On the Effects of Transverse-Jet Injection into a Supersonic Shear Layer

This paper reports on observations in supersonic flow experiments conducted in an expansion-turn geometry, augmented by inclined-jet injection, in the Supersonic Shear Layer (S^3L) facility at Caltech. The experiments, designed to exploit hydrodynamic instabilities in compressible shear layers, were conducted in a non-reacting environment and at moderate compressibility. A shear layer is formed between a supersonic upper stream (M_1=1.5) and a subsonic lower stream (U_R=8.5 m/s) injected at an angle α = 30° with respect to the horizontal. The coupling of streamwise vortices generated by 5 jets inclined at 30° with respect to the free-stream and the shear layer was investigated. The Color schlieren images illustrate some of the phenomenology associated with transverse-jet injection and shear-layer interaction, and characterize the jet influence on shear-layer entrainment. A substantial increase of the shear layer thickness compared to the unperturbed case (without transverse jets) is reported for a jet-to-freestream momentum flux ratio, q̄, of 2