Direct numerical simulations of shocklet-containing turbulent channel counter-flows

TL;DR

This study uses direct numerical simulations to explore high Mach number turbulent channel flows with shocklets, revealing how compressibility influences turbulence structures and dissipation.

Contribution

It extends previous work by simulating higher Mach numbers and lower Prandtl numbers to analyze shocklet formation and turbulence asymmetry.

Findings

Presence of shocklets in high Mach number turbulence

Limited dilatational dissipation at peak turbulent Mach number

Asymmetry in probability density functions of dilatation

Abstract

Counter-flow or counter-current configurations can maintain high turbulence intensities and exhibit a significant level of mixing. We have previously introduced a wall-bounded counter-flow turbulent channel configuration (Physical Review Fluids, 6(9), p.094603.) as an efficient framework to study compressibility effects on turbulence. Here, we extend our previous direct numerical simulation study to a relatively higher Mach number (M=0.7) to investigate strong compressibility effects (also by reducing the Prandtl number from Pr=0.7 to 0.2), and the formation and evolution of unsteady shocklet structures. It is found that the configuration is able to produce highly turbulent flows with embedded shocklets and significant asymmetry in probability density functions of dilatation. A peak turbulent Mach number close to unity is obtained, for which the contribution of the dilatational dissipation to total dissipation is nevertheless found to be limited to 6%.