Response of an oblique shock train to downstream periodic pressure perturbations

An experimental investigation of the response of an oblique shock train to downstream periodic pressure perturbations was conducted. The oblique shock train is generated in a Mach 2.7 ducted flow and controlled by a downstream elliptical shaft. Cyclic rotating of the shaft leads to a periodic oscillatory motion of the oblique shock train. Six cases of perturbation frequency are studied. The results indicate that the downstream pressure perturbations propagate upstream to cause the oblique shock train to oscillate with a translational motion back and forth and the wall pressure to fluctuate with the same frequency. There is no distinct relative motion between the first oblique shock and the second shock during the motion process of the oblique shock train. The entire oblique shock train exhibits its behaviour of rigid motion and the strength of the first oblique shock of the oblique shock train is nearly stable during its periodic motion. There is a clear hysteresis effect in that the oblique shock train travels along a different path for the upstream and downstream motions. A simple analytical model was built based on these experimental data to analyse the oblique shock train dynamics.