Artificial resistance of Eulerian-Lagrangian method in 3D numerical model

The artificial resistance of the Eulerian-Lagrangian Method (ELM) in a 3D hydrodynamic model is observed and characterized by a rising free-surface elevation when the time step decreases. The phenomenon is illustrated and investigated by combining the numerical experiments and the formal analysis. The analysis indicates that the abnormality results from the linear interpolation of the ELM which does not match the nonlinear distribution of the velocity. Based on the analysis, the phenomena are explained. Moreover, the computations by a 3D hydrodynamic model using the sigma-coordinate indicate that the artificial resistance of the ELM is universal, but the grid which follows the topography and free surface better will alleviate its negative influence.