Shock / boundary-layer interaction control using three-dimensional bumps in supersonic engine inlets

The effects of three dimensional bump control on separated shock-wave / boundarylayer interactions have been investigated experimentally at M _∞ = 1.5, aiming to reduce total pressure losses incurred by strong normal shock / boundary-layer interactions. Such a situation occurs, for example, inside mixed-compression supersonic engine inlets or on external-compression inlets. Various bump configurations have been tested and their effects have been evaluated in various aspects such as total pressure recovery and boundary-layer thickness. Without control, the normal shock caused a region of relatively two-dimensional separation. Three-dimensional bumps commonly broke up this separation into individual regions of attached and separated flow, giving an overall reduction of the magnitude of separation. Fairly two-dimensional λ-shock structures and streamwise vortex pairs have been observed in all tested configurations. A configuration comprising multiple long, high, narrow rounded bumps has demonstrated the best performance, producing an appreciable total pressure saving as much as 30% owing to a λ-shock benefit with minimum viscous penalty from localised separation.