Multiphase particle method using an elastoplastic solid phase model for the diffusion of dumped sand from a split hopper

•Sand dumping experiment and simulation using ISPH with sand-fluid multiphase model are conducted.•The model exchanging sediments between sand and fluid particles is implemented.•An advection-diffusion equation for transport of suspended sediments is incorporated.•The present study shows the necessity of suspended sediments to predict a deposition area accurately. It is necessary to accurately predict the diffusion and deposition range of a large amount of sand dumped from a hopper barge for efficient reclamation in a coastal area. Many previous studies have proposed useful models to simulate the diffusion behavior of sand in fluid; however, most of their models have not considered the deposition of sand. This study proposes a particle-based numerical model that includes fluid-sand interaction. The model utilizes two methods to track the sand: an elastoplastic model for a sand layer and an advection-diffusion model for suspended sediments. These two techniques for sand tracking enable the evaluation of diffusion and deposition more accurately in a series of sand processes from inside the hopper to the seafloor. The proposed model was validated with a dam-break simulation using fluid and saturated sand. In this validation, the time histories of the runout distance of the dam-break flow and the final deposition shape of the sand were compared, and they agreed well with previous experimental results. Thereafter, we conducted an experiment in which sand was dumped from a split hopper, and the model was validated using the results of this experiment. The performance of the model was examined, focusing on the spread of the suspended sediments, the velocity field of the fluid, and the deposition of sand. The flow characteristics induced by the dumped sand were revealed from the calculated results.