Two-way coupled large eddy simulation for non-equilibrium suspended sediment transport

Non-equilibrium suspended sediment transport in coastal engineering is characterized by complex interactions among turbulent flows, seabed topography, and structures. This study developed a two-way coupled large eddy simulation suspended sediment transport model sedTransFoam based on the open-source OpenFOAM framework. The solver comprehensively accounts for turbulence modulation caused by high-concentration sediment and interactions between sediment. Additionally, it incorporates a flux boundary condition based on turbulent burst theory to accurately simulate instantaneous sediment transport characteristics under strong turbulence effects. The sloped terrain and pile group structure generate complex turbulence-sediment interactions, making them a classic setting for studying non-equilibrium suspended sediment transport. The solver is employed to investigate sediment dynamics, where sloped terrain and pile groups generate complex turbulence and sediment transport patterns. The simulations demonstrate that the sloped terrain induces large-scale Kelvin–Helmholtz vortices, which drive erosion through enhanced shear stress. Pile groups shift vortices toward interfaces, where shear stress and turbulent kinetic energy primarily govern sediment transport. Transverse momentum exchange is predominantly driven by turbulent mixing (accounting for approximately 75%), while high-density pile configurations increase siltation due to reduced turbulence scales.