Numerical simulation of local scour around bridge piers using novel inlet turbulent boundary conditions

Abstract

The numerical results of local scour for bridge piers are significantly affected by the inlet turbulent boundary conditions. A novel self-sustaining model (SSM) and corresponding the new inlet turbulent boundary conditions are proposed to quickly obtain a stable flow field of horizontal homogeneity. The Reynolds averaged Navier-Stokes (RANS) equations, and standard k-ԑ turbulence model are employed to solve the complex flow around the bridge piers. Based on the sediment transport model considering the effect of the arbitrary slope of riverbed and the collapse of sediment, the dynamic evolution process of local scouring around bridge piers is simulated. Then, the applicability of the numerical approach for local scour around bridge pier is validated by the flume test comparing with the flow pattern, the maximum scour depth and the morphology of scour pit. Finally, the influence factors of local scour for bridge piers including common pier shapes and different angle of attack are studied. The numerical results indicate that the proposed SSM can develop homogeneous isotropic turbulence to fine simulate local scour with prescribed inlet turbulent boundary conditions. The established sediment collapse model can reasonably reflect the collapse process in scouring. Importantly, the proposed numerical methods can provide a reasonable prediction of maximum scour depth. In addition, the performances of the local scouring are greatly sensitive to the pier shape and the angle of attack. The inflow parallelling to piers or choosing appropriate pier shape helpful to ease the scour.