Investigation of two patterns of vortex-induced vibration in a 5:1 rectangular section under different parameters

In this study, a 5:1 rectangular section was taken as the research object. An aerodynamic reduced-order model was used to verify whether the rectangular section had a similar oscillation mechanism to a circular section based on the results of two-dimensional unsteady Reynolds-averaged Navier–Stokes calculations. Computational fluid dynamics was used to study the vertical oscillation characteristics of the 5:1 rectangular section under the influence of different parameters. The results showed that the vertical oscillation of the rectangular section could be divided into two patterns according to the oscillation characteristics: “resonance-induced vibration” and “competition-induced vibration.” The resonance-induced vibration shows a quick development in amplitude, while competition-induced vibration has two stages before stabilization. The vibration amplitude, oscillation frequency, and lock-in region were affected by variations in the mass ratio. The damping ratio had less effect on the oscillation frequency and vibration amplitude than the mass ratio. However, a reduction in the damping ratio enlarged the lock-in region at a high reduced velocity. Additionally, the difference in the initial displacement had a considerable influence on the vibration amplitude of competition-induced vibration, while it had little effect on resonance-induced vibration.