3D SPH simulation of dynamic water surface and its interaction with underlying flow structure for turbulent open channel flows over rough beds

In this study, a fully 3D numerical model based on the Smoothed Particle Hydrodynamics (SPH) approach has been developed to simulate turbulent open channel flows over a fixed rough bed. The model focuses on the study of dynamic free surface behavior as well as its interaction with underlying flow structures near the rough bed. The model is improved from the open source code SPHysics (http://www.sphysics.org) by adding more advanced turbulence and rough bed treatment schemes. A modified sub-particle-scale (SPS) eddy viscosity model is proposed to reflect the turbulence transfer mechanisms and a modified drag force equation is included into the momentum equations to account for the existence of roughness elements on the bed as well as on the sidewalls. The computed results of various free surface patterns have been compared with the laboratory measurements of the fluctuating water surface elevations in the streamwise and spanwise directions of a rectangular open-channel flow under a range of flow conditions. The comparison has demonstrated that the proposed 3D SPH model can simulate well the complex free surface flows over a fixed rough bed.