Experimental Investigation of Gas Injection into the Boundary Layer on a Slender Body in Supersonic Flow

A method for injection of gas into the boundary layer on a slender body in supersonic flow while minimizing perturbation to the mean flow is examined experimentally. Injection of gas is equivalent to a sudden increase in the displacement thickness of the boundary layer, which produces an oblique shock that propagates into the inviscid region of the flow. It is found that modification of the geometry of the body can compensate for the increased displacement thickness created by injection and minimize the production of oblique waves. However, the resulting near-wall injection layer is observed to be unstable and a turbulent boundary layer develops downstream of the injection region. The instability of the flow is examined using velocity profiles from a compressible Navier-Stokes computation. In-depth analysis of the mean flow and stability are performed by Fedorov in a companion paper