Numerical Simulation Of Riprap Drifting In Water Using A CFD-DEM Coupling Method

Riprap construction is a common way of operation in river improvement and damming.After the block stone is thrown,it will drift due to the action of water flow during the settlement process.Except the influence of water flow,The particles of block stone collide with each other in the block stone group,which influent the drifting of riprap group.The position where a block stone falls underwater will be more difficult to determine.If riprap does not reach the designated position,easy to cause the waste block stone materials,labor costs increase.In this paper,the computational fluid dynamics program OpenFOAM and the discrete element program LAMMPS are coupled by using SediFoam which is a solver based on CFD-DEM coupling.The numerical model of solid-liquid two-phase flow was established.The underwater drift movement process of riprap is simulated.The motion characteristics of single particle riprap and block stone group riprap were analyzed.Provide basis for project construction.This paper focuses on the drift characteristics of riprap under high water depth and high velocity.Before calculation,Ergun-Wen-Yu and Syamlal drag force models were compared.Determine the appropriate drag force model.The appropriate computational grid is determined by grid sensitivity analysis.The drift process of single particle block stone and block stone group in water was simulated with numerical model.The correctness of the numerical model is verified by using the experimental data of physical model.The model block stone and prototype block stone are calculated respectively in a single particle stone drifting simulation.The drift distance between the two kinds of blocks is very close.The calculation result of drift distance is slightly larger than that of model experiment.The calculated drift track of the block stone tends to a straight line.The combination of block stones with equal diameter and two combination methods of block stones with different diameters are adopted.The underwater drift process of block stone group is simulated.The combination of particles with diffirent diameters has a certain effect on the drift simulation results of block stones.The distribution morphology,drift and diffusion range,average drift distance and distribution area of the block stone particles after falling to the bed are compared with the model experiment.The simulation results show that the results obtained by using the combination of blocks with equal diameter are more consistent with the model experimental results than those obtained by using two kinds of blocks with different diameters.In the end,the paper analyzes the morphological change and collision between the blocks in detail.