Experiments in Fluids最新文献_第7页

Characterizing visual structures in a buoyant plume 浮力羽流中视觉结构的特征

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-08-31 DOI: 10.1007/s00348-024-03862-5

Biman Kalita, Luisa P. Florez, Ella Landau, Riley Ward, James Holyoke, Blair A. Johnson

{"title":"Characterizing visual structures in a buoyant plume","authors":"Biman Kalita, Luisa P. Florez, Ella Landau, Riley Ward, James Holyoke, Blair A. Johnson","doi":"10.1007/s00348-024-03862-5","DOIUrl":"10.1007/s00348-024-03862-5","url":null,"abstract":"<div><p>Turbulent plumes are fascinating to study in large part due to the ability to see the eddies and structures that comprise the exterior structure as they develop in space and time. We perform a laboratory study in which positively buoyant turbulent plumes are generated in a quiescent water tank. Buoyancy is varied by modifying the relative percentages of isopropyl alcohol to water in a mixture placed in a head tank. Photographs captured at steady frame rates record the evolution of the plume as it develops in time and space. A custom algorithm tracks the visible exterior outline of the plume, from which eddies and structures can be identified along the interface between the plume fluid and ambient fluid. Statistical analyses are performed to characterize differences in the distributions of external structures to study their dependence on relative buoyancy between the fluids. Spectral analysis of the edge signal of the plume reveals a <span>(-)</span>2.2 slope, indicative of the range of eddy lengths that comprise turbulent plumes. We explore the relationship between buoyancy with both the plume front velocity and plume spread angle. We find the front velocities to be functions of both the buoyancy and source Reynolds number. However, the spread angles were found to vary only with buoyancy of the plumes, thus proportional to their Richardson numbers.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 9","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142218612","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}

引用次数: 0

Pressure drop measurements over anisotropic porous substrates in channel flow 通道流中各向异性多孔基底上的压降测量

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-08-31 DOI: 10.1007/s00348-024-03873-2

Shilpa Vijay, Mitul Luhar

{"title":"Pressure drop measurements over anisotropic porous substrates in channel flow","authors":"Shilpa Vijay, Mitul Luhar","doi":"10.1007/s00348-024-03873-2","DOIUrl":"10.1007/s00348-024-03873-2","url":null,"abstract":"<p>Previous theoretical and simulation results indicate that anisotropic porous materials have the potential to reduce turbulent skin friction in wall-bounded flows. This study experimentally investigates the influence of anisotropy on the drag response of porous substrates. A family of anisotropic periodic lattices was manufactured using 3D printing. Rod spacing in different directions was varied systematically to achieve different ratios of streamwise, wall-normal, and spanwise bulk permeabilities (<span>(kappa _{xx})</span>, <span>(kappa _{yy})</span>, and <span>(kappa _{zz})</span>). The 3D printed materials were flush-mounted in a benchtop water channel. Pressure drop measurements were taken in the fully developed region of the flow to systematically characterize drag for materials with anisotropy ratios <span>(frac{kappa _{xx}}{kappa _{yy}} in [0.035,28.6])</span>. Results show that all materials lead to an increase in drag compared to the reference smooth wall case over the range of bulk Reynolds numbers tested (<span>(hbox {Re}_b in [500,4000])</span>). However, the relative increase in drag is lower for streamwise-preferential materials. We estimate that the wall-normal permeability for all tested cases exceeded the threshold identified in previous literature (<span>(sqrt{kappa _{yy}}^+> 0.4)</span>) for the emergence of energetic spanwise rollers similar to Kelvin–Helmholtz vortices, which can increase drag. The results also indicate that porous walls exhibit a departure from laminar behavior at different values for bulk Reynolds numbers depending on the geometry.</p>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 9","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03873-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142218610","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}

引用次数: 0

Simultaneous measurement of the distributed longitudinal strain and velocity field for a cantilevered cylinder exposed to turbulent cross flow 同时测量暴露在湍流交叉流中的悬臂圆柱体的分布式纵向应变和速度场

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-08-31 DOI: 10.1007/s00348-024-03870-5

