration histories. The apparatus provides unique and novel capability for the experimental study of variable acceleration Rayleigh–Taylor instability with fully miscible fluids and at a scale suitable for high-resolution optical diagnostics. We present experimental results of initially single-mode instability evolution through two stepwise acceleration reversals, a case termed Accel-Decel-Accel, demonstrating the ability of the apparatus to accurately generate a prescribed acceleration history. We observe the behaviour predicted by previous numerical studies, with instability growth reaching a terminal velocity in the first episode of acceleration, followed by a shrinking and homogenisation of the mixing region throughout deceleration, and unstable growth from a multi-frequency initial condition during the second acceleration. We present the CAMPI apparatus to the field as a much needed resource of ground truth data on the behaviour of Rayleigh–Taylor instability across a broad range of regimes. UK Ministry of Defence © Crown Owned Copyright 2026/AWE.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"67 7","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-026-04249-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148380215","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":"Visualization of bubble dynamics in biomimetic leaf-inspired flow channels during alkaline water electrolysis","authors":"Ziqing Wang,&nbsp;Ying Wang,&nbsp;Luhaibo Zhao,&nbsp;Qianqian Chen,&nbsp;Zhiyong Tang","doi":"10.1007/s00348-026-04248-5","DOIUrl":"10.1007/s00348-026-04248-5","url":null,"abstract":"<div><p>A visualized experimental study was conducted to elucidate multiscale bubble dynamics in a biomimetic leaf-inspired flow channel during alkaline water electrolysis. Using high-speed imaging, bubble behaviors across hierarchical channels and on the nickel mesh electrode were quantitatively analyzed. The results reveal a synergistic function among channels: the main channel drives fluid circulation and bubble discharge, the secondary channel transports large coalesced bubbles, and the refined channel promotes bubble growth and merging. As the electrolyte temperature increased from 40 to 80 °C, the average bubble velocity rose from 0.50 to 0.84 µm·s⁻¹, while the mean detachment time decreased from 35 to 8 s. The detachment diameter converged near 300 µm. These results indicate that elevated temperatures reduce viscosity and surface tension, accelerating bubble evolution and homogenizing detachment. The hierarchical biomimetic flow channel enhances gas evacuation, providing quantitative insights for optimizing mass transfer and structural design in high-efficiency alkaline electrolyzers.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"67 7","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148380589","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 event-based vision sensor cameras for measuring bubbly flow characteristics","authors":"Ahmed Al Brahim,&nbsp;Kuppuraj Rajamanickam,&nbsp;A. M. K. P. Taylor,&nbsp;Yannis Hardalupas","doi":"10.1007/s00348-026-04272-5","DOIUrl":"10.1007/s00348-026-04272-5","url":null,"abstract":"<div><p>In this study, the capability of Event-based Vision Sensor (EVS) cameras for measuring simultaneously bubble motion, size, and shape in complex bubbly flows has been assessed. This assessment initially focused on benchmark evaluation of the accuracy of an EVS camera in tracking the motion and size of precisely manufactured naturally buoyant particles in quiescent water. Experiments were carried out in synchronization with a conventional high-speed (HS) camera, enabling quantitative comparison. The synchronized measurements obtained from both cameras agreed well with differences of less than 0.65% in measured particle velocities and 2.4% in measured diameters, demonstrating the EVS camera’s capability to precisely measure motion and dimensions. Following this validation, the assessment expanded to characterize bubbles generated by injecting compressed air at various pressures at the bottom of a quiescent water tank. The EVS camera demonstrated comparable performance to the HS camera in measuring bubble size and velocity at low to moderate injection pressures. The bubble tracks uniquely captured by the EVS camera, due to its adjustable accumulation time, can be leveraged to extract trajectory and velocity information, as well as instances of partial bubble visual overlap in the camera view. However, event saturation is observed at the EVS camera for several events generated by bubble motion that surpasses a critical threshold (e.g., dense bubbly flow). Subsequently, the increased latency at both pixel levels and read-out leads to temporal misalignment relative to the flow bubble dynamics. This challenge was addressed by employing a pulsed illumination source, which allowed the camera to capture dense bubbly flows, as the increased presence of bubbles corresponds to a reduced number of EVS recorded events. Overall, the assessment highlights that EVS cameras offer comparable performance to conventional HS cameras in characterising bubbly flows with two additional unique advantages. (i) Ability to record bubble tracks, which can be directly used for bubble velocimetry. (ii) An instantaneous EVS camera image records events at a significantly reduced data rate, which enables real-time bubble EVS imaging at higher speeds than conventional HS cameras.