Passive Control of the Aero-Optics of a Supersonic Shear Layer

When a planar wavefront passes through a compressible shear layer, density gradients lead to the refraction and warping of the wavefront. Particularly in the presence of density fluctuations, this phenomenon can be a hindrance to the preservation of the wavefront. In this study, we measure the shear layer created through boundary-layer separation on a backward-facing step within a Mach 2.8 freestream. Within the first phase of this study, measurements are obtained using stereoscopic particle image velocimetry (SPIV) to quantify the incoming boundary layer upstream of separation along with the shear layer itself. Quantities of interest include the boundary layer thickness, the shear layer thickness, and Reynolds stresses. With these data, passive flow control devices can be properly sized, with planned experiments including wavefront measurements to quantify the aero-optic health of the shear layer.