Experiments in Fluids最新文献

Wall pressure control of a 3D cavity with lateral apertures and wall proximity 具有横向开孔和接近壁面的三维空腔的壁面压力控制

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-11-15 DOI: 10.1007/s00348-024-03900-2

Tarek Ammam, Laurent Keirsbulck, Jérémy Basley, Etienne Grappein, Sebastien Delprat, Tewfik Benazzouz, Denis Cornu, Marc Lippert, David Boussemart

{"title":"Wall pressure control of a 3D cavity with lateral apertures and wall proximity","authors":"Tarek Ammam, Laurent Keirsbulck, Jérémy Basley, Etienne Grappein, Sebastien Delprat, Tewfik Benazzouz, Denis Cornu, Marc Lippert, David Boussemart","doi":"10.1007/s00348-024-03900-2","DOIUrl":"10.1007/s00348-024-03900-2","url":null,"abstract":"<div><p>Flows over cavities are relevant to many branches of engineering and are known to be a source of instabilities, high-pressure disturbances, and large recirculating regions, leading to excessive pressure loads. In this paper, we study the dynamical behavior of a 6.44:1 length-to-depth transitional cavity flow (i.e., where the shear layer partly enters the cavity) with wall proximity and lateral apertures. Mitigation of pressure loads is investigated through steady blowing upstream of the cavity’s leading edge. Concurrent pressure and particle image velocimetry (PIV) measurements along with companion unsteady numerical simulations have been performed to identify the mechanisms underlying the flow dynamics of both baseline and controlled cases. Experiments are reproduced numerically using the Improved Delayed Detached Eddy Simulations (<span>IDDES</span>) approach with shear stress transport eddy viscosity model (<span>(k-omega)</span> SST) at a Reynolds number of <span>(Re=2.8 times 10^5)</span>. Results underline that steady blowing changes the flow drastically upstream of the cavity by thickening the boundary layer and reducing the flow rate passing the cavity. The controlled flow transforms the dynamics of the cavity shear layer, impacting the inner cavity flow, and leads to a significant reduction of the pressure loads. This mitigation is associated with a strong reduction in turbulent momentum at the shear layers interface.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 12","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142636772","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

Multiscale analysis of the textural atomization process of a rocket engine-assisted coaxial jet 火箭发动机辅助同轴射流纹理雾化过程的多尺度分析

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-11-14 DOI: 10.1007/s00348-024-03916-8

Leonardo Geiger, Nicolas Fdida, Christophe Dumouchel, Jean-Bernard Blaisot, Luc-Henry Dorey, Marie Théron

{"title":"Multiscale analysis of the textural atomization process of a rocket engine-assisted coaxial jet","authors":"Leonardo Geiger, Nicolas Fdida, Christophe Dumouchel, Jean-Bernard Blaisot, Luc-Henry Dorey, Marie Théron","doi":"10.1007/s00348-024-03916-8","DOIUrl":"10.1007/s00348-024-03916-8","url":null,"abstract":"<div><p>A method for analyzing liquid ligaments of a textural atomization process is presented in this article for the case of a rocket engine type-assisted atomization process under combustion. The operating point positions the atomization process in the fiber-type regime carrying an intense textural atomization process. Multiscale in nature, the method based on image analysis associates a scale distribution with a family of ligaments, this distribution being sensitive to the number, size and shape of these ligaments. The quality of scale distributions measured by image analysis depends on the spatial resolution and the precision of area measurements of surfaces with curved boundaries but described by square pixels. Part of the work consisted of improving the method for measuring scale distributions by using a sub-pixel image analysis technique and refining the surface area measurement method. Another part directed the multiscale analysis toward the estimation of the diameter distributions of the blobs that characterize the large-scale deformation of the ligaments<b>.</b> The analysis describes the atomization process at a level of detail never reached. For instance, assuming that the blobs are drops in formation, the estimated diameter distribution (bimodal in the case examined here) and the number of these drops are evaluated as a function of the distance from the injector. This information indicates where the process is most intense and where it stops. Furthermore, these diameter distributions receive a mathematical expression whose parameters report clear evolutions with the distance from the injector. This shows the possibility of elaborating mathematical models appropriate for textural atomization mechanisms.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 12","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142636725","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

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

Air cavity deformation by single jointed diver model entry bodies 单关节潜水员模型进入体的气腔变形

