Experimental study on response performance of vortex-induced vibration on a flexible cylinder

Laboratory tests were conducted on a flexible cylinder to improve the understanding of the response performance of vortex-induced vibration (VIV). The experiment was performed in a towing tank and the relative current was simulated by towing the flexible cylinder in one direction. Based on modal superposition, VIV displacements were obtained from the measured strain. VIV responses from different current cases were analysed, and the response performances, such as the motion trajectory, strain response, and fatigue damage, were studied. The motion trajectory for the flexible cylinder at low velocity displays the typical type-eight figure, very similar to that for a rigid cylinder. However, with increased velocity, the motion trajectory becomes chaotic, induced by the multi-mode VIV responses. Simplified fatigue damage based on the typical steady motion trajectory is usually a little larger than the measured fatigue damage based on the chaotic motion trajectory, but of the same order.