Experiments in Fluids最新文献_第3页

Conditional statistics at the turbulent/non-turbulent interface of variable viscosity jets 可变粘度喷流湍流/非湍流界面的条件统计数据

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-11-13 DOI: 10.1007/s00348-024-03915-9

Léa Voivenel, Emilien Varea, Gilles Godard, Luminita Danaila

{"title":"Conditional statistics at the turbulent/non-turbulent interface of variable viscosity jets","authors":"Léa Voivenel, Emilien Varea, Gilles Godard, Luminita Danaila","doi":"10.1007/s00348-024-03915-9","DOIUrl":"10.1007/s00348-024-03915-9","url":null,"abstract":"<div><p>In nature as well as in industrial applications, turbulent mixing is ubiquitous. In most cases, these are different fluids with different physical properties (density and/or viscosity). Moreover, all important changes such as mass, momentum and scalar fluxes occur across the turbulent/non-turbulent interface, a thin and sharp layer that separates the turbulent core from the irrotational surrounding fluid. In this paper, we present statistics conditioned on the instantaneous interface position in the very near field of a variable viscosity jet to study the birth and growth of turbulence. The simultaneous scalar concentration and velocity fields are obtained from planar laser-induced fluorescence, where the images undergo an original correction and normalization process, and stereo-particle image velocimetry, respectively. We show that the turbulence is much more advanced in the variable viscosity flow (VVF), which exhibits some features that are visible much later in the constant viscosity flow (CVF). Furthermore, this study reveals a change in the nature of the mixing process between VVF and CVF, which needs to be further investigated.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 12","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142636894","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

Viscous and turbulent stress measurements above and below laboratory wind waves 实验室风浪上方和下方的粘应力和湍流应力测量结果

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-11-13 DOI: 10.1007/s00348-024-03898-7

Janina Tenhaus, Marc P. Buckley, Silvia Matt, Ivan B. Savelyev

{"title":"Viscous and turbulent stress measurements above and below laboratory wind waves","authors":"Janina Tenhaus, Marc P. Buckley, Silvia Matt, Ivan B. Savelyev","doi":"10.1007/s00348-024-03898-7","DOIUrl":"10.1007/s00348-024-03898-7","url":null,"abstract":"<p>The influence of wind stress, wind drift, and wind-wave (microscale) breaking on the coupled air–sea boundary layer is poorly understood. We performed high-resolution planar and stereo velocity measurements within the first micrometers to centimeters above and below surface gravity waves at the University of Miami’s SUSTAIN air–sea interaction facility. A particle image velocimetry (PIV) system was adapted and installed in the large (18 m long, 6 m wide) wind-wave tunnel at a fetch of approximately 10 m. In addition, wave field properties were captured by laser-induced fluorescence (LIF). Experiments were conducted with wind waves and wind over mechanically generated swell. In this work, we focus on rather smooth, young, wind-generated waves. We present instantaneous velocity and vorticity fields above and below the air–water interface for the same wind-wave conditions. Both instantaneous and phase-averaged fields show strong along-wave modulations in viscous stress. For steeper waves, we observe airflow separation and increased negative turbulent stress below crests, accompanied by sporadic drops in viscous stress below zero. We describe the wave-induced modulations of the airflow structure as well as the wind-induced water dynamics and discuss the importance of the viscous stress for the total momentum budget.</p>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 12","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03898-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142636895","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

Flow sensors for on-chip microfluidics: promise and challenges 用于片上微流体的流量传感器：前景与挑战

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-11-12 DOI: 10.1007/s00348-024-03918-6

Harsh Deswal, Shivji Prasad Yadav, Shiv G. Singh, Amit Agrawal

引用次数: 0

Measuring acoustic velocity map in turbulent flow using sub-Nyquist-rate PIV system 利用次奈奎斯特速率 PIV 系统测量湍流中的声速图

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-11-12 DOI: 10.1007/s00348-024-03913-x

