Experiments in Fluids最新文献

{"title":"A contribution to 3D tracking of deformable bubbles in swarms using temporal information","authors":"Lantian Wang,&nbsp;Tian Ma,&nbsp;Dirk Lucas,&nbsp;Kerstin Eckert,&nbsp;Hendrik Hessenkemper","doi":"10.1007/s00348-025-03963-9","DOIUrl":"10.1007/s00348-025-03963-9","url":null,"abstract":"<p>Reliable Lagrangian 3D tracking of individual bubble swarm members allows a deeper understanding of hydrodynamic bubble–bubble interactions and their collective rise. For multi-view measurements, we have recently developed such a tracking method (Hessenkemper in Int J Multiph Flow 179:104932, 2024), which is able to track deformable bubbles with low to moderate view obstruction through the bubbles to each other. In the present work, we aim to further enhance the 3D tracking performance by additionally incorporating 2D temporal information in the form of previously established 2D tracks in each camera view. The new 3D tracking method is able to disambiguate cross-view object associations at each time step by using the 2D track information accumulated over time. In addition, the temporal information from multiple 2D domains is used in two post-processing steps to improve the completeness of established 3D trajectories. Compared to the previous 3D tracking method, the extended 3D tracking framework shows noticeable improvements in tracking ability, accuracy, and completeness of trajectories.</p>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 2","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-025-03963-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143109451","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":"A large test section low-speed water tunnel in a small package","authors":"Sean Devey,&nbsp;Morteza Gharib","doi":"10.1007/s00348-025-03959-5","DOIUrl":"10.1007/s00348-025-03959-5","url":null,"abstract":"<div><p>A novel type of low-speed water tunnel has been designed which uses an array of submersible electric thrusters to propel water through a test section centered within a large rectangular tank. This design can operate as a suction or blowdown tunnel to alternately create uniform, low-turbulence flow or spatially and temporally varying flows such as shear layers, wakes, and gusts. The thruster array architecture also enables an order of magnitude improvement in tunnel footprint for a given test section size, eschewing the need for bulky traditional elements such as the contraction, turning, and settling chambers. Planar digital particle image velocimetry (DPIV) and single-component constant temperature anemometry (CTA) measurements of flow uniformity and turbulence intensity indicate comparable flow quality to larger traditional tunnels when operated in suction mode. Dye visualizations of low Reynolds number cylinder wake flows are also presented to demonstrate tunnel capabilities.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 2","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143109659","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":"The aerodynamics of sharp- and filet-edged cylinders in high supersonic flow","authors":"Travis A. Duchene,&nbsp;Stuart J. Laurence","doi":"10.1007/s00348-025-03968-4","DOIUrl":"10.1007/s00348-025-03968-4","url":null,"abstract":"<p>To develop a physical understanding and accurate trajectory models for atmospheric re-entry objects like space debris, the influence of the flight attitude on the aerodynamic coefficients of cylindrical bodies in high-speed flow is of interest. Experiments were conducted in a Mach-4 Ludwieg tube at The University of Maryland to study the aerodynamics of cylinders with varying aspect ratios and edge sharpness. A free-flight technique with a high-speed object tracking apparatus was used that allows unconstrained model motion, free of any sting interference, over a full range of angle of attack. A piece-wise analytic function for the model outline combined with a subpixel edge-detection routine allowed measurements of the aerodynamic coefficients based on the 4-degrees-of-freedom model motion. Experimental results were compared to modified Newtonian flow solutions, with generally good agreement. The influence of the angle of attack on the aerodynamic loading was determined to vary strongly according to the aspect ratio and edge radius. In the case of sharp-edged cylinders, increasing the aspect ratio led to an increase in both the flight region for positive lift and larger regions of static stability. By adding curvature to the cylinder base edges, the location of the statically stable trim points occurs at the fully base-exposed and fully body-exposed orientations. It was also found that the flight attitude region for which the cylinder was statically stable was expanded due to the addition of edge curvature. Further, as the aspect ratio was increased for these filet-edged cylinders, the magnitude of the moment coefficient increased noticeably.