Numerical Study of Crossflow Jet Generated Instabilities in a High-Speed Boundary Layer

Numerical simulations of 3-D disturbances induced by an underexpanded jet in supersonic crossflow (JISC) in the Mach 5.4 flat-plate boundary layer (BL) are carried out. The Navier–Stokes equations for compressible perfect gas are integrated using the in-house solver implementing an implicit finite-volume shock-capturing scheme with the second-order approximation in space and time. The numerical solutions indicate that the wall normal injection through a circular hole forms an underexpanded jet of barrel shape, which induces a system of vortices propagating downstream. These vortices are destabilized at a short distance that leads to rapid nonlinear breakdown and formation of a turbulent wedge. The vortex structure, its instability and breakdown to turbulence resemble those induced by an isolated roughness element. It is shown that the normal wall injection effectively trips the BL flow. This encourages further numerical studies of active tripping of high-speed BL flows using rows of JISC.