Shockwave/Boundary-Layer Interaction Control on a Compression Ramp Using Steady Microjets

An experimental investigation was conducted to control the amplitude of shock unsteadiness associated with a 24 deg compression-ramp-induced interaction in a Mach 2 flow. Two control configurations in the form of an array of 1) 16 90-deg-pitched steady micro-air-jet vortex-generating devices (AJVG1), and 2) eight pairs of 45-deg-pitched steady micro-air-jet vortex-generating devices (AJVG2) were studied. Each AJVG device was placed upstream of the interaction region at 12.5 delta from the compression corner. Both micro-AJVG configurations show a reduction in separation shock strength and help considerably reduce the height of the lambda-wave triple point with increase in P-oj. Pitching the rnicrojets at 45 deg, as in the AJVG2 configuration, prevents a stronger control-generated bow shock to form ahead of the injectors and, hence, reduces the obstruction component of the interaction significantly. A well-defined separation line for no control is seen to get replaced by a highly corrugated separation line with control. Significant reduction (up to 67%) in the peak rms value is observed in the intermittent region of separation with AJVG1 for P-oj >= 208.5 k Pa while the same is achieved with AJVG2 at a much higher P-oj (>500 kPa). The spectral content of the pressure fluctuations also indicate that, relative to the AJVG2 configuration, AJVG1 is successful in reducing the amplitude of fluctuations in the range of unsteadiness by an order of magnitude as soon as P-oj exceeds 208.5 kPa. The amplitude of these fluctuations is seen to further decrease with increase in P-oj.