Stabilization of a mach 6 boundary layer using a two-dimensional cavity

The stability of a hypersonic boundary layer over a flat plate to wall blowing-suction with the effect of a two-dimensional cavity at different locations is investigated using direct numerical simulations. The results indicate that the second mode is damped when the cavity is placed closely downstream of the synchronization point of mode F and mode S, whereas the effect is reversed if it is located upstream and further downstream of the synchronization point. Strong damping of the disturbances is observed inside the cavity, which is found to be consistent with the thermoacoustic interpretation. It is suggested that an efficient way to stabilize the boundary layer dominated by the second-mode instabilities is to put a local cavity in the close downstream region of the synchronization point corresponding to the most dangerous frequency.