CFD Simulations and Analyses for Bridge-Scour Development Using a Dynamic-Mesh Updating Technique

A computational fluid dynamics (CFD)-based simulation methodology using a dynamic mesh updating technique is proposed in this study. This method can numerically describe the complicated 3D scour behavior around the piers of bridges. By redeveloping a commercial CFD computer program, the transient shear stress in a k-εturbulence model is first calculated, where the shear stress is regarded as a key parameter to judge the sediment incipient motion in scour process. Then, the dynamic mesh updating technique is implemented to assure a practical and accurate scour simulation by individually updating the finite element (FE) model nodes of the riverbed in each time step. A good calculation convergence is further ensured by controlling the stability during the equation solving process, in simple terms by avoiding the denominator (or generalized denominator) being close to zero. Second, based on the comparisons between the numerical results and experimental measurements, it is confirmed that the proposed numerical modeling method successfully predicts the flow field and scour (riverbed) profile. Finally, through a parametric case study the influence of the pier types on the scour behaviors is investigated by the proposed simulation. It is also proven that the proposed simulation method is a good and reliable tool to predict and discuss the spatial development of bridge scour process.