Direct Numerical Simulation of Passive Scalar Mixing in Shock Turbulence Interaction

Passive scalar mixing in the canonical shock-turbulence interaction configuration is investigated through shock-capturing Direct Numerical Simulations (DNS). Scalar fields with different Schmidt numbers are transported by an initially isotropic turbulent flow field passing across a nominally planar shock wave. A solution-adaptive hybrid numerical scheme on Cartesian structured grids is used, that combines a fifth-order WENO scheme near shocks and a sixth-order central-difference scheme away from shocks. The simulations target variations in the shock Mach number, $M$ (from $1.5$ to $3$), turbulent Mach number, $M_t$ (from 0.1 to 0.4, including wrinkled- and broken-shock regimes), and scalar Schmidt numbers, $Sc$ (from 0.5 to 2), while keeping the Taylor microscale Reynolds number constant ($Re_{\lambda}\approx40$). The effects on passive scalar statistics are investigated, including the streamwise evolution of scalar variance budgets, pdfs and spectra, in comparison with their temporal evolution in decaying isotropic turbulence.