Investigation of vortex-induced vibrations of rotating cylinders with different surface roughnesses

The vortex-induced vibrations of a two-degree-of-freedom rough rotating cylinder at a low Reynolds number of 200 and a mass ratio of 2.6 are investigated via numerical simulations. The relevant calculation parameters are as follows: a rotation rate between zero and one, surface roughness height between 0% and 15%, and reduced velocity between 1 and 12. It is found that reasonable rough surface and rotational motion of the smooth cylinder are two effective factors for suppressing the vortex-induced vibration (VIV) response. Conversely, a rotating cylinder with a rough surface enhances the VIV response. Four wake patterns (2S, P + S, 2P, and multiple vortices patterns) are captured. At low rotation rates, with increasing roughness height, the wake pattern develops into a multiple vortex pattern after multiple evolutions. The variation in roughness at a high rotation rate does not correlate with a change in the wake pattern. The area of the cylindrical motion trajectory is positively correlated with the roughness height, and the time-averaged dimensionless displacements of the cross-flow and in-line flow directions increase with increasing roughness height.