Simulation of floating debris in SPH shallow water flow model with tsunami application

Many post-tsunami field investigations affirm that the large floating debris transported by the flow contributes significantly to the destruction of on-land buildings. However, few simulation tools have been developed to predict the debris behaviour under violent flow conditions involving complex debris-fluid, debris-debris, debris-bed surface and debris-wall (solid structure) interactions. This paper introduces a fully coupled model of three-dimensional (3-D) debris motion in shallow-water flow. The model uses Smoothed Particle Hydrodynamics (SPH) to solve the shallow-water equations (SWEs) and represents debris motion using the modified Morison equation. The Discrete Element Method (DEM) model is used for the collision mechanism. The flow model is formulated based on the Euler-Lagrange equations that provide the vertical component of velocity and can therefore be coupled with the 3-D debris motion. A new solid boundary condition for shallow flows is introduced. The open boundary condition is used for wave generation by imposing inflow and outflow in predetermined zones. The SPH solves the wet-dry interface automatically. The model is implemented in an open-source software DualSPHysics. SWE-SPH flow model is initially validated against experimental data, followed by the debris model compared with an analytical solution and physical experiments, which gives close agreement. This model is expected to be a robust tool for predicting the hazards caused by extreme floodings, such as tsunamis.