Vortex-induced vibration suppression of cactus-like cylinders

This study experimentally investigated the suppression effect and mechanism of vortex-induced vibration (VIV) of cactus-like cylinders with eight ridges in the Reynolds number range of 8733-29,533. The results indicate that the bionic cross-section models can effectively reduce the cross-flow (CF) displacement amplitude and the in-line (IL) mean displacement of VIV while advancing the reduced velocity (Ur) range of VIV. When the current flows towards the ridges, the vibration frequency is greater than the natural frequency, analogous to the coupling of VIV and galloping, but galloping does not occur after leaving the VIV range. The peak values of displacement, lift coefficient, and drag coefficient decreased by 57.96%, 11.35%, and 23.76%, respectively. The frequency ratio and turbulent kinetic energy increase are responsible for the ineffective suppression of the models' lift and drag coefficients. The flow field distribution and vortex shedding mode are drastically altered by the model's backflow side ridges. When the current flows towards the grooves, the Ur range of VIV does not decrease, and the frequency ratio does not increase significantly. The peak values of displacement, lift coefficient, and drag coefficient are reduced by 32.15%, 42.51%, and 33.28%, respectively.