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Friday, November 09, 2018
10:00 AM - 11:00 AM
Los Alamos Research Park, 2nd floor, Camelina Room

Seminar

Numerical Study of Variable Density Flow Interaction with a Normal Shock Wave

Yifeng Tian
Michigan State University

Accurate numerical simulations of Shock-Turbulence Interaction (STI) are conducted by a hybrid monotonicity preserving-compact finite difference scheme for a detailed study of STI in variable density flows. Theoretical and numerical assessments of data confirm that all turbulence scales as well as the STI are well captured by the computational method. Linear Interaction Approximation (LIA) convergence tests are conducted to show that shock-capturing simulations exhibit similar converging trend to LIA predictions as shock-resolving Direct Numerical Simulations (DNS), but the mesh can be coarser than that normally used in shock-resolving DNS. The effects of density variations on STI are studied by comparing the results corresponding to an upstream multi-fluid mixture with the single-fluid ones. The results show that for parameter ranges considered in this study, turbulence amplification by the normal shock wave is much higher and the reduction in turbulence length scales is more significant when strong density variations exist. Turbulent mixing enhancement by the shock is also observed to be higher and stronger mixing asymmetry in the post-shock region is observed in the variable density flow. The turbulence structure is strongly modified by the shock wave, with a differential distribution of turbulent statistics in regions with different densities. The dominating mechanisms behind STI influence on mixing are identified by analyzing the transport equations for the Reynolds stresses, vorticity, normalized mass flux and density specific volume covariance. The statistics of velocity gradient tensor (VGT) are examined with both Eulerian and Lagrangian methods to further examine the important variable density effects on the post-shock turbulence structure.

[1] Tian, Y., Jaberi, F.A., Li, Z. and Livescu, D., 2017. Numerical study of variable density turbulence interaction with a normal shock wave. Journal of Fluid Mechanics, 829, pp.551-588.[2] Tian, Y., Jaberi, F.A. and Livescu, D., 2018. Density effects on the post-shock turbulence structure and dynamics. Journal of Fluid Mechanics. (submitted)

Host: Michael Chertkov