Simon Rampnoux, Islam Ramadan, Solène Moreau, Mabrouk Ben Tahar

{"title":"Measuring acoustic velocity map in turbulent flow using sub-Nyquist-rate PIV system","authors":"Simon Rampnoux, Islam Ramadan, Solène Moreau, Mabrouk Ben Tahar","doi":"10.1007/s00348-024-03913-x","DOIUrl":"10.1007/s00348-024-03913-x","url":null,"abstract":"<p>The present study provides an experimental method for measuring acoustic velocity components (amplitude and spatial phase shift) in the presence of turbulent flows using either low-frequency particle image velocimetry (PIV) or laser Doppler velocimetry (LDV). The approach leverages compressed sensing (CS) principles to overcome the limitations of classical PIV techniques, such as the need for a reference signal for synchronization, large data size and long measurement duration. Theoretical aspects of CS for extracting acoustic components from PIV and LDV measurements are discussed. The proposed method is applied to both PIV and LDV systems, and the results are compared with microphone measurements. The results show the ability of the proposed experimental method to accurately measure acoustic velocity components at different frequencies and sound pressure levels in the presence of turbulent flow. The presented experimental method offers several advantages, including reduced data size, no need for phase-locking measurements and reduced measurement duration. The actual limitation is the need for a low noise-to-signal ratio (NSR). The effects of high NSR can be mitigated by increasing acquisition time in some cases. The non-intrusive nature of the method makes it valuable for aeroacoustic research. Ongoing research focuses on applying the method to higher-order duct modes and investigating its potential for modal decomposition using optical techniques.</p>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 12","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142600608","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

Fluid wetting and penetration characteristics in T-shaped microchannels T 型微通道中的流体润湿和渗透特性

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-11-09 DOI: 10.1007/s00348-024-03906-w

Huijie Zhang, Anja Lippert, Ronny Leonhardt, Tobias Tolle, Luise Nagel, Tomislav Marić

{"title":"Fluid wetting and penetration characteristics in T-shaped microchannels","authors":"Huijie Zhang, Anja Lippert, Ronny Leonhardt, Tobias Tolle, Luise Nagel, Tomislav Marić","doi":"10.1007/s00348-024-03906-w","DOIUrl":"10.1007/s00348-024-03906-w","url":null,"abstract":"<div><p>A thorough understanding of media tightness in automotive electronics is crucial for ensuring more reliable and compact product designs, ultimately improving product quality. Concerning the fundamental characteristics of fluid leakage issues, the dynamic wetting and penetration behavior on small scales is of special interest and importance. In this work, four T-shaped microchannels with one inlet and two outlets are experimentally investigated in terms of contact angle dynamics and interface movement over time, generating novel insight into the wetting mechanisms and fluid distribution. With a main channel width of 1 mm, a crevice width of <span>(w = {0.3},hbox {mm}, {0.4},hbox {mm})</span> and a rounding edge radius of <span>(r = {0.1},hbox {mm}, {0.2},hbox {mm})</span>, the geometrical effects on the fluid penetration depth in the crevice and the interface edge pinning effect are analyzed quantitatively using an automated image processing procedure. It is found that the measured dynamic contact angles in all parts can be well described by molecular kinetic theory using local contact line velocities, even with local surface effects and abrupt geometry changes. Moreover, a smaller crevice width, a sharper edge and a larger flow velocity tend to enhance the interface pinning effect and prevent fluid penetration into the crevice. The rounding radius has a more significant effect on the interface pinning compared with crevice width. The experimental data and image processing algorithm are made publicly available.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 11","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03906-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142596017","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

Phase changes in burning precursor-laden single droplets leading to puffing and micro-explosion 燃烧前体单液滴中的相变导致膨化和微爆炸

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-11-07 DOI: 10.1007/s00348-024-03895-w

Benjamin A. Südholt, Arne Witte, Greg J. Smallwood, Sebastian A. Kaiser, Lutz Mädler, Niklas Jüngst

