Abstract: Wind tunnel experiments are carried out to control a ramp induced shock wave/turbulent boundary layer interaction with high-frequency microsecond pulse discharge in a Mach 2.5 supersonic flow. The discharge is generated between 6 pairs of electrodes arranged in the streamwise direction upstream of the ramp, and the discharge frequency f=14 kHz is adopted, which is close to the characteristic frequency of the incoming boundary layer. High-speed schlieren imaging technology is used to record the dynamic flows. The recorded schlieren images are statistically processed by average, root-mean-square, proper orthogonal decomposition, dynamic mode decomposition, and Fourier transform methods based on their spatial gray values, and the unsteady characteristics of the shock wave/turbulent boundary layer interaction with and without control are compared and studied. The results show that for the baseline flow without control, the low-frequency characteristics are shown as the oscillation of the separation shock, as well as the shedding behavior of the large-scale eddies in the boundary layer flowing across the shock, and the middle and high-frequency characteristics are shown as the interaction between the small-scale eddies in the boundary layer and the shock. For the flow with control, the incoming boundary layer actuated by the discharge has eddies with an increased scale, which are interacting with the separation shock. As a result, the oscillation of the shock turns into the pulsation of multiple compression waves, the boundary layer flowing through the shock pulses more strongly, and the low-frequency oscillation(10-300 Hz) of the separation shock is alleviated. In this case, the low-frequency characteristic of the flow is mainly manifested as the shedding behaviors of the large-scale eddies in the boundary layer flowing across the shock, while the middle and high-frequency characteristics of the flow are still manifested as the vortex-wave interactions as those in the baseline flow.

Key words: plasma flow control, shock wave/boundary layer interaction, unsteady flow, turbulent flow, supersonic aircraft