</p>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 2","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143109425","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":"Dynamic wall shear stress measurement using event-based 3d particle tracking","authors":"Christian E. Willert,&nbsp;Joachim Klinner","doi":"10.1007/s00348-024-03946-2","DOIUrl":"10.1007/s00348-024-03946-2","url":null,"abstract":"<div><p>We describe the implementation of a 3d Lagrangian particle tracking (LPT) system based on event-based vision (EBV) and demonstrate its application for the near-wall characterization of a turbulent boundary layer (TBL) in air. The viscous sublayer of the TBL is illuminated by a thin light sheet that grazes the surface of a thin glass window inserted into the wind tunnel wall. The data simultaneously captured by three synchronized event cameras are used to reconstruct the 3d particle tracks within <span>(400,upmu text{m})</span> of the wall on a field of view of <span>(12.0,text{mm} times 7.5,text{mm})</span>. The velocity and position of particles within the viscous sublayer permit the estimation of the local vector of the unsteady wall shear stress (WSS) under the assumption of linearity between particle velocity and WSS. Thereby, time-evolving maps of the unsteady WSS and higher-order statistics are obtained that are in agreement with DNS data at matching Reynolds number. Near-wall particle acceleration provides the rate of change of the WSS which exhibits fully symmetric log-normal superstatistics. Two-point correlations of the randomly spaced WSS data are obtained by a bin-averaging approach and reveal information on the spacing of near-wall streaks. The employed compact EBV hardware coupled with suited LPT tracking algorithms provides data quality on par with currently used, considerably more expensive, high-speed framing cameras.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 2","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03946-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143109303","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":"Study on the movement behavior of ping-pong ball on water surface under microgravity","authors":"Yi fan Zhao,&nbsp;Shu yang Chen,&nbsp;Di Wu,&nbsp;Liang Hu,&nbsp;Li Duan,&nbsp;Qi Kang","doi":"10.1007/s00348-024-03952-4","DOIUrl":"10.1007/s00348-024-03952-4","url":null,"abstract":"<div><p>In a microgravity environment, where gravity is almost absent, surface tension plays a dominant role in the behavior of fluid motion. The motion of fluids within storage tanks can lead to significant oscillations of the tank itself or even the entire vehicle, posing substantial safety risks. Solid foam particle anti-sloshing technology represents a novel research topic in addressing this issue. The anti-sloshing technology using solid foam particles is a novel research topic. In this experiment, ping-pong balls were used to simulate individual foam particles, and a transparent liquid tank was designed to observe their motion. Two different hydrophobic materials were applied to the surface of the balls to alter their surface tension in water. A drop tower was used to create a microgravity environment, and the motion of the balls in water under microgravity was recorded with a camera. Both static and dynamic analyses were conducted on the balls under normal gravity and microgravity conditions, considering water resistance, surface tension, and added mass forces. The control equations for the position and velocity of the ball’s center of mass were derived. The experimental results showed that under microgravity, hydrophilic balls tend to submerge into the water, while hydrophobic balls move upwards, away from the water surface. The equilibrium adsorption position of the hydrophilic balls differed significantly between microgravity and normal gravity conditions, with noticeable oscillatory movement in the vertical direction. The experimental results showed good agreement with the dynamic model.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 2","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143109304","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":"Heat transfer visualization of transitional growth of turbulent spot on a wedge in Mach 5.2 hypersonic flow using fast-response TSP","authors":"Kosuke Yoshikawa,&nbsp;Hiroshi Ozawa","doi":"10.1007/s00348-025-03964-8","DOIUrl":"10.1007/s00348-025-03964-8","url":null,"abstract":"<div><p>In the present study, the propagation velocity and lateral spreading angle of turbulent spots on a wedge in transient hypersonic boundary layer flows were investigated and characterized by measuring the heat flux distribution using a fast-response temperature-sensitive paint (TSP) in a shock tunnel facility. The shock tunnel was operated under the over-tailored condition and provided with the low- to high-unit Reynolds number during a test duration, which was realized by the contact surface arrival in the shock tube that changed the temperature and density of the reservoir gas. Power spectral density estimated from the pressure recordings may indicate that the boundary layer