Moving Shock Impinging to Cylinder Normal to Wall
Asai et al. (2001) demonstrated the feasibility of Ru(dpp) AA-PSP for time – resolved unsteady pressure measurements in the NAL 0.44 m Hypersonic Shock Tunnel. Figure 9.39 is a schematic of the experimental setup for the shock tube tests. A circular block of a 12 mm diameter was installed vertically in the center of a PSP-coated part flush mounted on the shock tube wall. Calibration of PSP was made by adjusting the test section pressure prior to running the shock tube. Full-field measurements were acquired using a CCD camera with an intensifier that can be gated at successive instants after incidence of a moving shock wave. Illumination for PSP was provided by a flash lamp. Sequential images were obtained from 475 to 530 |J. s in an interval of 5 |J. s. The camera gating time was set at 10 |j. s. Figure 9.40 shows a time sequence of images of an unsteady pressure field induced by a moving shock wave interacting with the stationary circular block, where the shock speed was 610 m/s. Because the observation window flush mounted on the surface of the tube acted like a 2D concave lens, the images were compressed vertically so that a circular section of the cylinder looked like an ellipse. As shown in Fig. 9.40, a curved high-pressure region induced by the reflected shock was formed in the front of the block after the incident plane shock impinged to the block. At the same time, a part of the incident shock continued traveling downstream after it was deflected, and the expansion waves were generated. A pair of symmetric vortices, which are visualized as the low-pressure regions in Fig. 9.40, formed and grew behind the circular block.