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

{"title":"ON ACCELERATION STATISTICS IN TURBULENT STRATIFIED SHEAR FLOWS","authors":"F. Jacobitz, K. Schneider, M. Farge","doi":"10.1615/tsfp9.560","DOIUrl":"https://doi.org/10.1615/tsfp9.560","url":null,"abstract":"The Lagrangian and Eulerian acceleration statistics in homogeneous turbulence with uniform shear and stable stratification are studied using direct numerical simulations. The Richardson number is varied from Ri = 0, corresponding to unstratified shear flow, to Ri = 1, corresponding to strongly stratified shear flow. The probability density functions (pdfs) of both Lagrangian and Eulerian accelerations show a strong and similar influence on the Richardson number and extreme values for Eulerian acceleration are stronger than those observed for the Lagrangian acceleration. A consideration of the terms in the NavierStokes equation shows that the Lagrangian acceleration is mainly determined by the pressure-gradient, while the Eulerian acceleration is dominated by the nonlinear term. Similarly, the Eulerian time-rate of change of fluctuating density is observed to have larger extreme values than that of the Lagrangian time-rate of change due to the nonlinear term in the advection-diffusion equation for fluctuating density. Hence, the time-rate of change of fluctuating density obtained at a fixed location by an Eulerian observer is mainly due to advection of fluctuating density through this location, while the time-rate of change of fluctuating density following a fluid particle is substantially smaller, and due to production and dissipation of fluctuating density. INTRODUCTION An understanding of the Lagrangian acceleration properties of a fluid particle in turbulent flows is of fundamental importance. After early work by Heisenberg (1948) and Yaglom (1949), recent studies range from theoretical investigations (e.g. Tsinober, 2001) to applications such as the modeling of particle dispersion (e.g. Pope, 1994). This work is carried out using both experimental (e.g. La Porta et al., 2001) as well as computational (e.g. Yeung, 2002; Toschi & Bodenschatz, 2009) approaches. The majority of previous investigations focused on Lagrangian properties of isotropic turbulence. The Lagrangian acceleration was found to be strongly intermittent and heavy tails were observed in its pdf. For example, extreme values as high as 1,500 times the acceleration of gravity were observed for the Lagrangian acceleration of fluid particles (La Porta et al., 2001) and numerical simulations confirmed these results (Toschi & Bodenschatz, 2009). Many applications of Lagrangian dynamics target the transport and mixing of natural and anthropogenic substances in the geophysical environment. Such flows are often characterized by the presence of shear and stratification. Homogeneous turbulent stratified shear flow with constant vertical stratification rate Sρ = ∂ρ/∂y and constant vertical shear rate S = ∂U/∂y represents the simplest flow configuration in order to study the competing effects of shear and stratification. This flow has been investigated extensively in the past: Experimental studies include Komori et al. (1983), Rohr et al. (1988), Piccirillo & Van Atta (1997), and Keller & Va","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena","volume":"61 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":"124048280","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":"BYPASS TRANSITION AND SUBCRITICAL TURBULENCE IN PLANE POISEUILLE FLOW","authors":"S. Zammert, B. Eckhardt","doi":"10.1615/tsfp9.490","DOIUrl":"https://doi.org/10.1615/tsfp9.490","url":null,"abstract":"Plane Poiseuille flow shows turbulence at a Reynolds number that is lower than the critical one for the onset of Tollmien-Schlichting waves. The transition to turbulence follows the same route as the by-pass transition in boundary layers, i.e. finite amplitude perturbations are required and the flow is dominated by downstream vortices and streaks in the transitional regime. In order to relate the phenomenology in plane Poiseuille flow to our previous studies of plane Couette flow (Kreilos & Eckhardt, 2012), we study a symmetric subspace of plane Poiseuille flow in which the bifurcation cascade stands out clearly. By tracing the edge state, which in this system is a travelling wave, and its bifurcations, we can trace the formation of a chaotic attractor, the interior crisis that increase the phase space volume affected by the flow, and the ultimate transition into a chaotic saddle in a crisis bifurcation. After the boundary crisis we can observe transient chaos with exponentially distributed lifetimes.","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127275554","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":"BOUNDARY LAYER STRUCTURE IN TURBULENT RAYLEIGH-BÉNARD CONVECTION IN AIR","authors":"R. D. Puits, C. Willert","doi":"10.1615/tsfp9.1010","DOIUrl":"https://doi.org/10.1615/tsfp9.1010","url":null,"abstract":"We present Particle Image Velocimetry measurements in the boundary layer in turbulent Rayleigh-Benard (RB) convection for the Rayleigh number Ra=1.4×10E10 and the Prandtl number Pr=0.7. The measurements have been undertaken in a large-scale RB experiment 7.15 m in diameter and 6.30 m in height which is called the “Barrel of Ilmenau”. They give detailed insight into the near-wall flow field in turbulent RB convection and provide experimental data to evaluate various competing theories on the heat transport which essentially based on the boundary layer. We found that the convective boundary layer becomes turbulent locally and temporarily although its shear Reynolds number Re_s=(U_infty delta)⁄nu ≈ 265 (U_infty - outer velocity, delta - boundary layer thickness, nu - kinematic viscosity) is considerably smaller than the value 420 underlying existing phenomenological theories.","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125570074","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":"CONVECTION OF MOMENTUM TRANSPORT EVENTS IN A TURBULENT BOUNDARY LAYER","authors":"R. Kat, B. Ganapathisubramani","doi":"10.1615/tsfp9.670","DOIUrl":"https://doi.org/10.1615/tsfp9.670","url":null,"abstract":"","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena","volume":"2012 