Time-Resolved Digital Interferometry for High Speed Flow Visualization in Hypersonic Shock Tunnel

In this article we report on the development of time-resolved digital interferometric visualization technique integrated with short duration (1 ms) hypersonic shock tunnel. Dynamics of the Mach 6 flow field around 40 degrees blunt cone model is visualized using a combination of cw laser, Mach-Zehnder interferometer and a very high-speed digital camera. Digital interferograms with time resolution of 139 mu s were recorded during 1 ms test time of our HST4 facility. Measured time-resolved evolution of shock structure around the model is compared with Schlieren technique and CFD simulation results to validate the proposed technique. Infinite fringe interferograms are evaluated using active contour technique and Fourier transform fringe analysis to extract density data of the hypersonic flow field around the model. Estimated time-resolved density. data show the variation in the density within shock layer.