Numerical Analysis on Suppression of Vortex Induced Vibration of a Square Cylinder with Control Rods

Vortex-induced vibration (VIV) and galloping of bluff bodies pose significant challenges in offshore, civil, and mechanical engineering applications, often leading to severe structural fatigue and failure. This study numerically investigates the suppression of VIV in a square cylinder using downstream control rods of two distinct geometries—circular and square—placed at a gap spacing of 0.5D, where D is the characteristic length of the cylinder, and oriented at 45° to the main cylinder axis. Simulations were performed at Reynolds numbers of 100 and 210 using the finite volume method (FVM) in ANSYS Fluent, with structural motion modeled through a spring–mass system implemented via a user-defined function (UDF). Our results demonstrate that control rods significantly modify wake dynamics by elongating and thickening shear layers, enhancing vorticity diffusion, and enlarging recirculation regions. At Re = 100, square control rods fully suppressed VIV, while circular rods reduced oscillations by approximately 99%. In the galloping regime (Re = 210), vibration amplitudes were reduced by ~97% with circular rods and ~99.9% with square rods. Square rods consistently provided stronger suppression by stabilizing the near-wake and accelerating vorticity dissipation. These findings highlight the crucial influence of control rod geometry in passive vibration mitigation and provide practical insights for designing robust suppression strategies.