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

TRACKING COHERENT STRUCTURES IN MASSIVELY-SEPARATED AND TURBULENT FLOWS 在大规模分离和湍流中跟踪相干结构

Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena Pub Date : 2018-01-29 DOI: 10.1103/PHYSREVFLUIDS.3.014702

Matthew Rockwood, Yangzi Huang, Melissa A. Green

{"title":"TRACKING COHERENT STRUCTURES IN MASSIVELY-SEPARATED AND TURBULENT FLOWS","authors":"Matthew Rockwood, Yangzi Huang, Melissa A. Green","doi":"10.1103/PHYSREVFLUIDS.3.014702","DOIUrl":"https://doi.org/10.1103/PHYSREVFLUIDS.3.014702","url":null,"abstract":"Coherent vortex structures are tracked in simulations of massively-separated and turbulent flows. Topological Lagrangian saddle points are found using intersections of the positive and negative finite-time Lyapunov exponent (FTLE) ridges, and these points are then followed in order to track individual coherent structure motion in both a complex interacting three-dimensional flow (turbulent channel) and during vortex formation (two-dimensional bluff body shedding). For a simulation of wall-bounded turbulence in a channel flow, tracking Lagrangian saddles shows that the average structure convection speed exhibits a similar trend as a previously published result based on velocity and pressure correlations, giving validity to the method. When this tracking method is applied in a study of a circular cylinder in cross-flow it shows that Lagrangian saddles rapidly accelerate away from the cylinder surface as the vortex sheds. This saddle behavior is compared with the time-resolved static pressure distribution on the circular cylinder, yielding locations on a cylinder surface where common sensors could detect this phenomenon, which is not available from force measurements or vortex circulation calculations. The current method of tracking coherent structures yields insight into the behavior of the coherent structures in both of the diverse flows presented, highlighting the breadth of its potential application.","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena","volume":"400 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122173143","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}

引用次数: 14

INNER-OUTER INTERACTIONS IN A TURBULENT BOUNDARY LAYER OVERLYING COMPLEX ROUGHNESS 复杂粗糙度上紊流边界层的内外相互作用

Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena Pub Date : 2015-11-24 DOI: 10.1103/PHYSREVFLUIDS.2.044603

G. Pathikonda, K. Christensen

{"title":"INNER-OUTER INTERACTIONS IN A TURBULENT BOUNDARY LAYER OVERLYING COMPLEX ROUGHNESS","authors":"G. Pathikonda, K. Christensen","doi":"10.1103/PHYSREVFLUIDS.2.044603","DOIUrl":"https://doi.org/10.1103/PHYSREVFLUIDS.2.044603","url":null,"abstract":"Hot-wire measurements were performed in turbulent flow overlying a smooth and a rough wall (the latter a multiscale topography) with the intent of investigating the details of inner–outer interactions. One-point measurements with a traversing probe were made to investigate the distribution of streamwise turbulent kinetic energy and large scale–small scale interactions at different regions of the smoothand rough-wall cases. In addition, 2-probe simultaneous measurements were conducted and enabled investigation of inner–outer interactions wherein the large scales were always sampled in the outer layer. After identifying different regions across the boundary layer in the timedelayed correlation maps of the amplitude modulation coefficient, roughness-induced changes to the near-wall behavior were investigated. It was observed that the amplitude modulation influence on the near-wall small scales by the large scales in logarithmic region appears augmented in the rough-wall case compared to smooth-wall flow. Further, among the different spanwise positions investigated over the complex roughness (previously found to induce persistent secondary flows owing to spanwise heterogeneity of the topography), the low-momentum pathway region tended to have a ‘stronger’ interaction compared to the high-momentum pathway position.","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena","volume":"113 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134328337","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}

引用次数: 41

SKIN-FRICTION DRAG REDUCTION USING THE METHOD OF SPANWISE MEAN VELOCITY GRADIENT 用展向平均速度梯度法进行表面摩擦减阻

Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena Pub Date : 2015-11-23 DOI: 10.1615/tsfp9.880

B. Fallenius, S. S. Sattarzadeh, R. Downs, S. Shahinfar, J. Fransson

引用次数: 0

PLANE TURBULENT COUETTE FLOW: DNS, LARGE SCALE STRUCTURES AND SYMMETRY INDUCED SCALING LAWS 平面湍流库埃特流:dns、大尺度结构和对称诱导标度定律

Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena Pub Date : 2015-07-02 DOI: 10.1615/tsfp9.1040

V. Avsarkisov, M. Oberlack, S. Hoyas, Andreas Rosteck, J. P. Garcia-Galache, A. Frank

引用次数: 0

SMALL-SCALE PHASE ORGANIZATION THROUGH LARGE-SCALE INPUTS IN A TURBULENT BOUNDARY LAYER 湍流边界层中通过大尺度输入的小尺度相组织

Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena Pub Date : 2015-07-01 DOI: 10.1615/tsfp9.440

S. Duvvuri, B. McKeon

引用次数: 3

A NEW DOUBLE-SLIT CURVED WALL-JET (CWJ) BURNER FOR STABILIZING TURBULENT PREMIXED AND NON-PREMIXED FLAMES 一种用于稳定湍流预混和非预混火焰的新型双缝弯曲壁面射流燃烧器

Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena Pub Date : 2015-06-30 DOI: 10.1615/tsfp9.130

M. S. Mansour, S. Chung

{"title":"A NEW DOUBLE-SLIT CURVED WALL-JET (CWJ) BURNER FOR STABILIZING TURBULENT PREMIXED AND NON-PREMIXED FLAMES","authors":"M. S. Mansour, S. Chung","doi":"10.1615/tsfp9.130","DOIUrl":"https://doi.org/10.1615/tsfp9.130","url":null,"abstract":"A novel double-slit curved wall-jet (CWJ) burner was proposed and employed, which utilizes the Coanda effect by supplying fuel and air as annular-inward jets over a curved surface. We investigated the stabilization characteristics and structure of methane/air, and propane/air turbulent premixed and non-premixed flames with varying global equivalence ratio,  , and Reynolds number, Re. Simultaneous time-resolved measurements of particle image velocimetry and planar laser-induced fluorescence of OH radicals were conducted. The burner showed potential for stable operation for methane flames with relatively large fuel loading and overall rich conditions. These have a non-sooting nature. However, propane flames exhibit stable mode for a wider range of equivalence ratio and Re. Mixing characteristics in the cold flow of non-premixed cases were first examined using acetone fluorescence technique, indicating substantial transport between the fuel and air by exhibiting appreciable premixing conditions. PIV measurements revealed that velocity gradients in the shear layers at the boundaries of the annular jets generate the turbulence, enhanced with the collisions in the interaction jet, IJ, region. Turbulent mean and rms velocities were influenced significantly by Re and high rms turbulent velocities are generated within the recirculation zone improving the flame stabilization in this burner. Premixed and non-premixed flames with high equivalence ratio were found to be more resistant to local extinction and exhibited a more corrugated and folded nature, particularly at high Re. For flames with low equivalence ratio, the processes of local quenching at IJ region and of re-ignition within merged jet region maintained these","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117105789","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}

引用次数: 0

TURBULENT MIXING IN CROSS SHEARED STRATIFIED FLOW 横剪分层流中的湍流混合

Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena Pub Date : 2015-06-30 DOI: 10.1615/tsfp9.780

Y. Xiao, Wenxian Lin, J. McCormack, Yinghe He, S. Armfield, M. Kirkpatrick

{"title":"TURBULENT MIXING IN CROSS SHEARED STRATIFIED FLOW","authors":"Y. Xiao, Wenxian Lin, J. McCormack, Yinghe He, S. Armfield, M. Kirkpatrick","doi":"10.1615/tsfp9.780","DOIUrl":"https://doi.org/10.1615/tsfp9.780","url":null,"abstract":"Cross sheared stratified (CSS) flow, in which the horizontal streamwise and spanwise basic sheared flow components interact with each other in a stratified environment, are studied with direct numerical simulation. The cross shear ratio xi, defined as ξ = Dv0/Du0 where Du0 and Dv0 are the respective velocity changes across the heared/stratified layer in the streamwise and spanwise directions, is introduced for CSS flow. The coherent structures of CSS flow are examined for ξ = 0 ~ 1 and Ri = 0.01 ~ 0.2, where Ri is the bulk Richardson number. It is found that in a weakly stratified environment with Ri = 0.01, a significant increase of the magnitude of the mixedness thickness dm is observed from its time series for CSS flow compared to that for parallel sheared stratified flow. Three CSS instability modes, i.e. , a 'streamwise dominant' mode, a 'balanced' mode and a 'spanwise dominant' mode, are identified, which differ from each other with different interaction behaviors between the spanwise 'eddy wrap' structures and the classic streamwise 'cat eye' eddies of the Kelvin-Helmholtz instability. The results also show that in a strongly stratified environment with Ri=0.1-0.2, the eddy-featured coherent structures progressively decay into the wave-like structures, and the normalized mixedness thickness dq /dq ,Ri=0.01 is found to decrease as an exponential function of increasing Ri at the turbulence stage.","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena","volume":"81 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124524363","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}

引用次数: 0

ANALOGY BETWEEN SCALAR AND VELOCITY FLUCTUATIONS IN A SLIGHTLY HEATED AXISYMMETRIC MIXING LAYER 微加热轴对称混合层中标量波动与速度波动的类比

Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena Pub Date : 2015-06-30 DOI: 10.1615/tsfp9.220

F. Thiesset, V. Schaeffer, R. Antonia, L. Djenidi, L. Danaila

引用次数: 0

COHERENT VORTICITY IN TURBULENT CHANNEL FLOW: A WAVELET VIEWPOINT

Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena Pub Date : 2015-06-30 DOI: 10.1615/tsfp9.730

K. Yoshimatsu, Teluo Sakurai, K. Schneider, M. Farge, K. Morishita, T. Ishihara

引用次数: 1

STOCHASTIC FLUID DYNAMIC MODEL AND DIMENSIONAL REDUCTION 随机流体动力学模型与降维

Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena Pub Date : 2015-06-30 DOI: 10.1615/tsfp9.1090

V. Resseguier, É. Mémin, B. Chapron

引用次数: 3