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"67 7","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-026-04272-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148380770","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":"Wind flow modifications induced by different configurations of vegetative barriers: a wind tunnel study","authors":"Jamily F. Stocco,&nbsp;Frédéric Murzyn,&nbsp;Jean-Luc Harion,&nbsp;Bruno Furieri,&nbsp;Jane M. Santos","doi":"10.1007/s00348-026-04266-3","DOIUrl":"10.1007/s00348-026-04266-3","url":null,"abstract":"<div><p>Vegetative barriers are commonly used to reduce wind velocity and mitigate dust dispersion and aeolian erosion. While their effectiveness has been widely demonstrated, the influence of plant spatial arrangement—particularly in multi-row configurations with varying heights—remains underexplored. This study presents a wind tunnel investigation of airflow modification by artificial vegetation models arranged in three configurations: a single row of trees and two multi-row layouts combining trees and shrubs (MR1: trees upstream and shrubs downstream; and MR2: shrubs upstream and trees downstream). Based on 2D laser Doppler velocimetry measurements, both streamwise (<i>U</i>) and vertical (<i>V</i>) components together with Reynolds shear stress (<span>(overline{u'v'})</span>) were analyzed to study the wake dynamics. The results show that MR1 (trees upstream) induces a more intense velocity reduction near the barrier, with 28% of the downstream area exhibiting a reduction in the streamwise velocity greater than 60%, and the mean reduction of the streamwise velocity is 57%, indicating stronger near-surface sheltering. In contrast, MR2 (shrubs upstream) promotes a smoother and more extended velocity recovery profile, with a mean reduction of streamwise velocity of 46%, favoring long-range mitigation. Despite having similar porosity, the vertical distribution of solid elements in MR1 increases the effective frontal blockage, enhancing aerodynamic resistance and flow deceleration. Turbulence analysis revealed that MR1 concentrates Reynolds shear stress near the ground, while MR2 shifts turbulent activity upward due to its vertical distribution of vegetation. These findings emphasize the role of barrier structure in shaping airflow patterns and provide experimental data for validating numerical models. The results contribute to the design of more efficient windbreak strategies adapted to specific environmental goals, such as erosion control or dust dispersion mitigation. They shed new light on the influence of the upstream–downstream distribution of vegetation heights.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"67 7","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-026-04266-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148380771","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":"Simultaneous free-surface and 3D flow measurements of a vortex ring in head-on collision with the air–water interface","authors":"Yukun Han,&nbsp;Jinho Oh,&nbsp;Chong Pan,&nbsp;Sang Youl Yoon,&nbsp;Kyung Chun Kim","doi":"10.1007/s00348-026-04256-5","DOIUrl":"10.1007/s00348-026-04256-5","url":null,"abstract":"<p>Simultaneous measurement of free-surface deformation and subsurface velocity field is essential for quantitative investigation of vortex–surface interaction, but remains difficult because optical interference near the interface contaminates underwater volumetric velocimetry. In the present study, a simultaneous measurement framework is established for resolving free-surface deformation and subsurface vortex evolution during the head-on impact of a vortex ring (<span>(Re_{Gamma }=2509)</span>) with an air–water interface. Stereoscopic surface measurement and four-dimensional particle tracking velocimetry (4D-PTV) are integrated within a common spatial coordinate system and synchronized time base, enabling time-resolved capture of the coupled interface and subsurface flow dynamics. The feasibility of the system relies on three strategies: dual illumination with optical filtering to separate free-surface and underwater particle images, short-time-window background subtraction to suppress surface reflection, and temporal continuity in Lagrangian tracking to identify valid underwater particle trajectories. The synchronized measurements resolve the full interaction process and quantify the vortex–surface response in different evolution stages through circulation, kinetic energy within the vortex core region, and free-surface energy evolution. The dataset quality is supported by three independent checks: a kinematic boundary condition residual sharply concentrated near zero, with a three-sigma level of 0.65% of the characteristic vortex velocity; a stress-free-consistency indicator that remains low overall, with localized peaks restricted to strong vortex–surface interaction regions; and a correlation-based time lag analysis showing physically consistent upward propagation of vortex-induced disturbances before direct impact. The present framework therefore provides an experimental solution for linking subsurface vortical dynamics to free-surface response in a time-resolved and spatially registered manner.