Prediction of flow around a sharp-nosed bridge pier: influence of the Froude number and free-surface variation on the flow field

Abstract

This study investigates the influence of free-surface variation on the velocity field using numerical simulations of flow around a sharp-nosed pier that is representative of a typical masonry bridge pier. The study evaluates the assumption that free-surface effects are negligible at small Froude numbers by comparing the change in flow field predictions due to the use of a free-surface model (i.e. multi-phase simulation with a volume of fluid (VOF) model in place of a rigid-lid approximation (i.e. single phase simulation). Results show that simulations using the VOF model are in better agreement with experimental data than those using the rigid-lid approximation. Importantly, results show that even though the change in free-surface height near the pier is small comparative to the approach flow, it still has a significant effect on velocities in front of the pier and in the wake region, and including at low Froude numbers.