Vortex-induced vibrations of a rectangular cylinder

Abstract

Vortex-induced vibrations (VIV) of an elastically mounted rectangular cylinder with one degree of freedom immersed into viscous incompressible uniform flows have been researched via the lattice Boltzmann method. The Reynolds number is fixed at 100, the mechanical damping is set to zero and the reduced velocity is varied between 1 and 16. Results demonstrate that both side ratio and mass ratio have significant influences on the behaviours of fluids and structures. Resonance can be excited extensively and its region extends with decreasing side ratio and mass ratio. In the region of low side ratio and mass ratio, a phenomenon of vibration frequency shift usually happens and even though the structure leaves the resonance region, the cylinder still undergoes a large-amplitude oscillation. A total of three distinct vortex wake modes are observed. Mechanistic analysis indicates that the shift of oscillation frequency is induced by the competition between wake mode and structure mode and large-amplitude vibrations in the resonance region will be caused by the power transfer between fluids and structures. The excitation of wake mode is associated with the cylinder shape and response amplitude. Meanwhile, the process of vortex formation has significant influences on the cylinder motion.