Supersonic Cavity Flow Control Using a Spanwise Array of Leading-Edge Tabs

Abstract

Motivated by the successful application of active control using segmented spanwise blowing, this work investigates passive flow control for a rectangular cavity in supersonic flow using a spanwise array of leading-edge tabs to reduce unsteady pressure loads on the cavity surface. The cavity studied here has a length-to-depth ratio of 6 and width-to-depth ratio of 6 with a turbulent boundary layer at the leading edge and a freestream Mach number of 1.4. Fluctuating surface pressure measurements within the cavity show that the leading-edge tabs have similar effectiveness as leading-edge blowing of the same spanwise wavelength in reducing pressure fluctuations on the cavity surfaces. Streamwise-aligned particle image velocimetry (PIV) measurements show evidence of deflection of the shear layer at the cavity opening and modification of recirculation characteristics associated with the controlled flow. Furthermore, cross-stream stereoscopic PIV measurements reveal counter-rotating streamwise vortices, which persist throughout the cavity length. Proper orthogonal decomposition modes of cross-stream-aligned PIV measurements show that leading-edge tabs are successful in breaking up the flow into smaller-scale modes. Surface flow visualization of the cavity floor and aft wall show differences in the recirculation patterns for the baseline and controlled flows. The present analysis provides insights on how the passive tabs effectively control high-speed cavity flow and demonstrates that the control mechanisms are analogous to steady leading-edge blowing strategies.