Research On The Unsteady Flow Physics Of Oblique Shock Train

The shock wave usually appears when a supersonic flow decelerates and the accompanying pressure is on the increase. While the oblique shock is strong enough to separate the boundary lauer on a wall surface in internal compressible flows, one or more reflected shocks appear downstream of the original oblique shock. A multiple oblique shock/boundary-layer intersection thus formed, called " oblique shock train". The unsteady flow physics of the oblique train strongly affects the performance and efficiency of various flow devices of a flight vehicle. Unsteady oblique shock trains in a duct were characterized with Mach 5 upstream flow and varying backpressure conditions. A time-history schlieren technique, accompanied by simultaneous dynamic pressure measurements, was performed to understand the transient behavior of oblique shock trains. Typical flow field is numerical simulated to understand the mechanism of the dynamic behavior of oblique shock trains. A database showing time-resolved schileren images with corresponding transient pressure profile was constructed. Investigation on the oblique shock train dynamics revealed the oscillatory nature of the shock train during upstream propagation. The oblique shock train forward propagation process is not a stable motion process. It contains two kind motion modes: rapidly forward and steadily forward. The unsteady numerical results show the phenomenon of separation merger is observed when the motion in the shock train propagation process is rapidly forward. Additional research is in progress to understand the oblique shock train propagation behavior with the downstream pressure disturbance. The simple theoretical model in this paper makes qualitative predictions of shock dynamics in cases without significant separated flow region.