Coastal sediment transport simulation by smoothed particle hydrodynamics

The coastal sediment transport is very important for the planning and design for shore protection and coastal structures. And it is a challenge for coastal engineers and scientists due to its complicated features including the wave breaking, turbulence and mixing, fluid-sediment interaction and flow-topography coupling. This study is to present a nearshore hydrodynamics, sediment transport and morphological model by Smoothed Particle Hydrodynamics (SPH) Method, especially in the surf zone. The hydrodynamics model provides the necessary information and driving force for the sediment transport and morphological model. The SPH hydro-dynamics model solves the Navier-Stokes equations including the sub-particle scheme for the Large-Eddy Simulation. The sediment transport is modeled as concentration equation by solving convection-diffusion equation. The morphological model is based on the sand mass conservation. The SPH hydrodynamics is validated by the wave flume experiments about the breaking waves on plane beach. The results show satisfactory agreement with the experiment data and its capability to simulate the complicated physics pretty well due to its Lagrangian method which includes the nonlinear convective term without efforts. An upwind SPH numerical scheme is proposed to solve the settling term in convection-diffusion equation in the sediment suspension model. And the numerical experiment shows the standard SPH scheme has the numerical diffusion and dispersion problem. The sediment suspension model is tested by the experiments for oscillatory flow above the ripples, which the convective motion dominates the process and play an important mechanism for the sediment suspension and distribution. The comparisons indicate the model can predict sediment concentration under the wave condition fairly well. The morphological model is applied in the flat bed case and verified by mass conservation. It needs further research for practical application. Finally the three SPH models is used to study the wave breaking, sediment transport and the resulting beach evolution under the different wave conditions. Expensive computation is the disadvantage of SPH method. The parallel algorithm in the SPH model is also discussed in the last. The parallel algorithm has very good efficiency by using buffer communication and load balancing techniques