Turbulence at the edge of continuum

Abstract

For high-Mach-number turbulent flows, the Kolmogorov length scale can be comparable to the gas-molecule mean-free path, which could introduce noncontinuum molecular-level effects into the turbulent energy cascade. To investigate this issue, compressible Taylor-Green vortex flow is simulated using both noncontinuum molecular gas dynamics and continuum computational fluid dynamics. Although the energy-decay rates are the same, molecular-level fluctuations break the flow symmetries and thereby produce different but statistically similar routes from the initial nonturbulent flow to the long-time turbulent flow.