Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena最新文献

{"title":"PROPER ORTHOGONAL DECOMPOSITION ON COMPRESSED DATA","authors":"O. Marin, E. Merzari, P. Schlatter, Andrew R. Siegel","doi":"10.1615/tsfp10.80","DOIUrl":"https://doi.org/10.1615/tsfp10.80","url":null,"abstract":"The main approach to identifying coherent structures in a flow field is the Proper Orthogonal Decomposition, due to its simplicity and effectiveness. However it is a data intensive method which bec ...","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122101302","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"IMAGE-BASED MODELING OF THE SKIN-FRICTION COEFFICIENT IN COMPRESSIBLE BOUNDARY-LAYER TRANSITION","authors":"Wenjie Zheng, Yue Yang, Shiyi Chen","doi":"10.1615/tsfp10.990","DOIUrl":"https://doi.org/10.1615/tsfp10.990","url":null,"abstract":"","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129614475","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Large-eddy simulation of flow over a circular cylinder in the sub-critical regime","authors":"W. Cheng, D. Pullin, R. Samtaney","doi":"10.1615/tsfp10.1200","DOIUrl":"https://doi.org/10.1615/tsfp10.1200","url":null,"abstract":"","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129470225","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"THE PERFORMANCE OF A NEW IMMERSED BOUNDARY METHOD ON SIMULATING UNDERWATER LOCOMOTION AND SWIMMING","authors":"A. Hemmati, Utku Senturk, T. Buren, A. Smits","doi":"10.1615/tsfp10.410","DOIUrl":"https://doi.org/10.1615/tsfp10.410","url":null,"abstract":"We report the benchmark results of a new Immersed Boundary Method (IBM) incorporated into Direct Numerical Simulation (DNS) of a pitching panel, representing fishlike swimming, using foam-extend-3.2. The panel is flat and thin, and it has a triangular (convex) trailing edge, similar to that seen in the caudal fin of some fish. The accuracy of the solver is verified by comparing four cases of bluff body wake simulations with reported experimental and numerical studies. For example, the structure of the mean wake compared well with that obtained using PIV in a companion experiment. The differences in thrust generation and propulsion efficiency of square and convex thin panels are examined to identify the effect of trailing edge shape using proper orthogonal decomposition. The effect of Reynolds number is also evaluated by comparing the wake at Reynolds numbers of 2,000 and 10,000. INTRODUCTION Many biological species have evolved to develop efficient propulsive systems for swimming that also exhibit high speed and maneuverability (Sambiley, 1990; Sumich & Morrissey, 2004). Understanding the mechanics of aquatic propulsion has attracted the attention of many researchers over the years. Such explorations can yield valuable information on designing energy efficient and fast systems with high maneuverability and stealth that match and possibly surpass the performance of biological species. In this regard, it is often useful to focus on simple systems that can be used to study fundamental aspects of swimming performance. For instance, the implications of the trailing-edge shape of a tail fin as well as its orientation and movement (that is, harmonic fin motion) on the formation of vortex structures, wake dynamics and thrust generation plays a dominant role in understanding physics of fish-like swimming (Van Buren et al., 2016). The oscillating motion of a NACA 0012 airfoil was studied by Triantafyllou et al. (1991) as a representative of swimming motion by fish, which demonstrated a maximum propulsive efficiency of 25% for the Strouhal number St = 0.25− 0.35, where St = fpc/U , fp is the frequency of oscillation, c is the fin characteristic length, and U is the swimming speed. The extensive study by Buchholz & Smits (2006) on the wake of a pitching rigid rectangular panel at moderate Reynolds numbers (Re =Uc/ν) revealed that the flow is dominated by horseshoe-like structures. The aspect ratio of the panel was identified to impact the wake, and thus, the propulsive performance efficiency, which ranged from 9%− 21%. Green & Smits (2008) investigated the distribution of pressure on the pitching panel, which revealed that the favorable streamwise pressure gradient that is present over most of the panel reversed near the trailing edge. There are many experimental challenges, however, in determining detailed surface pressure distributions in unsteady wakes, and it is even more difficult to determine the instantaneous shear stress distributions. In contrast, c","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130490966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Linear stability analysis of turbulent flows over dense filament canopies","authors":"Akshath Sharma, G. Gómez-de-Segura, R. García-Mayoral","doi":"10.1615/tsfp10.900","DOIUrl":"https://doi.org/10.1615/tsfp10.900","url":null,"abstract":"The aim of this work is to study the effect of the variation in canopy parameters on the Kelvin-Helmholtz-like instabilities triggered over them. The appearance of these instabilities over filament canopies has been widely studied, but the present work seeks to explore whether the instability can be manipulated by changing canopy properties. To this effect, a parametric study using linear stability analysis is conducted. For the analyses, the canopy is modelled using two methods. The first models the canopy as a permeable substrate. The second accounts for the canopy through drag forces