Mixing Enhancement of Compressible Planar Mixing Layer Impinged by Oblique Shock Waves

Abstract

This paper presents the mixing enhancements of a spatially developing planar mixing layer interacting with an oblique shock wave by means of large-eddy simulation. The large-scale coherent vortices are found to be modulated by the oblique shock, which results in enhanced vorticity of the vortices. The thickness of the mixing layer impinged by oblique shock waves first decreases due to the increased compressibility effects of the shock wave, but then it increases and finally exceeds that of the shock-free mixing layer because of an accelerating growth rate larger than 0.05. The fluctuating levels of velocities and turbulent kinetic energy are strengthened in the shock–mixing-layer flows. The production term in the Reynolds stress transport equation dominates the increase of the transverse component of the Reynolds normal stresses, whereas the pressure–strain term decreases them and redistributes the energy to the streamwise component in shock–mixing layers, which then leads to the mixing enhancement between two streams. With the increase of shock wave strength, the thickness and mixing efficiency both increase in the shock–mixing layer. When the incident position of the shock wave moves upstream, the thickness of the shock–mixing layer increases much more and the mixing is realized faster. The present conclusions are helpful to further propose flow control strategy for mixing enhancement of supersonic flows.