Experimental study on mitigating vortex-induced vibration of a bridge by using passive vortex generators

It has been reported that three-dimensional spanwise-varying control is very efficient in suppressing vortex shedding behind bluff bodies. Therefore, a new passive control method, spanwise-varying passive vortex generator (PVG), was proposed to mitigate the vortex-induced-vibration (VIV) of a bridge. The PVGs can directly generate stream-wise vortices, which behave like secondary wake instability modes (3D instability modes). Therefore, the PVGs can cause 3D instability of spanwise vortex shedding and suppress VIV. In this study, isolated PVGs were arranged on the lower surface of the bridge in spanwise direction, and their control effects on mitigating VIV were investigated through wind tunnel tests. The results show that as PVGs are arranged with spanwise distance of 1-3H (H is the height of the bridge) and the PVG height is 0.1-0.25H, both vertical and torsional VIV can be completely suppressed, and the trailing edge is the key region to suppress VIV. Further, the control effects of PVG are barely influenced by the boundary layer of the bridge. The spectrum analysis of the wake velocity shows that the PVG can completely suppress the vortex shedding near a wake, and thereby resulting in the vanishing of VIV.