Experimental investigations of cavity-actuated supersonic oscillating jet

Wind tunnel tests were conducted at different back pressures in a vacuum-type wind tunnel for a novel supersonic fluidic oscillator which consists of a two-dimensional Laval nozzle and two face to face cavities, to obtain its characteristics and the conditions for jet oscillating. The experimental results show that periodic flipping of the supersonic jet appears from NPR = 3.4 to 5.6 according to schlieren visualization and fluctuating pressures. The cross-junction mode for estimating the resonance frequency in a pipe with two closed side branches was modified and obtained comparable estimations of the frequency of jet flipping with experimental data. The coupling of the modified cross-junction mode and the Rossiter mode for cavity resonance could be the reason for the flipping of the supersonic jets. Compared to free jet, the oscillating jet achieves significant mixing enhancement based on the analysis of jet axial peak velocity and the entrainment.