{"title":"Phase changes in burning precursor-laden single droplets leading to puffing and micro-explosion","authors":"Benjamin A. Südholt, Arne Witte, Greg J. Smallwood, Sebastian A. Kaiser, Lutz Mädler, Niklas Jüngst","doi":"10.1007/s00348-024-03895-w","DOIUrl":"10.1007/s00348-024-03895-w","url":null,"abstract":"<div><p>When producing metal-oxide nanoparticles via flame spray pyrolysis, precursor-laden droplets are ignited and undergo thermally induced disintegration, called ‘puffing’ and ‘micro-explosion’. In a manner that is not fully understood, these processes are associated with the formation of dispersed phases inside the droplets. This work aims at visualizing the interior of precursor-laden burning single droplets via diffuse back illumination and microscopic high-speed imaging. Solutions containing iron(III) nitrate nonahydrate (INN) and tin(II) 2-ethylhexanoate (Sn-EH) were dispersed into single droplets of sub-100 μm diameter that were ignited by passing through a heated coil. At low precursor concentration, 50% of the INN-laden droplets indicate a gas bubble of about 5 μm diameter in the center of the droplet. The bubble persists for several hundred microseconds at a similar size. In almost all of these cases, the bubble expands at some point and the droplet ends up in a micro-explosion. In some of these instances, the droplet’s surface shows spatial brightness modulations, i.e., surface undulations, indicating the formation of a viscous shell. With increasing INN concentration, the fraction of droplets showing surface undulations, gas bubbles, and micro-explosions drastically decreases. This may be associated with a more rigid viscous shell and reduced mobility of bubbles. Bright incandescent streaks originating from the disrupting INN-laden droplets, may indicate sub-micrometer droplets or particles from within the droplets or formed in the gas phase. In contrast, Sn-EH-laden droplets show very fast disruptions, typically less than 10 μs from first visible deformation to ejection of secondary droplets. Bubbles and surface undulations were not observed.</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 11","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03895-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142595503","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

Dam break flow through rigid-emergent vegetation 大坝断流穿过刚性植被

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-11-06 DOI: 10.1007/s00348-024-03901-1

Adel A. Mahmoud, Tatsuhiko Uchida

{"title":"Dam break flow through rigid-emergent vegetation","authors":"Adel A. Mahmoud, Tatsuhiko Uchida","doi":"10.1007/s00348-024-03901-1","DOIUrl":"10.1007/s00348-024-03901-1","url":null,"abstract":"<p>Dam failures pose a significant threat to life and property. This study investigates the potential of rigid emergent vegetation to attenuate dam break waves, reducing their destructive impact. Experiments explored the effect of varying vegetation field lengths on wave propagation. Wooden cylinders with consistent diameter (1.0 cm) and density (0.067) simulated the rigid vegetation in a straight, flat rectangular channel. Four different vegetation lengths and three bore conditions for different reservoir and tailwater depths were examined to analyze their influence on dam break wave behavior. The results demonstrate the effectiveness of vegetation in dissipating wave energy, leading to a rapid decrease in wave height and celerity. Interestingly, increasing vegetation length significantly attenuates the wave height downstream of the vegetation zone, while having no significant impact on the reflection wave height upstream of the vegetation. This finding highlights the targeted effectiveness of strategically placed vegetation in shielding downstream areas. The study also clarifies that celerity can be calculated using shallow water equations for both upstream and downstream regions with wave height and tailwater depth. However, within the vegetation, drag forces significantly reduce celerity. A novel equation, derived from wavefront profiles, was proposed and validated to accurately calculate celerity within the vegetation field. These findings provide valuable data for validating numerical models simulating dam break wave interactions with vegetation.</p>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 11","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03901-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142595613","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

Cylinder wake flow in confined channel and its active control by sweeping jets 封闭水道中的圆筒形尾流及其通过扫掠射流的主动控制

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-11-05 DOI: 10.1007/s00348-024-03910-0

Jinsheng Song, Zihao Qiu, Yingzheng Liu, Xin Wen

{"title":"Cylinder wake flow in confined channel and its active control by sweeping jets","authors":"Jinsheng Song, Zihao Qiu, Yingzheng Liu, Xin Wen","doi":"10.1007/s00348-024-03910-0","DOIUrl":"10.1007/s00348-024-03910-0","url":null,"abstract":"<div><p>The wake dynamics of the flow past a confined circular cylinder and its active control by sweeping jets (SWJs) and steady jets (SJs) positioned at the front stagnation points were experimentally investigated using particle image velocimetry and pressure measurements. Experiments were conducted across a range of Reynolds numbers (Re, based on the incoming flow velocity and the cylinder diameter) from 10,000 to 45,000 and blockage ratios (<span>(beta)</span>) of <span>(1/2)</span>, <span>(1/3)</span>, <span>(1/4)</span>, and <span>(1/5)</span>. A comprehensive comparison between the current results and existing literature on natural flow dynamics fills the knowledge gap and reveals that confinement gradually reduces the time-average pressure coefficient (<span>(C_{{text{p}}})</span>) and increases the drag coefficient (<span>(C_{{text{D}}})</span>) and Strouhal number (St). The interaction between the wake and lateral wall shear layer gradually increased as <span>(beta)</span> increased. Both SWJs and SJs effectively suppressed wake fluctuations, and the statistical characteristics of the flow field and proper orthogonal decomposition analysis indicated a consistent flow control mechanism between the two methods. However, the SJs introduced external fluctuations and unbalanced forces in the forward flow field, resulting in a wake flow asymmetry. By contrast, SWJs provide more uniform control and superior flow control effectiveness and efficiency.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 11","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142579530","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 speckle projection-based 3D digital image correlation method for measuring dynamic liquid surfaces 基于斑点投影的三维数字图像相关方法，用于测量动态液体表面

