Standard PIV system using double-pulse laser and double frame camera with high resolution is used to be applied to for high-speed flow. Nowadays PIV system (high-speed camera and high repetition double pulse laser) with 1k × 1k pixels in image size and 2kHz in frame rate is available. This system is called as "Dynamic PIV", and the dynamic range for time in this Dynamic PIV system is expanded 1 to 2000. It can acquire the time serial images of transient of high-speed flow. In this paper, we describe multi-scale PIV system with two camera systems and its signal control of cameras and a laser. This multi-scale PIV system is validated by artificial images using simulation data of vortex flows and is applied to experiment with free jet flow. We indicate this system can expand the dynamic range for space.

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The flow in a supersonic wind tunnel was visualized by using a computational fluid dynamics (CFD) analysis. The flow was expressed as virtual Schlieren optical image based on the air density gradient in the CFD analysis. In this study, the optimization result of supersonic wind tunnel nozzle contour by using the optimization method which was developed previously was taken as an example, the improvement of the flow quality by the optimization was checked by the visualization. As the result, the small pressure waves generated in the flow could be detected and the change in the distribution of these pressure waves with the optimization was seen by using this visualization.

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