A numerical study on the flow-induced vibrations of flexible cylinders attached with fixed short fairings

Fairings have been used to suppress the vortex-induced vibrations(VIV) of deep water cylinders in the offshore and marine engineering applications. When properly functioning, they can reduce both the cylinder oscillation amplitude in the cross-flow direction and the fluid drag force in the in-line direction. Plenty research reports can be found on the rigid cylinder VIV suppression performances of fairings while very few research work discuss their VIV suppression performances on flexible cylinders. In the present work, a self-developed high-resolution fluid–structure interaction code based on the computational fluid dynamics is used to simulate the flexible cylinder responses attached with differently covered fixed short fairings. The Reynolds number based on the incoming velocity and the bluff body diameter is 1.68×104. The short fairings are found not to induce strong galloping oscillations in the flexible cylinders while the galloping is prominent in the rigid cylinder cases at large reduced velocities. The different short fairing setups are found to influence the local fluid–structure energy transport distributions and the travelling wave directions in the flexible cylinder responses, which eventually influences the flexible cylinder oscillation amplitude distributions, response frequencies and mode orders. •Flow-induced vibrations of flexible cylinders with fixed fairings are numerically studied.•Rigid short fairings can reduce mean deflection with no obvious increment in vibration amplitudes.•Fatigue damage can be reduced under proper fairing setup.•Fairings change travelling wave characters which influence response amplitudes and frequencies.•Vortex shedding modes in flexible cylinder cases are in agreement with rigid cylinder forced vibration data.