This paper is concerned with the water circular jet flow issuing along a circular cylinder and in the longitudinal direction of it. In particular, attention is focused on the flow aspect in the cross section normal to the jet flow. The flow visualization in the several cross sections has been carried out by means of the system composed of the dual-pulse YAG-laser, the CCD-camera, and the CRV unit. The image information has been processed by a PIV method. The wavelet analysis has been also conducted by using the velocity component in the spanwise direction obtained from the image processing. As a result, the interesting flow aspect obtained from the velocity contour maps in the previous experiment has been explained by using the image processing results. Furthermore, it has been clarified that at the downstream location far from the exit of a circular pipe the jet issues with swinging from side to side largely and its frequency is relatively low.

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