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-11-05 DOI: 10.1007/s00348-024-03907-9

Kai Wang, Bin Cheng, Derui Li, Sheng Xiang

{"title":"A speckle projection-based 3D digital image correlation method for measuring dynamic liquid surfaces","authors":"Kai Wang, Bin Cheng, Derui Li, Sheng Xiang","doi":"10.1007/s00348-024-03907-9","DOIUrl":"10.1007/s00348-024-03907-9","url":null,"abstract":"<div><p>Measuring dynamic liquid surfaces is a significant challenge in fluid mechanics and sloshing dynamics, with a notable lack of high-precision, effective full-field measurement methods. To resolve this challenge, this research proposes a speckle projection-based 3D digital image correlation (3D-DIC) method for the measurement of dynamic liquid surfaces. The approach employs liquid staining and speckle projecting to create textured patterns on the liquid surface, which are then captured by binocular cameras. The binocular cameras are calibrated using a ratio-invariant method to accurately obtain the internal and external parameter matrices. Subsequently, algorithm based on zero-mean normalized cross-correlation (ZNCC) is utilized to reconstruct the dynamic liquid surface wave height field. To validate the accuracy of the method, a geometric optical numerical model is established to simulate binocular images of regular wave liquid surfaces with projected speckle patterns. The results show that full-field root mean square (RMS) error in simulated liquid surface measurement is less than 0.019 mm. Physical experiments were further conducted to confirm the method's applicability, achieving a maximal measurement error of 0.133 mm for real dynamic liquid surfaces. Results demonstrate that the proposed method achieves high-precision, non-contact, and full-field measurements of dynamic liquid surfaces, making it ideal for laboratory measurements of flowing liquids.</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":"65 11","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142587776","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

Flow characteristics of a Francis turbine under deep part-load and various no-load conditions 混流式水轮机在深度部分负荷和各种空载条件下的流量特性

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-11-04 DOI: 10.1007/s00348-024-03904-y

Araz Rezavand Hesari, Maxime Gauthier, Maxime Coulaud, Yvan Maciel, Sébastien Houde

{"title":"Flow characteristics of a Francis turbine under deep part-load and various no-load conditions","authors":"Araz Rezavand Hesari, Maxime Gauthier, Maxime Coulaud, Yvan Maciel, Sébastien Houde","doi":"10.1007/s00348-024-03904-y","DOIUrl":"10.1007/s00348-024-03904-y","url":null,"abstract":"<div><p>In the recent years, increased use of hydraulic turbines in off-design operating conditions such as no-load and deep part-load has resulted in increased damage to the turbines. A detailed understanding of the fluctuating flow phenomena can help to identify and mitigate the potentially damaging flow structures. This paper presents a comprehensive experimental and numerical study of the flow phenomena at the inlet of a Francis turbine at four no-load operating conditions, including speed-no-load and a deep part-load operating condition. Measurements are taken using a high-frequency stereoscopic endoscopic particle image velocimetry method on radial–azimuthal planes, covering the vaneless space and a large part of the interblade channels at different spans. For the speed-no-load condition, experimental data are enriched with unsteady RANS simulation data to understand the three-dimensional behavior of the flow. The average flow phenomena, transient structures and velocity fluctuations are discussed and compared among different operating points. At all operating points, the strongest average flow circulation zone (strong enough to form a vortex only at one operating condition) consistently exhibits the highest velocity fluctuation energy. The results show that the highest velocity fluctuations, and thus the most energetic dynamic structures, are in a no-load operating point with a guide vane opening smaller than speed-no-load. Position and intensity of the interblade vortices varies not only with the guide vane opening but also with the amount of torque extracted by the runner.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 11","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142579514","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