IF 2.4 3区工程技术

Experiments in Fluids Pub Date : 2023-10-13 DOI: 10.1007/s00348-023-03712-w

Elizabeth Gregorio, Elias Balaras, Megan C. Leftwich

{"title":"Air cavity deformation by single jointed diver model entry bodies","authors":"Elizabeth Gregorio, Elias Balaras, Megan C. Leftwich","doi":"10.1007/s00348-023-03712-w","DOIUrl":"10.1007/s00348-023-03712-w","url":null,"abstract":"<div><p>Competitive divers are able to attain much higher scores when they perform a splash-less entry. To achieve this goal, they use the “rip” entry maneuver where they roll their body forward immediately after impact. This dynamic shape change after impact separates them from previously studied entry bodies. An experimental study of a geometrically simplified hinged diver model is presented. The results for five different hinged models are reported. Geometric and hinge stiffness changes are used to identify the most important aspects of the maneuver. The trajectory of these models after impact and the estimated size of the entrained air cavity are reported. The models that deform the fastest also have the largest final estimated air cavity. A non-dimensional time based on the time to complete deformation is found to collapse the estimated size of the air cavity for all models that deform before the trailing air cavity collapses. Fixed models are introduced to compare the hinged models to non-deforming entry bodies. The hinged models are found to have between 42% and 154% larger estimated air cavities during the final measurement than their fixed counterpart. At the moment of deep seal, two distinct air cavities are formed: one that connects to the atmosphere above the pool that has smooth walls and a lower cavity largely composed of small bubbles. This composition is analogous to observations of competitive divers. Entry bodies that deform are found to significantly change the shape and formation of the air cavity.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"64 11","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41228860","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

Assessment of aerodynamic roughness parameters of turbulent boundary layers over barnacle-covered surfaces 藤壶覆盖表面湍流边界层空气动力学粗糙度参数的评估

IF 2.4 3区工程技术

Experiments in Fluids Pub Date : 2023-10-13 DOI: 10.1007/s00348-023-03709-5

Takfarinas Medjnoun, Manuel Aguiar Ferreira, Ralf Reinartz, Bagus Nugroho, Jason Monty, Nicholas Hutchins, Bharathram Ganapathisubramani

{"title":"Assessment of aerodynamic roughness parameters of turbulent boundary layers over barnacle-covered surfaces","authors":"Takfarinas Medjnoun, Manuel Aguiar Ferreira, Ralf Reinartz, Bagus Nugroho, Jason Monty, Nicholas Hutchins, Bharathram Ganapathisubramani","doi":"10.1007/s00348-023-03709-5","DOIUrl":"10.1007/s00348-023-03709-5","url":null,"abstract":"<div><p>Full-scale drag penalty predictions of flows over rough walls require surface roughness characterisation from laboratory experiments or numerical simulations. In either approach, it is necessary to determine the so-called equivalent sand-grain roughness height (<span>(k_s)</span>). There are several steps involved in determining this aerodynamic roughness lengthscale, but its procedure typically includes a combination of measurement of wall-shear stress (<span>(tau _w)</span>) using direct or indirect methods as well as analysis of velocity profiles. Indirect methods usually rely on assumptions made about flow and its scaling including the validity of universal outer-layer similarity. However, the implications of the underlying assumptions involved in full-scale drag prediction are unclear. In this work, we carry out wind tunnel measurements over a realistic rough surface (from a fouled ship-hull) to evaluate the impact of different methods with an emphasis on using the outer-layer similarity hypothesis for full-scale drag predictions. Wall-shear stress is measured using an in-house floating-element drag balance (DB), and velocity profiles are obtained using particle image velocimetry (PIV), allowing the evaluation of <span>(k_s)</span>, and the associated wake parameters through several methods. The aerodynamic roughness parameters hence obtained are used for full-scale drag penalty calculations. It is observed that the predicted drag penalty can vary by over 15<span>(%)</span> among the different methods highlighting the care that should be taken when employing such methods.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"64 11","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-023-03709-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41228870","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

Turbulent flow and friction in a pipe with repeated rectangular ribs 具有重复矩形肋的管道中的湍流和摩擦

IF 2.4 3区工程技术

Experiments in Fluids Pub Date : 2023-09-23 DOI: 10.1007/s00348-023-03685-w

M. J. Tummers, M. C. Schenker-van Rossum, R. Delfos, A. Twerda, J. Westerweel

引用次数: 1

Hypersonic boundary-layer instability characterization and transition downstream of distributed roughness 分布粗糙度下高超音速边界层不稳定性特征及过渡

