Mixing dynamics in two-dimensional acceleration-driven compressible flow

The coupled effects of variable density (VD) and flow compressibility on the externally accelerated two-dimensional system are studied with direct numerical simulations (DNS). In this flow configuration, columns of two pure fluids are initially separated by two randomly perturbed thin interfaces parallel to the acceleration field within a neutrally stratified fluid domain with periodic boundary conditions. The fully compressible, multi-species Navier–Stokes equations are solved at various Atwood numbers and isothermal Mach numbers to study the VD effects on compressible acceleration-driven flow. Atwood number represents the normalized molar mass ratio between the mixing fluids, such that a higher number corresponds to a greater difference in molar mass between the mixing fluids. The background isothermal Mach number controls the flow compressibility and is proportional to the square root of the magnitude of the external acceleration field. It is observed that an increase in flow compressibility leads to a slower growth of the shear layer, with this effect becoming more pronounced as the Atwood number increases. In this talk, we will compare the evolution of the shear layer growth, molecular mixing, and enstrophy of the flow for the different DNS cases.