Direct numerical Simulations of instability-wave generation and propagation in supersonic boundary layers

Stringent requirements for component performance plus economic and environmental challenges for supersonic aircraft leave little room for inefficiencies in airframe design [1], making it necessary to have accurate and reliable prediction tools for boundary-layer transition to turbulence. To help develop and calibrate such tools, direct numerical simulations (DNS) of various stages during transition over both model and realistic flow configurations are necessary. This paper describes the application of a DNS solver based on high-order compact differences to supersonic swept-wing configurations. Specifically, spatial simulations of crossflow instability in swept-wing boundary layers have been performed and validated against predictions based on the simpler but nearly equally accurate parabolized stability equations. The excitation of crossflow modes due to localized surface disturbances is also investigated. To help increase the efficiency of crossflow simulations for infinite-span swept wings, a simple modification to the DNS procedure is shown to significantly reduce the total grid requirement.