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Hydro-morphodynamic model with immersed boundary method for local scour at bridge piers

ABSTRACT Bridge pier scour was simulated by a coupled fully 3D hydro-morphodynamic model and validated against 24 experimental datasets for a combination of different pier shapes, approach velocities and sediment bed material. The proposed numerical model adopts an Eulerian multi-fluid model to account for rolling and saltating particles and computes bed shear stresses from implicit wall functions. ANSYS Fluent solved the continuity and Navier-Stokes equations, closed by the RSM turbulence model, which were coupled with sediment transport submodels by source terms. Numerical instabilities were addressed in the sediment transport submodels which were ascribed to the fine mesh resolution required to resolve the crucial horseshoe vortex and the diffusion resulting from the discretization of the Immersed Boundary method.