Wavelet Analysis Local Long Shallow Cavity Effect on Second Mode in Hypersonic Boundary Layer

The second mode stability of a hypersonic boundary layer over a flat plate with the effect of a long shallow cavity investigated by spatial direct numerical simulation. Unsteady disturbance is introduced by a slot of periodic suction-blowing at the plate leading edge. The results indicate the stabilization effect is influenced by the frequency of the second mode. For all the cases studied, the cavity is located in the close downstream region of the synchronization point corresponding to the most dangerous frequency. The cavity can reduce the amplitude of pressure signals. The energy distribution is similar in different streamwise position. In normal direction, with the height increases, the energy distribution becomes dispersion at high frequency band. The cavity has no significant effect on the energy distribution.