Development of an enhanced implicit DEM and coupled ISPH-DEM solver for landslide tsunami simulations

This study focuses on the establishment of an enhanced implicit DEM (Discrete Element Method) sediment model and its coupling with a refined ISPH (Incompressible Smoothed Particle Hydrodynamics) fluid model, resulting in an ISPH-DEM solver, for simulating landslide tsunami scenarios. The previously developed fully implicit DEM by the authors has been further refined through the incorporation of a second-order time advancement scheme (trapezoidal rule) and an internal iterative loop approach, yielding a more mathematically rigorous full-implicit formulation of DEM. This enhanced implicit DEM is subsequently coupled with an enhanced ISPH with incorporation of both the correction scheme for apparent fluid particle volume and the resistance force term into the momentum equations. The proposed ISPH-DEM solver employs an implicit algorithm in both fluid and sediment models, enabling consistent time coupling using identical time step intervals in both phases. The proposed implicit DEM is first validated through benchmark tests of single particle bounce on a horizontal plane, single particle rolling on an inclined slope, and granular column collapse composed of multiple particles. Following the validation of the proposed DEM, the integrated fully implicit ISPH-DEM solver is applied to test cases of landslide tsunamis.