Unstart of a Supersonic Model Inlet/Isolator Flow Induced by Mass Injection

*A transverse jet is injected into a supersonic model inlet/isolator flow to induce unstart. Planar Laser Rayleigh Scattering (PLRS) from condensed CO2 particles is used to visualize the unsteady flow during unstart. Pressure traces are recorded using high speed pressure sensors located in the bottom wall of the tunnel. A series of time sequence PLRS images reveals that an unstart shock originates near the jet injection nozzle and propagates upstream, unstarting the inlet flow upon its arrival at the inlet lip. Studies conducted over a range of model configurations indicate that the presence of turbulent wall boundary layers strongly affect the unstart dynamics. It is found that relatively thick turbulent boundary layers in asymmetric wall boundary layer configurations prompt the formation of unstart shocks whereas symmetric boundary layer conditions lead to the formation of pseudoshocks. Both cases facilitate fast inlet unstart when compared to cases in which there are initially relatively thin laminar boundary layers.