Numerical investigations of the round-nosed bridge pier length effects on the bed shear stress

Local scour around bridge piers is a complex phenomenon that threatens the river bridges safety. In this paper, we have studied the influence of the aerodynamic shape of the bridge pier on the bed shear stress, and we have carried out a parametric study considering the length of the aerodynamic shape that better reduces the bed shear stress. For that purpose, a number of simulations have been carried out using a finite volume method (FVM) and for the turbulence model, we have chosen the detached eddy simulation (DES) for it's capability to capture the rich dynamics of the horseshoe vortex at the upstream junction between the pier and the bed. The present parametric study shows that the aerodynamic shape of the bridge pier strongly affects the flow pattern around it; also, the result reveals that, with a constant width, the length of the best round nosed pier shape must not exceed 2.5 the width. Beyond that, the bridge pier length does not have any effects on the bed shear stress.