Scale Interactions in Compressible Turbulent Mixing Layers.

The interactions between the large and small scales of turbulence in compressible turbulent mixing layers are investigated by means of direct numerical simulation of the compressible Navier–Stokes equations. Two typical cases with the convective Mach numbers Mc = 0.3 and 1.6 are considered to reveal the influence of compressibility on the scale interactions. The velocity signals are decomposed into large-scale and small-scale ones based on the Taylor length scale for the analysis of scale interactions and split into solenoidal and compressive parts for the investigation of compressibility effect. It is found that the small scales are modulated by the large-scale velocity fluctuations with different properties on both sides of the mixing layer, and the large-scale modulation on the small scales is reduced with increase in the convective Mach number. The interaction between the large-scale compressive velocity fluctuations and the small scales is mainly associated with absolute values of the large-scale compressive velocity fluctuations and is independent of transverse position of the mixing layer. The large-scale compressive velocity fluctuations increase with the solenoidal counterparts. [ABSTRACT FROM AUTHOR]