The vortex-induced vibration of a circular cylinder with helical grooves

Abstract

A novel approach utilizing helical grooves is proposed to suppress the vortex-induced vibration of a circular cylinder. Initially, the influence of the depth, width and pitch of the helical grooves on the aerodynamic coefficients of a stationary rigid circular cylinder is numerically investigated at $\mathrm{Re}\approx 6.8\times 10^4$, where $\mathrm{Re}$ denotes the Reynolds number based on the cylinder diameter and the incoming flow velocity. Owing to the disturbance of the helical grooves, the spanwise convection in the wake is enhanced and the spanwise correlations of the pressure and vortices are reduced, so that the alternate shedding of vortices in the wake is suppressed. Therefore, the aerodynamic coefficients on the cylinder are reduced. With the optimal parameters, the average drag coefficient, $C{d}_{mean}$, is reduced by more than 33%, and the root-mean-square value of the lift coefficient, $C{l}_{rms}$, is decreased by over 92%. For a spring-mounted cylinder with one-degree-of-freedom vibrations, the helical grooves can maximally reduce the amplitude of the VIV of a cylinder by up to 94.4%, Additionally, they can completely eliminate the frequency lock-in phenomenon. Then, the stable negative aerodynamic stiffness and damping cannot be maintained, thereby effectively suppressing the VIV.