Numerical simulation of turbulent spots generated by unstable wave packets in a hypersonic boundary layer

The generation of a turbulent spot by an unstable wave packet propagating in a Mach-6 flat-plate boundary layer is considered. The asymptotic shape of the wave packet is obtained in the far field from the excitation point using linear stability theory. Unsteady boundary conditions are formulated for direct numerical simulation. They allow for excitation of a well-developed wave packet with specified amplitude, skipping the linear growth stage. Robustness of these boundary conditions for modeling of the nonlinear breakdown of unstable wave packets into turbulent spots is examined.