Generation and Control of Oblique Shocks Using Microjets

Jets in a supersonic crossflow are known to produce a three-dimensional bow-shock structure due to the blockage of the flow. In the present study, streamwise linear arrays of high-momentum microjets are used to generate either single or multiple oblique shocks in a supersonic crossflow. The shocks generated using microjets can be tailored in terms of their strength and be made either parallel or coalescing, depending on the application. Flow visualization using shadowgraph and density field measurements using background-oriented schlieren (BOS) technique were carried out for a range of microjet operating conditions. The results obtained using the two methods are consistent and complementary and show a linear variation of oblique shock angles with a microjet pressure ratio over the range of conditions tested. The density field obtained using BOS clearly shows the oblique shocks generated using these microjet arrays, the jump in density across the shock, the extent of the high-density field, the expansion fan, and the associated decrease in density. The results suggest that microjet arrays can be successfully used to develop techniques for sonic boom mitigation and high-performance supersonic inlets.