Numerical investigation on VIV of a circular cylinder with multiple small control rods

This study conducts a numerical simulation of the two-degree-of-freedom vortex-induced vibration (VIV) for a circular cylinder attached to multiple small control rods. It systematically investigates the effects of control rod number n, attack angle alpha, and gap ratio G/D on the vibration responses of the main cylinder. The control rod arrangements are classified into symmetric and asymmetric configurations based on the attack angle variation. The 5, 7, and 9 small control rods present similar impacts on the VIV's characteristics of the circular cylinder. The VIV of the main cylinder is significantly suppressed by the odd number of small control rods in two regions. The 1st excellent VIV suppression (EVS) region locates in the gap ratio of G/D=(0.2, 0.3) for all attack angles. The 2nd EVS region is within a wide range of gap ratios at the 2nd symmetric configuration. The nine control rods at G/D = 1.4-1.5 in the 2nd EVS region can completely suppress the circular cylinder VIV. Meanwhile, the flow structure of the cylinder group is fully symmetric, and vortex shedding cannot be formed behind any circular cylinders.