acting on the flow within it. Some effects of canopy dynamics, namely the average bending of the canopy elements and the dynamic clustering of the canopy are also individually studied. Using the porous medium analogy it is shown for rigid canopies that the onset of the instabilities is governed by the geometric mean of the streamwise and wall-normal permeabilities The drag model exhibits an additional feature missed by the porous model i.e. an optimum value of drag coefficient at which the amplification of the instability is maximum. It is also observed that the clustering of filaments caused by the waving of the canopy can significantly increase the amplification of the instability, and has a greater impact than the mean filament bending.","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"130 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127568047","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of a propulsive jet on the wake-flow structure of an axisymmetric space-launcher model","authors":"A. Schreyer","doi":"10.1615/tsfp10.820","DOIUrl":"https://doi.org/10.1615/tsfp10.820","url":null,"abstract":"The wake flow of a classical space launcher is dominated by the abrupt decrease in diameter at the junction between main body and rocket engine. At this discontinuity, the turbulent boundary layer on the main body separates, a shear layer starts to develop, and a large recirculation region forms downstream of the step. This separation-dominated flow field is highly unsteady and induces strong wall-pressure oscillations, which can excite structural vibrations detrimental to the launcher (Deprés et al. (2004)). The conditions and topology of the wake flow vary strongly along the flight trajectory of the launcher. Especially the influence of the propulsive jet, which becomes increasingly underexpanded with altitude, has a strong influence. The afterexpanding jet plume has a strong displacement effect on the outer flow, which enlarges the recirculation region. Depending on the conditions, the flow may not reattach on the nozzle fairing, potentially allowing hot exhaust gases from the engine nozzle to be convected upstream and harm the structure. Understanding this flow field is thus crucial to minimize those detrimental effects, ultimately contributing to more efficient launcher designs and thus affordable access to space. In the present study, we investigate the influence of an afterexpanding propulsive jet on the wake flow of a generic axisymmetric space-launcher model at a Mach number of M = 2.9 and a Reynolds number of ReD = 1.3 ·106, based on model diameter D. The propulsive jet is simulated with a cold air jet, exiting the integrated TIC-nozzle with a Mach numer of 2.5. The description and discussion of turbulent structures in the wake flow, as well as the influence of a propulsive jet on their dynamic behavior is the focus of this study. The mean and turbulent flow topology and the dynamics of the wake are analyzed based on experimental data from Particle Image Velocimetry (PIV) measurements, Schlieren visualizations, and measurements of surface-pressure fluctuations. The data are interpreted with a combination of classical statistical analysis and post processing by means of Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD). By combining the strengths of these different methods, we intend to improve the understanding of the mechanisms in the wake instability. In particular, we discuss the influence of the jet plume on the growth of vortices in the shear layer forming at the shoulder of the main body. Previous studies observed that the presence of a propulsive jet has a stabilizing effect on the wake. This particularly manifests itself in lower turbulent intensities of the velocity components in the near wake (see also Fig. 1). From our observations within this study, we conclude that several reasons contribute to this stabilizing effect: The width of the shear layer is restricted by the displacement effect exerted by the jet plume. This restricts the maximum size of the vortices in the shear layer. Due to the displace","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127055680","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental and Numerical Investigation of the Oscillation of an Inverted Flag","authors":"Samson Annapureddy, S. Acharya, A. Gilmanov, H. Stolarski","doi":"10.1615/tsfp10.180","DOIUrl":"https://doi.org/10.1615/tsfp10.180","url":null,"abstract":"","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130200118","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modeling momentum and scalar transport in a wall-bounded turbulent flow","authors":"T. Saxton-Fox, B. McKeon","doi":"10.1615/tsfp10.770","DOIUrl":"https://doi.org/10.1615/tsfp10.770","url":null,"abstract":"A mildly-heated turbulent boundary layer was studied to characterize the relationship between velocity structures and the scalar field. Particle image velocimetry (PIV) and a Malley probe (Malley et al., 1992) were used to simultaneously measure the velocity field and the streamwise gradients of the scalar field (Gordeyev et al., 2014) respectively. Two distinct velocity scales were identified to be correlated to scalar mixing by conditionally averaging the velocity field on the existence of a scalar gradient. Resolvent analysis was used to create simple models of these velocity scales (McKeon and Sharma, 2010) and to probe their interaction. Using a combination of structural conditional averaging and conditional