Turbulence Measurements in a Compressible Reattaching Shear Layer

Detailed hot-wire measurements of the longitudinal component of the mass-flow fluctuations have been made in an approximately self-preserving free shear layer reattaching on a 20-deg ramp at Mach number 2.9. The experimental configuration is especially designed to provide a well-defined initial condition for the reattachment process. The absolute mass-flow turbulence intensity increases dramatically through the compression in the reattachment region, which is in sharp contrast to similar subsonic reattachments. It is clear that the mean dilatation contributes significantly to the turbulence amplification. In addition, the length scale is affected strongly by the presence of extra strain rates. Prediction of this flow will require some sophisticated modeling, and the challenge to the predictor is clear.