流れ方向強制振動並列二円柱からの渦放出(同径の場合)(流体工学,流体機械)

概要

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In this study, the flow features of vortex shedding from a pair of parallel arranged circular cylinders oscillating along the direction of the flow were observed by visualizing water flow experiment at the ranges of the frequency ratio f/f_K=0〜7, amplitude ratio 2a/d=0.125, 0.25, 0.5 and 0.75, gap ratio G/d=0.25, 0.75 and 1.75, and Reynolds numbers Re=470〜670 (towing water tank test) and 700〜750 (closed circuit water channel test). The variations of mean vortex shedding frequency from each oscillating cylinder were investigated. As a result of the experiments, typical flow patterns of lock-in state or un-lock-in state were shown every gap ratio G/d. Although the cylinder oscillation frequency f is lower than the natural Karman vortex's frequency f_K, the lock-in phenomenon can be seen. It was found that the measurement result depended on the observation point because the rearrangement of vortex formation had changed the characteristics of the flow. When the cylinders were oscillated to the direction of flow, the flow pattern of bias gap flow became not seen. The map of lock-in state in the lock-in range was obtained. It was found that the lock-in range and the lock-in form were more different from the case of single oscillating cylinder.
2008-12-25