Effect of rounded corners on flow-induced vibration of a square cylinder at a low Reynolds number of 200

Abstract

Flow-induced vibration of a square cylinder with rounded corners at a low Reynolds number of 200 is investigated numerically. Simulations are conducted for a mass ratio of 10, a damping ratio of 0 and non-dimensional radius (R) of the rounded corners ranging from 0 (square cylinder) to 0.5 (circular cylinder). The principal aim of this study is to find out the effects of the rounded corner on vortex-induced vibration and galloping, which are typical phenomena of an elastically mounted square cylinder in fluid flow. Galloping is fully suppressed if R is greater than 0.1 inclusive, and greatly mitigated as R = 0.03 and 0.05 and still exists with large amplitude if R = 0.01. However, the rounded corner is found to broaden the VIV lock-in regime and also increases the maximum response amplitude in the lock-in regime. The maximum non-dimensional amplitude in the lock-in regime increases from 0.26 to 0.57 as R increases from 0 to 0.5. Rounded corner also affects the beating phenomenon in the VIV lock-in regime. The beating is type A beating when R is small and type B beating when R is large. In type A beating, the vibration frequency varies around the natural frequency, while in type B beating, the vibration frequency varies between the vortex shedding frequency and natural frequency. In the galloping regime both the vibration displacement and the lift coefficient have dual frequencies: a low vibration frequency and a high vortex shedding frequency. The dominant frequency of the lift coefficient is the vortex shedding frequency instead of the vibration frequency.