IF 2.4 3区工程技术

Experiments in Fluids Pub Date : 2023-09-23 DOI: 10.1007/s00348-023-03703-x

Yuteng Gui, Chengjian Zhang, Xueliang Li, Duolong Xu, Jie Wu

{"title":"Hypersonic boundary-layer instability characterization and transition downstream of distributed roughness","authors":"Yuteng Gui, Chengjian Zhang, Xueliang Li, Duolong Xu, Jie Wu","doi":"10.1007/s00348-023-03703-x","DOIUrl":"10.1007/s00348-023-03703-x","url":null,"abstract":"<div><p>The ablation of thermal protection systems in hypersonic vehicles would generate randomly distributed surface roughness, which prominently influences laminar-turbulent boundary-layer transition. While discrete and regular-shaped roughness elements have been extensively studied, the effect of distributed roughness on hypersonic boundary-layer stability and transition is poorly understood. In the present study, experiments were performed on a 7-degree half-angle sharp cone with sandpaper-type roughness in a Mach 6 Ludwieg tube. The transition onset locations were obtained by infrared thermography. Single/two-point focused laser differential interferometer was utilized to characterize the instability waves over distributed roughness along both the streamwise and wall-normal directions within the laminar, transitional and turbulent regions. On distributed roughness, the transition onset location moves forward, and the second mode was still the dominant instability. It exhibits lower frequency, faster growth, and earlier decay compared with the smooth surface. Linear stability calculations were carried out to assist with experiments. Furthermore, bispectral analysis indicates complicated nonlinear phase-locked energy exchanges within the boundary layer. It is shown that the earlier saturation and faster decay of the second mode on distributed roughness is associated with intensified nonlinear interactions.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"64 10","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-023-03703-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41079994","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

Force moment partitioning and scaling analysis of vortices shed by a 2D pitching wing in quiescent fluid 静止流体中二维变桨机翼旋涡的力矩划分和比例分析

IF 2.4 3区工程技术

Experiments in Fluids Pub Date : 2023-09-21 DOI: 10.1007/s00348-023-03698-5

Yuanhang Zhu, Howon Lee, Sushrut Kumar, Karthik Menon, Rajat Mittal, Kenneth Breuer

{"title":"Force moment partitioning and scaling analysis of vortices shed by a 2D pitching wing in quiescent fluid","authors":"Yuanhang Zhu, Howon Lee, Sushrut Kumar, Karthik Menon, Rajat Mittal, Kenneth Breuer","doi":"10.1007/s00348-023-03698-5","DOIUrl":"10.1007/s00348-023-03698-5","url":null,"abstract":"<div><p>We experimentally study the dynamics and strength of vortices shed from a NACA 0012 wing undergoing sinusoidal pitching in quiescent water. We characterize the temporal evolution of the vortex trajectory and circulation over a range of pitching frequencies, amplitudes and pivot locations. By employing a physics-based force and moment partitioning method (FMPM), we estimate the vortex-induced aerodynamic moment from the velocity fields measured using particle image velocimetry. The vortex circulation, formation time and vorticity-induced moment are shown to follow scaling laws based on the feeding shear-layer velocity. The vortex dynamics, together with the spatial distribution of the vorticity-induced moment, provide quantitative explanations for the nonlinear behaviors observed in the fluid damping (Zhu et al. in J Fluid Mech, 923:R2, 2021). The FMPM-estimated moment and damping are shown to match well in trend with direct force measurements, despite a discrepancy in magnitude. Our results demonstrate the powerful capability of the FMPM in dissecting experimental flow field data and providing valuable insights into the underlying flow physics.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"64 10","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41080210","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: 1

Identifying dominant flow features from very-sparse Lagrangian data: a multiscale recurrence network-based approach 从非常稀疏的拉格朗日数据中识别主要流量特征：一种基于多尺度递归网络的方法

IF 2.4 3区工程技术

Experiments in Fluids Pub Date : 2023-09-21 DOI: 10.1007/s00348-023-03700-0

Giovanni Iacobello, David E. Rival

{"title":"Identifying dominant flow features from very-sparse Lagrangian data: a multiscale recurrence network-based approach","authors":"Giovanni Iacobello, David E. Rival","doi":"10.1007/s00348-023-03700-0","DOIUrl":"10.1007/s00348-023-03700-0","url":null,"abstract":"<p>Realistic fluid flow problems often require that Lagrangian tracers are deployed in a sparse or very-sparse manner, such as for oceanic and atmospheric flows where large-scale motion needs characterisation. Data sparsity represents a significant issue in Lagrangian analysis, especially for data-driven methods that rely heavily on large datasets. We propose a multiscale spatial recurrence network (MSRN) methodology for characterising very-sparse Lagrangian data, which exploits individual tracks and a spatial recurrence criterion to identify the spatio-temporal complexity of tracer trajectories. The MSRN is an unsupervised modelling framework that does not require <i>a priori</i> parameter setting, and—through the quantification of persistent link activation at specific trajectory intervals—can reveal the presence of dominant looping scales in a variety of salient fluid flows. This new paradigm is shown to be successful for the study of Lagrangian tracers seeded in complex (realistic) flows, including unsteady and advection-dominated problems. This makes MSRNs an effective and versatile tool to characterise sensor trajectories in key problems such as environmental processes critical to understanding and mitigating climate change.</p>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"64 10","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-023-03700-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41080068","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: 2