averaging on the scalar gradient, significant interaction was observed between the two scales of interest, with behavior consistent with the general scale interaction described by amplitude modulation (Hutchins and Marusic, 2007). The study constructed a model of the velocity field that was correlated to streamwise scalar gradients in the outer boundary layer.","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128855686","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"THE ROLE OF VORTICITY IN TURBULENT, RECTANGULAR, FREE AND WALL JETS","authors":"T. Panidis, A. Pollard","doi":"10.1615/tsfp10.960","DOIUrl":"https://doi.org/10.1615/tsfp10.960","url":null,"abstract":"Experimental results on the near field development of a rectangular jet with aspect ratio 10 are presented. The jet issues from a sharp-edged orifice attached to a rectangular settling chamber at ReDh ~ 42,000 either in free space or parallel to a flat wall. Measurements on cross plane grids obtained with a twocomponent hot wire anemometry probe, provide information on the three-dimensional characteristics of the flow field. Data were suitably averaged over the symmetrical areas of each cross section. Mean vorticity components and terms of the axial vorticity equation were estimated by interpolation and derivation of the mean velocity measurements. Key features of this type of jet are saddleback mean axial velocity profiles and a predominant dumbbell shape of the axial mean velocity contours. These characteristics are found to be influenced by the axial vorticity distribution, which is related to two terms in the axial mean vorticity transport equation that diffuse fluid from the center of the jet towards its periphery. INTRODUCTION Rectangular free and wall jets have attracted the interest of researchers for many years, since they belong to a class of shear flows which is important for understanding the fundamentals of turbulence but also constitute a generic flow configuration in engineering applications. In the past, experimental studies focussed on the global characteristics of jet velocity decay, growth, the entrainment process and the shape of the mean and turbulent profiles up to the self-similarity zone, while more recent studies focus on the influence of specific inlet and boundary conditions, including aspect ratio, nozzle exit geometry and external boundaries along with the Reynolds number on jet development (see Vouros et al. 2015 and Agelin-Chaab, 2010 for recent reviews). Rectangular free and wall jets present important three dimensional characteristics and although quite early Launder and Rodi (1983) noticed the importance of variables such as the axial vorticity, the available experimental information is rather scarce. Nowadays, it is clear that in order to capture the 3D characteristics of rectangular jets, measurements of the velocity and the vorticity in a volume, i.e. on suitable cross plane grids are required. In this work measurements of the three velocity components, obtained with X-probe hot wire anemometry, on cross plane grids in a free and a wall jet (Schwab, 1986), are further exploited using modern interpolation techniques. The jets are issuing under identical conditions from a 1:10 aspect ratio, sharp-edged, rectangular orifice, at Reh ~ 23,000 based on slot height, h (ReDh ~ 42,000, based on the hydraulic diameter, Dh), indicating that the jets should be fully turbulent, at least beyond the near field (Dimotakis, 2000, Fellouah and Pollard, 2009). The expected symmetries of the distributions are imposed on the experimental data by suitable averaging, taking into account the symmetry properties of each variable. Mean","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126755423","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Measurements of velocity and concentration in a high Reynolds number turbulent boundary layer","authors":"K. Talluru, C. Hernandez-Silva, J. Philip, K. Chauhan","doi":"10.1615/tsfp10.780","DOIUrl":"https://doi.org/10.1615/tsfp10.780","url":null,"abstract":"Measurements of velocity and concentration fluctuations for a horizontal plume released at eight different heights within a turbulent boundary layer (TBL) are discussed in this paper. Most previous studies have reported measurements for the source height limited to s z / δ ≤ 0 . 2 ( s z is the source height and δ is the boundary layer thickness). Here we examine concentration fluctuations when the plume is released in the logarithmic and outer regions of a TBL in order to understand the role of large-scale structures in the transport of scalar quantities. The wall-normal distributions of mean and vari-ance of concentration fit well with the reflected-Gaussian model as previously reported by Fackrell & Robins (1982). A comparison of autocorrelation functions reveals that the integral time scale of the corresponding concentration fluctuations is approximately ten times smaller than the integral time scale of streamwise velocity. Further, it is observed that streamwise scalar flux and cross-correlation coefficient between large-scale velocity and concentration have similar behaviour, i.e., they are positively correlated below and negatively correlated above the plume centreline.","PeriodicalId":266791,"journal":{"name":"Proceeding of Tenth International Symposium on Turbulence and Shear Flow Phenomena","volume":"72 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126530693","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}