Effects of cavitation on vortex-induced vibration of a flexible circular cylinder simulated by fluid-structure interaction method

To investigate the effects of the cavitation on the vortex-induced vibration, the flow and the vibration characteristics of a flexible circular cylinder in the non-cavitating and cavitating flows at Re = 200 are simulated using a fluid-structure interaction (FSI) solver, developed in the OpenFOAM framework. The accuracy of the fluid-structure interaction solver is verified using the benchmark cases. For a freely vibrating circular cylinder, the characteristics of the vortex-induced vibration are determined at different frequency ratios. The frequency lock-in is observed in both the cavitating flow and the non-cavitating flow, and the lock-in frequency range is larger in the cavitating flow with a smaller vibration amplitude. In the lock-in frequency range, due to the reduction of the fluid forces and the resonance effects at the dominant frequency, the vibration amplitude is decreased in the cavitating flow, as compared to the non-cavitating flow. Moreover, the low-density vapor and the cavitation collapse weaken the constraints of the flow and the stability of the shedding vortices, respectively, making the flow around the circular cylinder more sensitive to the structural vibration. Consequently, the lock-in frequency range is larger in the cavitating flow.