</p>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"67 7","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148323905","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 gravity currents flowing on heated walls","authors":"Stefano Lanzini,&nbsp;Massimo Marro,&nbsp;Mathieu Creyssels,&nbsp;Alexandre Azouzi,&nbsp;Pietro Salizzoni","doi":"10.1007/s00348-026-04238-7","DOIUrl":"10.1007/s00348-026-04238-7","url":null,"abstract":"<div><p>We present an experimental study on steady gravity currents advancing along a heated wall. The study aims to assess how the structure and dynamics of a wall-heated current are modified with respect to the adiabatic-wall case. The current is generated by a mixture of air and carbon dioxide continuously supplied at the channel inlet. To have a complete point-wise characterization of the flow, simultaneous high-frequency measurements of two velocity components, CO<span>(_2)</span> concentration, and temperature are performed. An experimental protocol is presented to reconstruct the local fluid density and to estimate vertical and horizontal turbulent fluxes of CO<span>(_2)</span>, temperature, and buoyancy. The reliability of both the flow measurements and of the estimate of convective heat flux exchanged at the wall is assessed through integral balances of CO<span>(_2)</span> mass, enthalpy, and buoyancy, performed at different distances from the source. In the heated experiments, a convectively unstable boundary layer forms near the wall, capped by a stably stratified region. The influence of this condition on the first- and second-order flow statistics profiles is examined. With respect to the adiabatic case, the floor heating induces a rise in the wall drag, a reduction in the maximum flow velocity, and a thickening of the gravity current region characterized by a nearly constant velocity. In contrast, the vertical height of the mixing zone, characterized by an almost-constant vertical gradient of the streamwise velocity, does not exhibit a clear dependence on heating intensity.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"67 7","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-026-04238-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148323190","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":"Flow speed analysis of transparent plasma flows using an event-based camera","authors":"Martin Eberhart,&nbsp;David Leiser,&nbsp;David Steuer,&nbsp;Stefan Loehle","doi":"10.1007/s00348-026-04254-7","DOIUrl":"10.1007/s00348-026-04254-7","url":null,"abstract":"<div><p>Established optical techniques for measuring plasma flow speeds, for example Fabry–Pérot interferometry (FPI), are challenging due to the need for accurate alignment and complex data acquisition and evaluation. As a novel alternative, we propose using an event-based camera to determine velocities in a transparent, particle-free plasma jet by tracing the flow of radiating flow features across the field of view. The potential of this new technique is assessed by studying a fast hydrogen-helium plasma flow in an arcjet-driven facility. Data analysis yields temporally and spatially resolved axial velocities. The determined axial velocity profile qualitatively matches the observed supersonic flow structure and ranges between 8 and 20 km/s. For a given position, flow speeds vary by about ±3 km/s, which is either attributed to measurement uncertainties or to actual variations. The mean values compare well to FPI measurements.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"67 7","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-026-04254-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148281732","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":"Experimental investigation of shear layer and wall region responses to three-dimensional obstacles in steady density currents","authors":"Jingyao Chen,&nbsp;Yanan Chen,&nbsp;Benjamin Kneller,&nbsp;Dongrui Han,&nbsp;Eckart Meiburg,&nbsp;Zhiguo He","doi":"10.1007/s00348-026-04258-3","DOIUrl":"10.1007/s00348-026-04258-3","url":null,"abstract":"<div><p>This study investigates the structural responses of shear layers and wall regions to three-dimensional obstacles of varying heights in continuous-inflow density currents. A custom-designed particle image velocimetry (PIV) system was employed to capture quasi-three-dimensional flow structures and reduce the inter-run variability inherent in traditional multi-section measurements. An optimized two-stage diffuser was used to ensure uniform spanwise inflow and prevent lateral momentum errors. This configuration enabled separate examination of plumes and underflows, revealing distinct dynamic behaviors. Results show two distinct response regimes. Plumes, consisting solely of a shear layer, consistently responded via efficient lateral bypassing, a mechanism that remained dominant even for obstacles in the low-profile regime where overtopping was easier. In contrast, underflows, featuring a wall region, were consistently dominated by upstream blockage and vertical deflection, with lateral bypassing remaining suppressed even for obstacles that created the most substantial lateral pressure gradients in the protruding case. Flow thickness analysis corroborates these distinct patterns. In the plume cases, obstacles force the central flow to bypass laterally, thinning the downstream layer and leading to a thinner and faster layer downstream of the obstacle. Underflows, however, exhibit increased thickness near the centerline due to upward fluid displacement from the wall region, with minimal spanwise redistribution. Turbulence intensity patterns also underscore these differences: plumes display peaks in areas of lateral flow diversion and downstream convergence, whereas underflows show high turbulence where upward-deflected wall region flow enters the shear layer.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"67 7","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148281731","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}