A partial cell technique for modeling the morphological change and scour

A novel partial cell technique applied on structured grids is developed to track the deformation of water-soil interface associated with beach morphological change and toe scour in front of coastal structures. It allows the use of the same orthogonal structured grids for morphological, sediment transport and hydrodynamic models therefore, has the advantage of consuming less CPU and without the need to adapt grids to the evolving beach morphology. An improved sand-slide model with better mass conservation is introduced to resolve the avalanche behaviour of the sediment motion. The RANS-VOF hydrodynamic model has been extended to cope with complex bathymetry. The newly developed numerical model suite, coupling the RANS-VOF model, a bedload sediment transport model and a morphological model using the partial cell technique, are validated against the analytical solutions and laboratory measurements for different incoming wave conditions, local water depths and bottom slopes. This study reveals the key processes that govern the behaviour of beach morphology change in front of a vertical coastal structure during storms. The model-data comparisons demonstrate the robustness of partial cell technique to capture the movement of the water-soil interface.