Mixing enhancement of transverse jets in supersonic crossflow using an actively controlled novel fluidic oscillator

This study investigates the fluid dynamics and mixing characteristics of an oscillating sonic jet injected into a supersonic cross flow of Mach 2.1 using experimental and computational techniques. The oscillating jet is produced by a novel fluidic oscillator, which consists of a primary rectangular duct that expands into an outer duct with sudden expansion. Control jets are injected in the lateral direction from the side walls of the sudden expansion in an out-of-phase manner to oscillate the injected jet in the spanwise direction of the crossflow. Experimental and numerical investigations based on wall static pressure and mass fraction fluctuations, respectively, revealed that the injected jet oscillation frequency matches the control jet frequency. The iso-surface of lambda-2 criterion showed the presence of various dominant vortex structures, such as counter-rotating vortex pairs, horseshoe vortex, sidewall vortices, and trailing vortices. Helicity contour plots showed that the streamwise vortices oscillate in the spanwise direction with the control strategy and promote the spread of the injected jet in the spanwise direction. The spatiotemporal reconstruction (z–t plot) of the density gradients at a particular streamwise location revealed that the bow shock produced by the interaction of the injected jet and the crossflow oscillates with the actuation of the control strategy. The power spectral density of the z–t plot revealed that the shock wave oscillation frequency matches the control jet frequency. The oscillating jet produced by the control strategy showed significant mixing enhancement in supersonic crossflow compared to a simple rectangular injection.