Flow-induced vibration of a circular cylinder with splitter plates placed upstream and downstream individually and simultaneously

Flow-induced vibration (FIV) of a circular cylinder with splitter plates placed upstream and downstream individually and simultaneously at a low Reynolds number of 120 is numerically investigated using the direct numerical simulation (DNS). The effects of the downstream plate length and the arrangement of plates on the hydrodynamic forces, vibration response and flow wake are examined. The numerical results reveal that a downstream plate alleviates the vortex-induced vibration (VIV) at U-r <= 9 (U-r is the reduced velocity) while exciting the galloping at U-r>9. The reattachment of shear layers on the plate surface generates an extra lift force, contributing to the galloping. The longer the plate, the larger the onset reduced velocity of galloping, which is associated with the jump of vibration amplitude and lift fluctuation as well as the fall of frequencies of vibration and vortex shedding. With the introduction of an upstream plate, the boundary layers develop along the plate before attaching on the cylinder surface, while the vortex shedding is delayed and flow wake is narrowed as compared to the bare cylinder, contributing to the VIV suppression. The galloping excited by the rear plate is eliminated by simultaneously placing an upstream plate, and the best suppression of VIV is achieved by the bilateral plates due to the more streamlined profile.