flow was transitional. In TSP measurements, the global heat flux distribution on the wedge was accurately obtained qualitatively. Surprisingly, turbulent spots were visualized using TSP for each unit Reynolds number condition. The propagation velocities at the head, peak heat flux point, and tail of turbulent spots for low- and high-unit Reynolds number conditions were approximated from the TSP images to be 87 ~ 96%, 69 ~ 73%, and 52 ~ 57% of the boundary layer edge velocities at each condition, respectively. These results were in good agreement with the available data in previous investigations. The lateral spreading angle of turbulent spots was also measured to be 5° ~ 10° from the TSP images. This study showed that the fast-response TSP had the ability to visualize the temporally resolved turbulent spots by measuring the heat flux on the wedge.</p><h3>Graphical abstract</h3>\u0000<div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 2","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143109302","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":"Ghost particle suppression multiplicative algebraic reconstruction technique for tomographic PIV","authors":"Peng Lei,&nbsp;Hua Yang,&nbsp;Zhouping Yin,&nbsp;Feng Shan","doi":"10.1007/s00348-024-03935-5","DOIUrl":"10.1007/s00348-024-03935-5","url":null,"abstract":"<p>The exponential distribution law of the intensity of tomographic particle image velocimetry (Tomo-PIV) reconstructed particles is validated through a probabilistic approach. Moreover, a new Tomo-PIV particle reconstruction method is proposed based on the intensity distribution law of ghost particles and the self-similarity of true particles. In this method, ghost particles are treated as reconstruction noise. Furthermore, a combination of the variational denoising method and the inverse diffusion equation with a regularization constraint is used to suppress ghost particles. This method is called the ghost particle suppression multiplicative algebraic reconstruction technique (GS-MART). The proposed algorithm was evaluated numerically on cylindrical wake simulation data, and the reconstruction quality, intensity distribution of true particles and ghost particles, and velocity calculation accuracy were analyzed under different particle densities. To validate the effectiveness of GS-MART in real flow field measurement applications, we conducted an experiment on jet flow. The findings demonstrated that the high-precision 3D particle reconstruction achieved by GS-MART significantly enhanced the accuracy of the velocity field estimation.</p>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 2","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143109078","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":"Comparison of displacement estimation techniques for background-oriented schlieren of high-speed compressible turbulent flows","authors":"Tanbo Zhou,&nbsp;Jonathan Gaskins,&nbsp;Jonathan Poggie,&nbsp;Sally P. M. Bane","doi":"10.1007/s00348-024-03944-4","DOIUrl":"10.1007/s00348-024-03944-4","url":null,"abstract":"<div><p>Background-oriented schlieren (BOS) is a non-intrusive optical method for measuring density gradients in a fluid flow based on changes of local refractive index. The density gradients can be obtained by observing the displacement between two images of a background pattern, with and without the presence of the flow. Existing methods to estimate displacements include block matching and optical flow. Image registration in computer vision seeks reasonable transformations between two images such that one matches the other and has been under-utilized in determining the displacement for BOS image processing. Deformable image registration (DIR) methods allow non-global transformations and are proposed as displacement estimation methods for processing BOS images. Numerical ray tracing simulations are performed to generate synthetic BOS images of various flows. The estimated density gradient results of block matching, optical flow, and DIR methods are compared to the ground truth (the path-averaged density gradient of the schlieren object used in ray tracing) to assess and compare their performances. The performances of these methods are also validated on experimental BOS images to determine the displacement estimation method that is most suitable for high-speed, turbulent flows.