Experimental investigation on the vortex-induced vibration of a flexible pipe conveying gas flow with the presence of small-hole gas leakage

This paper reports the experimental results of the vortex-induced vibration (VIV) of a flexible submarine pipe conveying gas flow with the presence of small-hole gas leakage from its mid-span. The tests were conducted in a recirculation water flume in the reduced velocity range of U-r = 1.16-10.65 using the non-intrusive measurement, corresponding to the Reynolds number range of Re = 133-1218. The vibration characteristics of the pipe span with an aspect ratio of 95 in the cases of four leakage orientations (theta) and three conveyed gas flow rates (Q) are examined as well as the gas diffusion to reveal the interaction between the VIV and gas leakage. The experimental results indicate that the presence of gas leakage enhances the VIV, accompanied by the reduction in the onset U-r for vibration. The gas diffusion behavior is related to the pipe vibration as well as the incoming flow velocity. In particular, the gas bubble coalescence is observed in the wake in small U-r cases when the leakage rate is relatively large. Furthermore, as U-r increases, the discharged gas bubbles migrate in clusters, suggesting a noticeable correlation with the pipe vibration cycle. In the considered U-r range, five gas diffusion modes are identified based on the amount of gas bubbles, the occurrence of bubble coalescence and the correlation with pipe vibration, and the partition of diffusion modes is provided in the Q-U-r and theta-U(r )maps.