Control of Compression-Ramp-Induced Interaction with Steady Microjets

An experimental investigation was conducted to control an interaction induced by a 24 dcg compression ramp in a Mach 2 flow. An array of steady microjets of six different configurations is placed 6.86 upstream of the interaction. The primary objective was to study the effect of jet-to-jet spacing and the variation in pitch and skew angles in controlling 1) the extent of separation and 2) the amplitude of shock unsteadiness in the intermittent region of separation. The results show that a jet-to-jet spacing of 13d is most effective in controlling the extent of separation and the depth of the corrugations in the separation line despite a significant reduction in the momentum flux ratio compared to the closely spaced jet configurations. Skewing an already 45 deg pitched jet to 135 deg results in a further reduction in the overall extent of separation at all control pressures. Although a significant reduction in the separation-shock unsteadiness was observed for the 90 deg pitched and skewed jets at P-oj = 208 kPa, the 135 deg skewed (and 45 deg pitched) jets show a further reduction in this value, but at P-oj = 180 kPa, much lower than the frcestream total pressure. The separation-shock spectra show a shift in the characteristic frequency from 0.35 kHz for no control to 0.7 kHz for 135 deg skewed jets (for the highest P-oj tested), which is a direct indication of an overall reduction in the separation bubble size.