A Moving Particle Semi-implicit Numerical Method for Modelling Sediment Dynamic

Fluvial/coastal sediment transport, debris flows, and landslides are a few examples of sediment dynamic problems. Modelling and predicting the mechanical behaviours of these so-called multiphase granular flows are crucial for optimum engineering designs and hazard management. The mesh-free particle approaches, with an inherent ability to deal with highly-dynamic multiphase systems, are becoming the powerful tools for such predictions. This research paper aims to develop and evaluate an improved mesh-free particle model, based on a multiphase Weakly Compressible Moving Particle Semi-implicit (WC-MPS) method to model a gravity-driven sediment dynamic problem in subaerial and subaquatic conditions. Several stability improvement techniques are adapted to WC-MPS model to overcome the tensile instability and the noisy pressure fields that may affect sediment behaviour. These include an optimized particle shifting approach and a new numerical diffusion term. A visco-plastic rheological model based on local µ(I) rheology is used to predict the non-Newtonian behaviour of sediment continuum. The collapse of granular materials (a widely-used test case) is used as the benchmark of this study. The surface profiles and the runout distance of the granular deposits are compared and evaluated with those of the experimental measurements showing good compatibility. The implemented and adapted improvement techniques are proven to be effective in reproducing realistic sediment behaviours in different flow conditions.