Numerical investigation of sand sliding methods for hydro-morphodynamic modelling

In numerical modelling of scour around riverine and coastal structures using a hydro-morphodynamic model, a discrete sand sliding procedure needs to be implemented to avoid the occurrence of unrealistic bed profiles. In this study, two commonly employed sand sliding techniques, namely, the artificial transport rate method (ATRM) and the geometry-based method (GBM), are implemented in OpenFOAM and their performances are evaluated for five three-dimensional test cases. The test cases are classified into cases with and without sediment transport induced by a flow field. In the first three test cases, in the absence of a flow field, sand heap avalanches for different geometries and bed boundary grid structures are modelled to compare the methods in terms of simulation time and mass continuity. In test cases 4 and 5, in the presence of a flow field, the sensitivity of the sand sliding methods coupled with a hydro-morphodynamic model to different bed mesh structures is evaluated in modelling scour. The results of the analysis demonstrate that modelling of the sand sliding procedure using ATRM requires higher computational time, while its results are highly independent of the bed mesh structure with lower mass continuity error, <0.2% in all test cases, in comparison with GBM.