Velocity measurements of compressible, turbulent mixing layers

An experimental investigation of compressible, turbulent mixing layers has been conducted using pressure measurements, schlieren photographs and velocity measurements with a two-component laser Doppler velocimeter system. Seven mixing layer cases were examined, with relative Mach numbers ranging from 0.40 to 1.97, which spans the region of significant compressibility effects. The spatial development and similarity of the mixing layers were examined, as well as the entrainment process and the effects of panicle dynamics. An analysis to determine the entrainment mass fraction of a fully developed, compressible mixing layer is also presented. The development of the mixing layers required a Reynolds number (based on the freestream velocity difference and local mixing layer thickness) on the order of 10⁵. In the fully developed regions of the mixing layers, it was found that transverse turbulence intensities and normalized kinematic Reynolds stresses decreased with increasing relative Mach number, while the streamwise turbulence intensities and kinematic Reynolds stress correlation coefficients remained constant.