Combined effect of bridge piers and floodplain vegetation on main channel hydraulics

Abstract

Different complex flow fields like down-flow, horseshoe vortex, wake vortices and bow waves are generated due to the interaction of approach flow with bridge piers. Scientific researches around bridge piers with floodplain vegetation presents the multilevel fluid dynamics. This allows understanding the interactions of bridge pier and heterogeneous vegetation cover on the river corridor with the flow field of a stream channel. The present study experimentally investigated a three-dimensional turbulent flow field in the main channel of the river with the combined effect of bridge pier and floodplain vegetation. Further, the presence of a single large diameter pier with floodplain vegetation increases the main channel velocity up to 36% compared to no-obstruction on the floodplain. For the same case, the length of the vortex is more, and its strength is two times more than the double pier of smaller diameter. This reveals that the secondary vortex grows its size and strength in the large diameter pier. Furthermore, the convergence induced contraction of the curved channel along with the bridge pier on its floodplain solely affects the turbulent structures in the mainstream of the channel. The experiments associated with the pier diameter and number of piers placed on the floodplain will be notable in understanding flow behavior. In addition, for river ecosystem restoration, the notion of pier diameter, number of piers, and floodplain vegetation should be included in the design practice.