Experimental investigation on cavity noise reduction with surface dielectric barrier discharge plasma actuator

Cavity oscillation is a significant and challenging issue in aerospace engineering. Surface dielectric barrier discharge (SDBD) plasma actuators can induce electrical body forces instantaneously in the flow, and have been proven to be effective in suppressing the noise caused by cavity oscillation. This research focuses on the steady and unsteady operation modes of SDBD plasma actuators. A systematic parametric study of the cavity flow is conducted experimentally, and the flow characteristics are analyzed through acoustic and particle image velocimetry measurements. Results indicate that under steady control, increased peak-to-peak voltage enhances control effectiveness, and the reduction of wall-normal velocity fluctuation within the shear layer is the primary cause of noise suppression. Under unsteady control, the effects of dimensionless modulation frequency St_m are analyzed in detail. The alteration of vortex evolution patterns leads to two distinct flow regimes, with St_m = 1.6 as the dividing line. When St_m < 1.6, only the frequency information related to plasma actuation is observed in the sound pressure spectrum. Although the peak sound pressure level (SPL) increases, the overall SPL decreases owing to the narrow bandwidth at the peak frequency. When St_m > 1.6, the frequency information of the original flow is also retained. The case of St_m = 2.4 achieves optimal noise suppression, employing the same control mechanism as steady actuation.