OBSERVATIONS OF LIQUID JETS INJECTED INTO A HIGHLY ACCELERATED SUPERSONIC BOUNDARY-LAYER

Experiments were conducted to observe the cross-sectional structure an d streamwise growth of round transverse liquid jets injected into a hi ghly accelerated boundary layer in supersonic flow. The accompanying s hock structure was also visualized. In one case, a round jet of aceton e was injected into a fully turbulent Mach 2.5 boundary layer that was subsequently accelerated and partially laminarized through a sharp Pr andtl-Meyer expansion corner. In the second case, a jet was injected i nto the laminarized Mach 3.2 boundary layer downstream of the expansio n corner at the same jet-to-freestream momentum ratio. The jet and sho ck structure in both cases were visualized using schlieren optics. Wal l-flow patterns were visualized using paints. It was found that the la teral spreading of jets injected downstream of the expansion fan was a ugmented close to the wall and had a cross-sectional structure signifi cantly different from that of the jet injected upstream: the upstream jet spreads rapidly at the expansion corner in both the lateral and ve rtical directions.