Development of Combined Asymptotic and Numerical Procedures for Transonic and Hypersonic Flows.

Hypersonic and transonic flows of practical interest were investigated using combined asymptotic and numerical methods. In the hypersonic regime, strong, moderate and weak interaction between shock and boundary layers were emphasized in relation to stability and transition. A new instability was identified in which disturbances reflect from the boundary layer edge of a waveguide formed by the boundary layer and a flat plate. Other new amplification phenomena were discovered related to three-dimensional disturbances and finite amplitude fluctuations in thin Newtonian shock layers. It was shown that the latter can produce inflectional instabilities that can be exploited to enhance mixing in scramjet combustors. Similitudes were used to collapse Reentry-F cone data to a universal curve, forming a basis for quick-response hypersonic transition prediction. Another theoretical analysis showed that ultrasonically absorptive thermal protection surfaces can damp inviscid second-mode acoustic instabilities with the possibility of transition control. In the transonic speed range, an area rule for wall interference was developed as well as asymptotic theories for lifting interference and the effect of non circular walls. These provide systematic approximation procedures for quick correction methods and optimal model sizing for maximum unit Reynolds number and minimum wall interference.