Micro-Ramp Control for Shock Train Structure and Oscillation

Abstract

Micro-ramps for shock train control were investigated experimentally in a Mach 1.85 supersonic isolator flow using three device heights. A mechanical flap was mounted downstream and linearly choked, forcing the shock train to travel upstream of the micro-ramp from the exit. Wall static pressure measurements along the primary and corner regions obtained a more complete pressure distribution. Detailed structures of the shock train were recorded using schlieren visualization with circular, horizontal, vertical, and color knife edges. The results show that the wake and wave structures generated by the micro-ramp control the shock train. The taller the device, the stronger the wake and wave structures, and the greater the control. The wake and wave structures shorten or eliminate the Mach stem in the shock train leading edge, causing modification of shocks downstream from pseudonormal to oblique, inhibiting the thickening of the boundary layer that results from shock impingement, slowing down the contraction of the supersonic core flow, and allowing more high total pressure fluid to develop downstream. The wake structure was found to promote the oscillation and upstream motion of the shock train. The wave structure can restrain shock train oscillation and upstream propagation of the downstream adverse pressure gradient, enhancing the resistance backpressure of the flowfield downstream of the micro-ramp.