Normal shock/boundary-layer interaction control using aeroelastic mesotlaps

A normal shock/boundary-layer interaction control technique termed mesoflaps for aeroelastic recirculating transpiration has been investigated in a planar Mach 1.37 wind tunnel. In this flow-control system, an array of small flaps is mounted over a cavity; the flaps deflect aeroelastically under the pressure loads imposed by the normal shock, thereby allowing recirculation from downstream of the shock to upstream. Qualitative analysis of the mesoflap control was investigated with spark shadowgraph visualizations and oil-streak surface-flow visualizations, whereas quantitative analysis was achieved by measuring surface pressure distributions and boundary-layer velocity profiles. Nine different mesoflap arrays were investigated, in addition to the solid-wall reference case. It was found that flap thickness and, therefore, transpiration rate, had a demonstrable effect on static and total pressure recovery, in addition to boundary-layer integral properties. Although some of the arrays did not provide a performance benefit, one particular flap array was found to have significantly higher static and total pressure recoveries than the solid-wall reference case, while simultaneously demonstrating a reduction in boundary-layer momentum thickness and unchanged displacement thickness.