CFD simulation of local scouring around airfoil-shaped bridge piers with and without collar

Abstract

In this paper, the effectiveness of airfoil-shaped pier with and without a collar on local scour depth reduction is numerically investigated utilizing FLOW-3D model. The results show that on a constant T* = VT/D (V: velocity, T: time, D: pier width), increasing the width of the ballet of pier would result on the reduction of maximum scour depth and it would mitigate the scouring depth behind the piers. Also, because of lack of uplift vortices in using airfoil-shaped pier, there would be no scouring behind the piers. Utilizing collar on the airfoil-shaped pier would result in a reduction of maximum scouring depth in front of the pier as well and the uplift vortices behind the pier would reduce. Investigation of orientation discipline of the airfoil-shaped pier on flow route shows that the pier which is reversely placed in the flow direction (the keen part in front), will cause the horseshoe vortex to weaken and make the scouring to start from downstream. However, scouring caused by horseshoe vortex in front of the airfoil-shaped pier is strongly more than scouring caused by wake vortex in the rear of the pier.