Simulation Analysts Of Sinking Process Of Particles Falling Into Water Based On Coupled DEM-CFD

Riprapping operation has been widely existed in the coastal areas of China, which is afundamental operating type. For example, revetment works and flood control emergency inagricultural water conservancy project, as well as port construction, bridge foundationsprotection, etc. However, after block stones were thrown into the water, they will not onlybe affected by water and their own gravity, but also be affected by other stones’ collision. Ifthe stones could not reach the designated position, they would not achieve the desiredeffect of fixing the foundation, and increase the load of the foundation, which result inincreasing labor costs and reducing operational efficiency. Therefore it is necessary to studythe sinking process of block stones in riprapping operation.In order to simulate the sinking process of block stones in riprapping operation, thispaper does a test of particles sinking in the laboratory. Two types of particles (glassparticles and pebbles) and water are treated as research objects in the test. By usinghigh-speed camera technology, the trajectory of particles are tracked, the simulationparameters and comparative data are obtained. On this basis, the sinking process ofparticles is simulated by using DEM-CFD coupling method. This paper is based ondomestic and foreign solid-liquid coupling theory. The particles are regarded as a discretesystem, their movements are obtained by Newton’s laws, named as Discrete ElementMethod (DEM); the liquid is regarded as continuum, its movement is obtained by solvingthe Navier-Stokes equations, named as Computational Fluid Dynamics (CFD); finally, thesinking process of different particle models are simulated by coupling EDEM-FLUENTsoftware. The effectiveness of the method is verified by comparing the simulation andtesting. It may be helpful of providing reference for riprapping operation, simplifying theconstruction process, improving operational efficiency and reducing labor costs. The mainwork and the results of the paper are as follows.(1) The research status of riprapping operation and solid-liquid two-phase flow,DEM-CFD coupling theory and its applications have been discussed and summarized.(2) As the need for solid-liquid coupling simulation, the physical and mechanicalparameters of6kinds of particles (spherical glass particles, non-spherical glass particles,pebblesⅠ, pebblesⅡ, pebblesⅢ and pebbles Ⅳ) have been tested and calculated,including diameter, triaxial size, density, coefficient of static friction, elastic modulus and shear modulus.(3) In order to simulate the sinking process of block stones in riprapping operation, atest of particles sinking in still and moving water have been done in the laboratory. Byusing high-speed camera technology, the trajectory of particles were tracked, the simulationparameters and comparative data are obtained, including restitution coefficient ofparticle-wall and particle-particle, vertical height and speed changes by time of the particleduring falling and rebounding, the trajectory and distance of the particle during sinking.(4) The process of particles sinking has been simulated by using DEM-CFD couplingmethod. Firstly, the geometric models of particles and glass have been established, relatedparameters have been set in the software. Secondly, the particle models of combination andequivalent spherical ball sinking in still and moving water have been simulated. Finally, thesimulation results and experimental results have been analyzed comparatively. Theeffectiveness of particles sinking in water using DEM-CFD coupling method has beenproved initially, and a new approach to study the theoretical of riprapping operation hasbeen provided.