Characteristics and suppression of flow-induced vibrations of two circular cylinders in tandem arrangement (1st report, characteristics of flow-induced vibrations in cross-flow vibration)

This study investigated the characteristics of flow-induced vibrations of two circular cylinders in tandem arrangement. The response characteristics on elastically supported two circular cylinders were examined by a free vibration test in this study. Also, the behavior of the shear layers separated from the two circular cylinders was investigated on the basis of the visualized flow patterns. The measurements were performed by changing the spacing ratio L/D (L is the gap spacing between two circular cylinders, D is the diameter of cylinder). The main findings were that (i) the response characteristics of flow-induced vibrations were classified into five patterns in the region of L/D ≦3.2, (ii) the flow-induced vibrations of the two cylinders depended strongly on the fluctuating lift forces of the two cylidners, (iii) the phase difference between the response of the two cylinders was proportional to distance between two cylinders, (iv) there were two kinds of vibration patterns at critical spacing of L/D=0.6 and 2.7, and (v) there exsisted the hysteresis phenomenon on two cylinders caused by acceleration and deceleration of the free-stream velocity.