Effect of wall temperature on the stability of hypersonic boundary layer over a blunt wedge under the action of pulse wave in incoming stream

A high-order accurate finite difference method is employed for direct numerical simulation of hypersonic unsteady flow over a blunt wedge with slow acoustic wave disturbance in incoming stream. The differences of disturbance modal development in boundary layer between pulse wave and continuous wave are compared, and the effects of wall temperature on the development of disturbance mode in hypersonic boundary layer are mainly discussed. The results show that fundamental frequency mode is the strongest disturbance in the nose tip hypersonic boundary layer for both pulse wave and continuous wave. The growth of unstable mode in boundary layer under the action of pulse wave is much smaller than that under the action of continuous wave for both fundamental frequency and harmonic frequency. For pulse wave, all disturbance mode degenerates along the flow direction within a nose radius; while in the region far from the nose the dominant mode shifts to high frequency. The development of different mode varies each other. In general terms, from upstream to downstream, the high frequency components increase quickly and low frequency components almost are restrained to grow. The results also show that wall temperature has less influence on fundamental frequency, while the development of high frequency mode is affected significantly. Cooling the wall accelerates the development of high frequency, and inhibits the degeneration of low frequency mode along the streamwise.