Bulletin of the American Physical Society
76th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 19–21, 2023; Washington, DC
Session R02: Turbulence: Shear Layers 
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Chair: Katepalli Sreenivasan, New York University Room: Ballroom B 
Monday, November 20, 2023 1:50PM  2:03PM 
R02.00001: Dense gas effects on turbulent fluctuations of compressible turbulent shear layer Steven Dai, Hang Song, Anjini Chandra, Sanjiva K Lele

Monday, November 20, 2023 2:03PM  2:16PM 
R02.00002: Coherent Motions and Mixing Dynamics of SingleStream Shear Layers: Insights from 4DPTV Measurements Ankit K Gautam, Daniel Livescu, Ricardo MejiaAlvarez The present study addresses the need for comprehensive volumetric measurements within a singlestream shear layer (SSSL), with the aim of advancing our understanding of intrinsic flow dynamics. A 4DPTV technique is employed to capture the separation of a wall boundary layer and its subsequent development into a selfsimilar SSSL. The separation region is characterized by viscous domination and a negative production rate, which is further corroborated by a turbulent kinetic energy budget analysis. An evaluation of the statistical flow descriptors shows selfsimilarity achieved at a significantly shorter distance ≈60θ_{0} (θ_{0}: initial momentum thickness), contrasting with the past reports. Moreover, a comparison of shear layer width, momentum, and vorticity thickness growth rates with literature reports raises intriguing questions about the potential universality of the growth rate scaling for single and twostream shear layers. Phaseaveraged maps underline the importance of rollupbraid intersection regions as highproduction regions. Additionally, the outer edges of coherent regions exhibit peak production, vortex cores favor higher dissipation rates, and the braid region acts as an energy conduit between contiguous rollups. 
Monday, November 20, 2023 2:16PM  2:29PM 
R02.00003: On the experimental study of 3D turbulent shear layers Dipendra Gupta, Vedant Kumar, Johan Larsson, Gregory P Bewley Turbulent mixing layers are formed when parallel streams flowing at different speed merge. In the usual laboratory model, the mean flow varies mainly in the directions of the velocity difference and flow convection, with no significant changes in the other direction. However, real flows are three dimensional (3D)−the incoming flows are not parallel and have not only different speeds but also different directions, thereby giving rise to 3D turbulent shear layers, i.e., skewed mixing layers, the detailed quantitative study of which is missing. Flow skewing in turbulent boundary layers is reported to cause a reduction in Reynolds stresses and drag. We experimentally investigated the mean flow and statistics of skewed mixing layers in a wind tunnel to find out if similar effects prevail. We generated 3D shear layers by skewing the mean flow with turning vanes at the trailing edge of a splitter plate, and used pitotstatic tubes and xwires to probe the flow at different cross, span and downstream distances. Preliminary results show that skewed mixing layers, like their 2D counterpart, also spread linearly with downstream distance, and that an approx. homogenous shear develops further downstream. At the resolution of our current measurements, the shear layer thickness and shear rate seem not to depend strongly on skewing of the flow. We seek an explanation for this in the turbulence statistics. Understanding the effect of three dimensionality on mixing layers will help us improve designs of engineering structures. 
Monday, November 20, 2023 2:29PM  2:42PM 
R02.00004: Threedimensional effects in turbulent shear layers Vedant Kumar, Dipendra Gupta, Gregory P Bewley, Johan Larsson The skewing of mean flow in canonical turbulent boundary layers is known to cause a reduction 
Monday, November 20, 2023 2:42PM  2:55PM 
R02.00005: Revisiting Taylor's Hypothesis in Homogeneous Turbulent Shear Flow Frank G Jacobitz, Kai Schneider Taylor’s Hypothesis of frozen flow has frequently been used to convert temporal experimental measurements into a spatial domain and its validity is of 
Monday, November 20, 2023 2:55PM  3:08PM 
R02.00006: Numerical Study of Variable Density Effects on a Spatially Developing Supersonic Turbulent Shear Layer Muhammad Rubayat Bin Shahadat, Zhaorui Li, Farhad A Jaberi, Daniel Livescu Direct Numerical Simulations of a spatially developing supersonic turbulent shear layer have been conducted for different density Atwood numbers to examine the combined effects of compressibility and multifluid global density variation on the shear layer growth rate, turbulence statistics, selfsimilarity, and flow asymmetry. The selfsimilar region of the simulated shear layer is identified by the convergence of normalized streamwise velocity and density profiles, constant peak of Reynolds stress components, and linear growth rate of momentum thickness and shear layer thickness. Introducing global density variation in the multifluid flow enhances the layer asymmetry as compared to the singlefluid shear layer, meaning that the shear layer centerline and peak of Reynolds stresses shift more towards the lighter fluid side. Apart from enhanced asymmetry, the increase in global density variation or the ratio of freestream fluid densities causes more reduction in shear layer growth rate. Comparative study of the effects of compressibility and global density change on flow variables like mean density or crossstream velocity reveals some of the interesting features of the simulated compressible multifluid shear layer. Despite significant differences in lower and higher order statistics at different density Atwood numbers, the mean flow profiles collapse within the selfsimilar zone using our suggested selfsimilar scaling.

Monday, November 20, 2023 3:08PM  3:21PM 
R02.00007: Abstract Withdrawn

Monday, November 20, 2023 3:21PM  3:34PM 
R02.00008: Mixing in stratified shear turbulence: implications for the Saharan Air Layer Rodrigo Rodakoviski, Marcelo Chamecki

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