Construction works located in a fluvial and maritime environment, during their lifetime, the hydromechanical and physicochemical variabilities, as well as climate change, contribute to their possible deterioration. Take bridge piers or offshore wind turbine foundations (monopile foundation, suction monopod foundation, ...) are some examples. Among the resulting phenomena, local scouring has been identified as one of the main factors. In the United States, over the last 30 years, a thousand bridges failed are associated to scour and erosion. Therefore, the understanding of this process plays an important role in predicting scour to design foundations and protection solutions.

Despite of numerous experimental and/or numerical researches in the literature, not all physical processes involved are yet well understood and presented. Among these studies, the appearance and the formation of horseshoe vortex in front of the circular pile, the formation of the vortex shedding behind and the generation of turbulence impact to the mechanism of sediment transportation around the structure foundations were investigated. This process is very complex due to in most cases it involves two-phase turbulent flows and various sediment transport modes.

Classical sediment transport models are based on empirical formula for the bed-load and suspended-load governed by Exner equation. In large scale, bed level change in computational fluid dynamics (CFD) needs to be interpolated from computational morphodynamics. Over the last decade, the modeling of sediment transport using two-phase flows are developed at the intermediate scale. This approach is based on the solution of momentum and mass conservation equations for each phase, water and sediment. The sediment shear stress is modeled using a frictional rheology of granular media.

This paper aims at presenting a CFD-DEM (Discrete Elements Method) coupling that takes into account the particle-particle collisions and the solid-fluid interactions at the local granular scale. The different models of drag force and the pressure forces exerted on the particles are integrated. The DEM-CFD coupling is validated with experimental sedimentation for one particle reported in the literature review. Finally, the results of scour around a circular pile and its validation will be presented.