Effect of a streamwise vortex on supersonic boundary layer transition

Abstract

Supersonic boundary layer transition induced by a streamwise vortex is experimentally investigated based on the nanoparticle-based planar laser scattering technology, with an inflow Mach number of 2.7 and a unit Reynolds number of 8.79 × 106 m−1. Though the vortex is outside the boundary layer, it results in obvious difference of transition position along spanwise direction. On the up-wash side, transition to turbulence is completed in advance compared to the vortex-free case, and transition position moves more upstream as the vortex approaches the wall. Conversely, the transition process on down-wash side is inhibited. The promotion and inhibition effects on transition are found to be induced by the influence of vortex on streak density.