Component decomposition and spatial distribution of unsteady forces on a circular cylinder oscillated under various amplitudes at Re = 2.0×104

Abstract

Vortex-induced vibrations (VIVs) are of practical significance in the design of engineering structures, and the dynamic loads responsible for VIVs are thus crucial. In this study, the force characteristics of a circular cylinder undergoing forced oscillations at vortex lock-in states are investigated by employing three-dimensional large eddy simulations (LES) at a moderate subcritical Reynolds number of 2.0 × 104. Simulations of the oscillating cylinder are performed under a series of normalized amplitudes ranging from 0.05 to 0.60 at a fixed reduced velocity of 6.0. Moreover, a force spectrum-based approach is proposed to decompose the overall force into motion-induced and vortex-shedding components. Alternative insights into the spatial distribution of the force are also obtained by analysing the spanwise correlation, pressure field, and flow feature. The numerical results show that the motion-induced lifts experience an abrupt jump in both magnitude and phase as the oscillation amplitude increases. Furthermore, the motion-induced forces are almost fully correlated except in the phase-jump regime, although the correlation of the overall forces is relatively weak. Finally, the identified force parameters are successfully applied to predict the VIV amplitudes of the cylinder under various mass-damping conditions.