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125644602","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":"EFFECTS OF SUDDEN CHANGE IN SURFACE ROUGHNESS ON TURBULENT BOUNDARY LAYERS","authors":"R. Hanson, B. Ganapathisubramani","doi":"10.1615/tsfp9.240","DOIUrl":"https://doi.org/10.1615/tsfp9.240","url":null,"abstract":"","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127200711","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 OF THE FLOW IN A TOROIDAL PIPE","authors":"P. Schlatter, J. Canton, R. Oerlue","doi":"10.1615/tsfp9.500","DOIUrl":"https://doi.org/10.1615/tsfp9.500","url":null,"abstract":"While hydrodynamic stability and transition to turbulence in straight pipes - being one of the most fundamental problems in fluid mechanics - has been studied extensively, the stability of curved p ...","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133890936","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":"NEW TURBULENT SCALING LAWS FROM THE MULTI-POINT CORRELATION EQUATIONS","authors":"Andreas Rosteck, M. Oberlack","doi":"10.1615/tsfp9.1080","DOIUrl":"https://doi.org/10.1615/tsfp9.1080","url":null,"abstract":"","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114424990","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":"A COMPARISON OF THE DECAY OF ENERGY IN THE WAKE OF FRACTAL AND CLASSICAL GRIDS","authors":"R. J. Hearst, P. Lavoie","doi":"10.1615/tsfp9.540","DOIUrl":"https://doi.org/10.1615/tsfp9.540","url":null,"abstract":"A square-fractal-element grid and two regular grids, all with the same blockage, are used to investigate how the produced turbulence differs. The square-fractal-element grid is made-up of a 12×8 array of small square fractals mounted to a background mesh. For a constant inlet Reynolds number, ReM , it is found that the turbulent kinetic energy powerlaw decay exponent is comparable for all three grids in the far-field, although the fractal-based grid produces an extended non-equilibrium region relative to the other two grids. The normalized dissipation, Cε , is found to be approximately described by ReM/ReL in the non-equilibrium region, becoming approximately constant in the far-field. A correlation is also found between Cε and normalized Reynolds stress, 〈uv〉/u′v′, across both the non-equilibrium region and the far-field. Finally, non-equilibrium and farfield spectra are compared at fixed Reλ across all three grids. It is found that the far-field spectra are reasonably collapsed for all three grids for a given Reλ . However, if a non-equilibrium spectrum at a location where 〈uv〉 6= 0 is compared at a given Reλ to a far-field spectrum where 〈uv〉 ≈ 0, then the non-equilibrium spectrum is nearer to k−5/3. This result appears to be closely related to the existence of 〈uv〉 that is able to penetrate to scales associated with the scaling range.","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth International Symposium on Turbulence and Shear Flow Phenomena","volume":"31 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":"125064100","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 STUDIES ON OPTIMAL SHAPE OF A SINUSOIDAL RIBLET FOR DRAG REDUCTION IN WALL TURBULENCE","authors":"M. Sasamori, O. Iihama, H. Mamori, K. Iwamoto, A. Murata","doi":"10.1615/tsfp9.860","DOIUrl":"https://doi.org/10.1615/tsfp9.860","url":null,"abstract":"BACKGROUND AND OBJECTIVES Skin friction drag significantly increases in wall turbulence. Techniques for reducing skin friction drag are required to be developed because it is expected to decrease energy costs of transportation equipment. A wellknown method for decreasing skin friction drag is installing streamwise micro grooves on wall surfaces, which are called as ‘riblet surfaces’. Since riblet surfaces can be readily applied to existing equipments, so many types of ‘twodimensional riblet shapes’ (refereed as 2-D riblets, hereafter) have been performed and their drag reduction effects have been confirmed, e.g., Walsh (1980); Bechert et al. (1997); Choi (1989). Here, the ‘2-D’ means that the riblets are aligned in the streamwise direction. The shape of 2-D riblets has been optimized, of which drag reduction rate is approximately 10% (Bechert et al., 1997). The optimized 2-D riblet is a blade-type with very thin adjacent walls, and the lateral spacing is smaller than the diameter of streamwise vortices. Choiet al. (1993) reported that the riblet affects ejection and sweep events and inhibits streamwise vortices approaching to near-wall regions, because the lateral spacing of the riblet is smaller than the diameter of streamwise vortices. However, riblet surfaces with higher drag reduction effect are required in order to apply riblets in practical applications, because decrease in fuel costs by the abovementioned drag reduction effect was not sufficient to cover maintenance costs of the riblet (Viswanath, 2002). Instead of 2-D riblets, three-dimensional riblet surfaces (3-D riblets) have also been investigated in order to obtain higher drag reduction. The ‘3-D’ means that a riblet shape varies in the streamwise direction. One of expected riblet shapes is a wavy riblet suggested by Peet & Sagaut (2009). They aimed to obtain an effect similar to spanwise wall oscillation technique, e.g., Choi & Graham (1998). They found 7.4% drag reduction rate and concluded that decrease of crossflow turbulence contributes to drag reduction. As best of author’s knowledge, obtained drag reduction rates by 3-D riblets, however, are smaller than that by the optimized 2-D riblet. It is because an optimization of the shape of 3-D riblets is difficult due to many parameters of the shape as compared with those of 2-D riblet.","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth 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":"125892807","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":"EXPLORING THE INTERACTION OF RED BLOOD CELL ANALOGS WITH TURBULENCE USING PARTICLE TRACKING VELOCIMETRY","authors":"S. Rahgozar, G. Rosi, Lucie Kaucky, A. Walker, D. Rival","doi":"10.1615/tsfp9.1230","DOIUrl":"https://doi.org/10.1615/tsfp9.1230","url":null,"abstract":"","PeriodicalId":196124,"journal":{"name":"Proceeding of Ninth 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":"125581378","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}