Experimental and numerical study on instability structure of the supersonic mixing layer (M _c = 0.5)

The parameters of instability wave of supersonic mixing layer (M _c =0.5, M ₁=3.5/M ₂=1.4) are measured by flow visualization and calculated by means of two-dimensional direct numerical simulaitons of the compressible Navier-Stokes equations. In both cases of the mixing layer with harmonic disturbance or not, the comparative results indicate that the wavelength of the two-dimensional wave is equal to the vortex spacing in the streamwise direction because the difference between them is less than 1%. However, the measured convective velocity of the large-scale structure deviates from the theoretical isentropic prediction about 10%. Here the measured value confirms that M _c,2<M _c,1 for the supersonic-supersonic mixing layer. Furthermore, the pairing and intermittent phenomenon are recorded clearly by flow visualization.