Francisco J. G. de Oliveira, Zahra Sharif Khodaei, Oliver R. H. Buxton

{"title":"Simultaneous measurement of the distributed longitudinal strain and velocity field for a cantilevered cylinder exposed to turbulent cross flow","authors":"Francisco J. G. de Oliveira, Zahra Sharif Khodaei, Oliver R. H. Buxton","doi":"10.1007/s00348-024-03870-5","DOIUrl":"10.1007/s00348-024-03870-5","url":null,"abstract":"<div><p>The structural response of a cantilevered cylinder under free-stream conditions both with low and high turbulence intensity generated by turbulence-generating grids is analysed with concurrent measurements of the velocity field and the distributed strain. The thin-walled cylinder, with a diameter (<i>D</i>) of 50 mm, is mounted in a water flume as a cantilevered beam supported at one end, with 95% of its body submerged and exposed to cross flow yielding a Reynolds number of Re = 25000. We employ a novel combination of simultaneous particle image velocimetry and distributed strain measurements using Rayleigh backscattering fibre optic sensors. These sensors are embedded onto the surface of the cylinder to measure the experienced strain (<span>(varepsilon )</span>) of the structure along its spanwise direction, covering both the windward and leeward faces of the cylinder. The sensors fine spatial resolution allows us to discern the influence of the flow on the structural response of the cylinder in two distinct regions of the structure: upstream and downstream of the mean separation location. This differentiation allows us to isolate the local effects introduced by the free-stream conditions on the loading events over the body from the global force generated by the vortex shedding and other coherent motions present within the flow. Distinguishing between these direct and indirect effects helps determine which is more relevant for fatigue-life cycle analysis. The cross power spectral density between the fluctuating velocity field and the strain reveals that the load is dominated by the vortex shedding, and this relationship is intensified with the introduction of free-stream turbulence. It also helps to discern the different dynamics imposed by the two free-stream turbulence conditions.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 9","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03870-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142218798","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}

引用次数: 0

The influence of water turbulence on surface deformations and the gas transfer rate across an air–water interface 水湍流对空气-水界面表面变形和气体传输速率的影响。

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-08-28 DOI: 10.1007/s00348-024-03864-3

Pim A. Bullee, Stefan Weichert, Astri Nore, Leon Li, Simen Å. Ellingsen, R. Jason Hearst

{"title":"The influence of water turbulence on surface deformations and the gas transfer rate across an air–water interface","authors":"Pim A. Bullee, Stefan Weichert, Astri Nore, Leon Li, Simen Å. Ellingsen, R. Jason Hearst","doi":"10.1007/s00348-024-03864-3","DOIUrl":"10.1007/s00348-024-03864-3","url":null,"abstract":"<div><p>We present experimental results of a study on oxygen transfer rates in a water channel facility with varying turbulence inflow conditions set by an active grid. We compare the change in gas transfer rate with different turbulence characteristics of the flow set by four different water channel and grid configurations. It was found that the change in gas transfer rate correlates best with the turbulence intensity in the vertical direction. The most turbulent cases increased the gas transfer rate by 30% compared to the low turbulence reference case. Between the two most turbulent cases studied here, the streamwise turbulence and largest length scales in the flow change, while the gas transfer rate is relatively unchanged. In contrast, for the two less turbulent cases where the magnitude of the fluctuations normal to the free surface are also smaller, the gas transfer rate is significantly reduced. Since the air–water interface plays an important role in the gas transfer process, special attention is given to the free-surface deformations. Despite taking measures to minimise it, the active grid also leaves a direct imprint on the free surface, and the majority of the waves on the surface originate from the grid itself. Surface deformations were, however, ruled out as a main driver for the increase in gas transfer because the increase in surface area is < 0.25%, which is two orders of magnitude smaller than the measured change in the gas transfer rate.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 9","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11358190/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142103176","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}

引用次数: 0

A micro-hot-wire anemometry probe with elongated stubs for turbulent boundary layer measurements 用于湍流边界层测量的带细长桩的微型热线风速探头

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-08-28 DOI: 10.1007/s00348-024-03871-4

Baptiste Baradel, Alain Giani, Fabien Méry, Philippe Combette, Olivier Léon

引用次数: 0

Resolving high-frequency aeroacoustic noises of high-speed dual-impinging jets using fast pressure-sensitive paint 利用快速压敏涂料解决高速双顶压喷气机的高频气声噪声问题

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-08-26 DOI: 10.1007/s00348-024-03875-0

