Stabilization of controlled disturbances in a supersonic boundary layer by slots

A pioneering study of the influence of streamwise slots (grooves) of various depths h (corresponding to the Reynolds numbers Reh = 900 and 1300) on the stability of a supersonic (Mach number M = 2) boundary layer on a flat plate with respect to controlled disturbances of the first (vorticity) mode of instability determining the laminar-turbulent transition at M = 2 is performed. At Reynolds numbers Reh = 900 and 1300, the growth rates of three-dimensional disturbances at frequency f = 14 kHz are found to be smaller than the corresponding value for the smooth plate. Thus, it is shown that controlled disturbances of the first mode can be stabilized by streamwise aligned slots of a small depth (Reh < 1500).