Direct numerical simulation of passive scalar in decaying compressible turbulence

The passive scalars in the decaying compressible turbulence with the initial Reynolds number (defined by Taylor scale and RMS velocity) Re=72, the initial turbulent Mach numbers (defined by RMS velocity and mean sound speed) Mt=0.2–0.9, and the Schmidt numbers of passive scalar Sc=2–10 are numerically simulated by using a 7th order upwind difference scheme and 8th order group velocity control scheme. The computed results are validated with different numerical methods and different mesh sizes. The Batchelor scaling withk ⁻¹ range is found in scalar spectra. The passive scalar spectra decay faster with the increasing turbulent Mach number. The extended self-similarity (ESS) is found in the passive scalar of compressible turbulence.