Chunhua Wei, Haoyuan Zhang, Hongling Fan, Peng Wang, Di Peng, Yingzheng Liu

{"title":"Resolving high-frequency aeroacoustic noises of high-speed dual-impinging jets using fast pressure-sensitive paint","authors":"Chunhua Wei, Haoyuan Zhang, Hongling Fan, Peng Wang, Di Peng, Yingzheng Liu","doi":"10.1007/s00348-024-03875-0","DOIUrl":"10.1007/s00348-024-03875-0","url":null,"abstract":"<div><p>This study experimentally determines high-frequency aeroacoustic noises of the high-speed dual-impinging jet, focusing on the generation and evolution mechanism between impingement tones modes and far-field acoustic spectra. The variables of the high-speed impinging jet are Mach number (Ma = 0.9 and 1.1), fixed diameter (D) of nozzle, nozzle spacing (3.5D), and impingement distance (4D). A novel fast-responding pressure-sensitive paint (fast-PSP) with a significantly extended frequency response ability was designed to develop an accurate phase-resolving propagation process of aeroacoustic noises and handle high impingement momentum challenges posed by the high-speed impinging jet. The PSP raw data were enhanced by calibration, image restoration, and proper orthogonal decomposition filtering. Two distinct far-field spectral characteristics were identified based on synchronized acoustic measurements. The existence of the stagnation region affected by the fountain effect in the dual-impinging jet was determined using spatial–temporal cross-correlation analysis. Subsequently, the concurrent axisymmetric dual annulus mode and its coupling behavior at Ma = 0.9 and the non-axisymmetric helical mode and its periodic fragmentation-reconstruction patterns at Ma = 1.1 were identified by spectral proper orthogonal decomposition. Finally, the spatial–temporal evolution of the phase-locked first-order mode was extracted, and the transient variations of coherent structures and their mechanisms for discrete tone noise generation were quantitatively investigated. The expansion and coupling of the dual annulus modes promoted the dominance of single-tone peaks across the entire acoustic spectrum. The helical mode, exhibiting both rotational and expansion behaviors, enhanced the coherent vorticity at the periphery of the coherent structures, resulting in intense impingement tones sound sources.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 9","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227394","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}

引用次数: 0

Particle streak velocimetry: a review 粒子条纹测速：综述

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-08-20 DOI: 10.1007/s00348-024-03857-2

Dapeng Zhang, Cameron Tropea, Wu Zhou, Tianyi Cai, Haoqin Huang, Xiangrui Dong, Limin Gao, Xiaoshu Cai

{"title":"Particle streak velocimetry: a review","authors":"Dapeng Zhang, Cameron Tropea, Wu Zhou, Tianyi Cai, Haoqin Huang, Xiangrui Dong, Limin Gao, Xiaoshu Cai","doi":"10.1007/s00348-024-03857-2","DOIUrl":"10.1007/s00348-024-03857-2","url":null,"abstract":"<div><p>Particle streak velocimetry (PSV) is a Lagrangian velocity measurement method based on streak imaging of moving particles and is regarded as the origin of particle image velocimetry (PIV) and particle tracking velocimetry (PTV). Recently, the PSV technique has undergone further developments, realizing measurements of three velocity components in three dimensions (3D3C), by combining with stereoscopic observation, defocused imaging, light field photography and /or holography. Moreover, image processing algorithms based on deep learning have been successfully applied to PSV. Compared with PIV and PTV, the PSV technique can exhibit several advantages, including extending the upper limit of the velocity measurement range under the same equipment conditions, measuring with lower illumination intensity, often an overall lower equipment complexity and cost for the same measuring requirement, as well as avoiding the particle matching problems of PTV. However, the PSV method also has obstacles to overcome, such as directional ambiguity and the difficulty in identifying streak crossings. For the directional ambiguity problem, there are currently time-coding, color-coding, brightness-coding and determination methods using additional image frames that can be employed. The main application areas of PSV currently include microfluidics, high-velocity flows and large-scale flow field measurements. This review presents the state of the art of PSV and summarizes advantages, disadvantages, accuracy, complexity and application of various configurations. The configurations discussed are focused on those measuring three velocity components and several examples are described in which PSV can be advantageously applied. The review concludes with some future developments that can be anticipated.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 9","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142218682","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}

引用次数: 0

Two-dye two-color laser-induced fluorescence spectroscopy on droplets of green solvent water/ethanol mixtures for thermometry and mixture composition 在绿色溶剂水/乙醇混合物液滴上进行双染双色激光诱导荧光光谱分析，以测定温度和混合物成分

