Flow dynamics through a submerged bridge opening with overtopping

Abstract

ABSTRACTThis paper reports the results of detailed numerical simulations of the flow over a submerged bridge. The method of Large Eddy Simulation (LES) is applied, which allows elucidation of the instantaneous flow and accurate quantification of its turbulence statistics. The in-house LES code employs a free surface algorithm based on the Level Set Method (LSM) to determine the complex water surface profile over the bridge, which is validated with data from a physical model of the bridge under analogous flow conditions. Numerically predicted water surface profiles show good agreement with measured data. The water surface resembles that of the flow over a broad-crested weir with a plunging nappe and a standing wave downstream of the bridge. The mean flow is characterized by a multitude of complex flow features including horizontal recirculation zones upstream and downstream of the bridge abutment and vertical recirculation zones of the separated plunging flow. The latter influences significantly the near-bed turbulence and the bed shear stress.