Effect of three-dimensional smooth humps on hypersonic boundary layer instability of streamwise vortices over a yawed cone

Abstract

This paper describes the design of a class of three-dimensional (3D) smooth humps mounted on a yawed cone model for a high-precision compressible Navier–Stokes solver. The influence of isolated 3D humps with different heights on the linear stability of streamwise vortices over a yawed cone with a 7° half-angle at a 6° angle-of-attack, free-stream Mach number of 6, and unit Reynolds number of 1.0×107/m is investigated. The results show that smooth humps induce stationary streaks inside the streamwise vortices over a yawed cone, effectively increasing the energy of the inward vortex and inhibiting the evolution and development of the outward vortex. Stability analysis shows that the induced streaks enhance the inner mode instability, suppress the outer mode instability, and reduce the dominant frequency of the outer mode. The stability properties of the hump-induced streaks are studied, and the physical process of the transformation between the new streak instability mode and the original boundary layer mode is revealed. The eN method based on global stability theory is used to predict the transition location along the centerline on the leeward side of the cone. It is found that configurations with hump heights of 0.153 and 0.267 times the local boundary layer thickness result in a transition delay of ∼3% and ∼11%, respectively.