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-08-20 DOI: 10.1007/s00348-024-03868-z

Hannah Ulrich, Richard Weiß, Lars Zigan

引用次数: 0

Impact dynamics of droplets on convex structures: an experimental study with a maximum spreading diameter model for convex surface impacts 凸面结构上液滴的撞击动力学：利用凸面撞击的最大扩散直径模型进行的实验研究

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-08-19 DOI: 10.1007/s00348-024-03865-2

Nuri Erdem Ersoy, Fenghao Shi, David L. S. Hung

{"title":"Impact dynamics of droplets on convex structures: an experimental study with a maximum spreading diameter model for convex surface impacts","authors":"Nuri Erdem Ersoy, Fenghao Shi, David L. S. Hung","doi":"10.1007/s00348-024-03865-2","DOIUrl":"10.1007/s00348-024-03865-2","url":null,"abstract":"<div><p>Droplet impact is a common phenomenon in daily life and various industrial applications. Previous research shows that surface geometry significantly influences impact outcomes. However, there is a gap in systematic research on how convex structures, similar in size to the droplet, influence impact behaviors. To address this, our study focused on producing various targets with different convexity to investigate the morphological evolution of droplet impact. Using high-speed imaging techniques, we examined these impacts with Weber numbers ranging from 5 to 346. The experimental results show that dry convex surfaces increase the maximum spreading diameter of droplets by altering liquid mass redistribution. Reduced air entrapment diminishes the circumferential instability of deformed droplets on these surfaces, as evidenced by fewer fingers formed. This study also proposes a hybrid model to predict the maximum spreading diameter on convex surfaces using the energy conservation method. Benefiting from models for flat surfaces, this new approach accounts for convex surface impacts, which alter the impact characteristics according to the convexity of the impact geometry. The model assumes that the droplet at its maximum spreading diameter resembles either a disc or a rim. Notably, the rim assumption was quite evident in several convex surface impacts, presenting a donut-shaped expansion. These results are combined through weighted summation The hybrid model’s predictions show a superior agreement with the experimental data compared to existing models. Additionally, the model’s weighting factors provide insights into the distribution of liquid mass between the central film and the surrounding rim.</p><h3>Graphical abstract</h3><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 8","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142218786","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}

引用次数: 0

A multi-directional redundant 3D-LPT system for ship–flight–deck wind interactions 用于船-飞行-甲板风相互作用的多方向冗余 3D-LPT 系统

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-08-17 DOI: 10.1007/s00348-024-03867-0

Ilda Hysa, Marthijn Tuinstra, Andrea Sciacchitano, Fulvio Scarano, Mark-Jan van der Meulen, Thomas Rockstroh, Eric W. M. Roosenboom

{"title":"A multi-directional redundant 3D-LPT system for ship–flight–deck wind interactions","authors":"Ilda Hysa, Marthijn Tuinstra, Andrea Sciacchitano, Fulvio Scarano, Mark-Jan van der Meulen, Thomas Rockstroh, Eric W. M. Roosenboom","doi":"10.1007/s00348-024-03867-0","DOIUrl":"10.1007/s00348-024-03867-0","url":null,"abstract":"<div><p>In the past years, volumetric velocimetry measurements with helium-filled soap bubbles as tracer particles have been introduced in wind tunnel experiments and performed at large-scale, enabling the study of complex body aerodynamics. A limiting factor is identified in the field of wind engineering, where the flow around ships is frequently investigated. Considering multiple wind directions, the optical access for illumination and 3D imaging rapidly erodes the measurement regions due to shadows and incomplete triangulation. This work formalizes the concepts of volumetric losses and camera redundancy, and examines the performance of multi-directional illumination and imaging for monolithic and partitioned modes. The work is corroborated by experiments around a representative ship model. The study shows that a redundant system of cameras yields the largest measurement volume when partitioned into subsystems. The 3D measurements employing two illumination directions and seven cameras, yield the time-averaged velocity field around the ship. Regions of flow separation and recirculation are revealed, as well as sets of counter-rotating vortices in several stations from the ship bow to the flight–deck. The unsteady regime at the flight–deck is examined by proper orthogonal decomposition, indicating that the technique is suited for the analysis of large-scale unsteady flow features.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 8","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03867-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227367","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}

引用次数: 0