The experimental investigation of the water jet flow issuing from the circular pipe with the fluttering fins is addressed. Especially, the effects of the fluttering fins on the jet diffusion were studied. The measurements of the flow visualization were performed by the system, which was composed of the dual-pulse Nd:YAG-laser, the CCD-camera and the high speed camera. By analyzing the velocity distributions obtained from PIV, the jet widths with or without the fluttering fins were compared. It has been clarified that the jet diffusion is enhanced due to the influence of the fluttering fins. Furthermore, the continuous wavelet transform and the wavelet multi-resolution analysis were respectively applied to analyzing the fluctuating velocity and the image information obtained in the section normal to the jet flow, and the flow structures were decomposed into wavelet components of various scales. It has been found that the flow structures of the jet flow with the fluttering fins are different from that without them.
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