Supersonic cavity shear layer control using spanwise pulsed spark discharge array

An experimental study on supersonic cavity flow control using a spanwise pulsed spark discharge array (SP-PSDA) is performed in this paper. High-speed schlieren imaging at a frame rate of 50 kHz is deployed for flow visualization. The schlieren snapshots, as well as their statistics, are analyzed to reveal the supersonic cavity flow control effect and its underlying mechanism. Results show that the shear layer presents a wave-like oscillation due to thermal bulbs induced by SP-PSDA. Specifically, the shear layer structure in the baseline case resembles an incomplete hairpin structure, which becomes complete after plasma actuation. SP-PSDA actuation at 5 kHz has a better control effect, which enhances the IRMS of the whole hairpin structure and produces several channels within it - these aid momentum transport within the shear layer. According to the results of proper orthogonal decomposition, the thermal bulbs couple with the shear layer to form large-scale coherent structures. These structures excite the Kelvin-Helmholtz instability, converting the oscillation frequency of the shear layer to an actuation frequency.