Supersonic Cavity-Based Flow Control Using a Quasi-DC Discharge

Abstract

The Quasi-DC (Q-DC) discharge is studied as an active flow control authority on a rear-facing cavity in a supersonic duct by creating an oblique shockwave that impinges the cavity. This geometry simulates the geometry of a typical scramjet flameholding scheme. The tests were performed at the University of Notre Dame in the SBR-50 supersonic blowdown rig with dried air at M=2. Schlieren imaging is used to view the flow field with and without the Q-DC discharge in operation. A significant change in the flow field structure is observed. Pressure sensors detect a pressure increase throughout the entire rear-facing cavity while the Q-DC discharge is operating. This reveals that the cavity redistributes the pressure increase from the shockwave as a result of the flow within the cavity being subsonic. As a result of this pressure absorption and redistribution, the impinging shockwave created by the Q-DC is almost completely absorbed. This absorption is confirmed by the schlieren images. The data reveal that the discharge power is the dominating influence, as compared to electrode/discharge geometry, on the pressure increase produced in the cavity. There is a nearly linear correlation between the power of the discharge and the pressure increase produced directly behind the discharge, in the cavity, and on the ramp of the cavity (to varying magnitudes). It is suggested that the 11 electrode system may be slightly more effective than the 7 electrode system.