The parameters of instability wave of supersonic mixing layer(Mc=0.5,M1=3.5/M2=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 Mc,2
YANG WuBingZHUANG FengGanSHEN QingGUAN FaMingWANG QiangYI ShiHeZHAO YuXinHE LinTIAN LiFeng
The existing methods for measuring aero-optical aberration suffer from several problems,such as low spatiotemporal resolution,sensitivity to environment,and integral effects.A new method for measuring aero-optical aberration of supersonic flow is proposed.Based on the self-developed measuring method of supersonic density field,the wavefront aberration induced by a cross-section of supersonic flow field could be measured by ray-tracing.Compared with other methods,the present one has three significant innovations:(1) high spatiotemporal resolution.Its time resolution is 6 ns,and the spatial resolution can reach up to micrometers;(2) it can avoid the integral effects and study the wavefront aberration induced by the flow field of interest locally;(3) it can also avoid the influence from the test section wall boundary layers and environmental disturbances.The present method was applied to supersonic flow around an optical bow cap.The results of high spatiotemporal resolution reveal fine wavefront structures,and show that shock waves,expansion waves and turbulent boundary layers have different impacts on the wavefront aberration.