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 2","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142995605","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":"Plasma-based anti-/de-icing: an experimental study utilizing supercooled water droplet image velocimetry","authors":"Weiwei Hui,&nbsp;Zhipeng Chen,&nbsp;Jianjun Ma,&nbsp;Xuanshi Meng","doi":"10.1007/s00348-025-03960-y","DOIUrl":"10.1007/s00348-025-03960-y","url":null,"abstract":"<div><p>This paper presents an image velocimetry technique that employs supercooled water droplets as seeding particles in an icing wind tunnel. The innovative work involves reconstructing the pressure distribution using the velocity field measured by the water droplets and providing the water collection efficiency at the leading edge of the airfoil using pathlines. The study compares the relative errors of the velocity fields obtained through traditional particle image velocimetry (PIV) and the supercooled water droplet image velocimetry (SWDIV) methods. Results indicate that the velocity root mean square error of SWDIV is <span>(17.4 %)</span> of the incoming flow velocity, and the average angle error was 5.36°. The streamlines derived from the SWDIV method align well with the water droplet trajectories calculated using the Lagrangian approach, providing a more accurate representation of the flow dynamics involving supercooled water droplets of varying sizes. Using this technique, the study quantitatively analyzes the changing characteristics of the airfoil flow field during the anti-icing and de-icing processes under plasma actuation. Key observations include identifying changes in ice configuration, evaluating water droplet collection efficiency at the leading edge, and analyzing the velocity and pressure fields. In the icing wind tunnel experiments, the incoming flow velocity was 15 <span>(text {m/s})</span>, resulting in a Reynolds number of <span>(1.8 times 10^5)</span>. The liquid water content was 1.0 <span>(text {g/m}^3)</span>, with a median volume diameter of water droplets at 20 <span>(upmu text {m})</span> and an average diameter of 6.4 <span>(upmu text {m})</span> The static temperature of the incoming flow was − 10 °C. The anti-icing research revealed that plasma actuation prevents icing on the leading edge while maintaining the suction peak. However, runback ice formed downstream of the actuator at low incoming flow velocities, significantly reducing local negative pressure and leading to lift loss. Moreover, the aerodynamic effects generated by plasma reduced the peak water droplet collection coefficient at the leading edge by approximately 0.05. When the airfoil’s leading edge was covered with a 5 mm thick layer of mixed ice, its geometric shape became irregular, and the pressure peak was notably diminished. Upon activation of the plasma actuator, the resulting aerodynamic and thermal coupling melted the surface ice, disrupting the adhesion between the ice and the airfoil surface. This caused the ice to detach and be carried downstream by the airflow, effectively achieving de-icing within approximately 203 s. After ice removal, the negative pressure peak on the upper surface of the airfoil’s leading edge returned to baseline levels, restoring lift to a great degree.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 2","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142995618","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":"The effects of wall proximity on the turbulent flow field in a square duct structured with detached divergent ribs on one wall","authors":"Sebastian Ruck,&nbsp;Isaac Lorenzo Mercado","doi":"10.1007/s00348-024-03945-3","DOIUrl":"10.1007/s00348-024-03945-3","url":null,"abstract":"<div><p>The effect of the wall proximity of detached <span>({60,mathrm{ ^{circ }}})</span> divergent ribs applied on one wall in a square duct on the turbulent flow field was investigated. Laser Doppler anemometry (LDA) measurements were conducted for different clearance-to-rib-height ratios in the range of 0.1–1.0 at a Reynolds number (based on the rib height and mean bulk velocity) of 5000. Mean velocities, Reynolds stresses, triple velocity correlations as well as skewness and kurtosis were determined and yield deep insights into the turbulent flow field. The results showed that a geometry-induced secondary fluid motion occurred above and below the rib. The variations in the highly three-dimensional flow field close to the ribs and the geometry-induced secondary flow motion with the clearance-to-rib-height ratio determined the development of the wall-bounded flows and separating shear layers. Large recirculation regions on the bottom duct wall were prevented by the fluid exiting the gap below the detached ribs and separated shear layers pivoted upward in lateral direction. With decreasing wall proximity, lower mean vertical flow velocities above the ribs and the increasing upward fluid flow originating from the flow in the gap attenuated an intense interaction of the separated shear layers with the wall-bounded flow within the inter-rib spacing. Since turbulent structures originated in the shear layers, distributions of high-order statistic moments depend strongly on the shear layer development. Reynolds stresses and triple velocity correlations increased in the direction of the side walls near the rib due to the lateral flow motion, and their peak regions moved away from the wall with increasing clearance-to-rib-height ratios.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 2","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03945-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142995377","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}