Numerical Simulation Of Particle Material Fall, Bounce And Accumulation Process

Particle materials can be seen everywhere in production operation and daily activities, and which is the necessary material in the process of economic construction.In such the process just like storage, transport and use of particle materials, the phenomenon of particle free fall often occurs, which will escape into the air, causing local or even large area dust pollution. Dust into the air will bring about a series of environment problems. The particles associated with production process will harm to the health of the staff, ruin the production facilities and affect product quality.Particulate matter accumulated to a certain concentration may also lead to dust explosion, thus masses of particles into the air will cause a wide range of pollution,which is one of key to the reason that fog and haze frequently happen in the city of northern China in recent years. Free falling particles will cause a secondary dust when rebounded from the floor, which increases the dust particles contaminated area; the impact of falling material to stockpile also cause secondary dust. This paper, based on the gas-solid flow in previous studies, through analysis of gas-solid flow to find out the law of movement of particles in the air, lays the foundation of control of the dust caused by free-fall particles, and simulates the course of the particles bounce and accumulation.This paper use the UFD method to research the course of falling, rebound and accumulation of the spherical, uniform particle size particulate, using COMSOL Multiphysics5.0 which based on finite element computational fluid software. Use different modules to calculate the different process of particles falling, mainly including turbulence module, fluid flow and particle tracking module and moving mesh module.In the simulation study, the introduction of fluid and particle, based on the interaction between the drag force equation, Euler-Lagrange method is used in the standard _{k -e} turbulence model, achieve the two-way coupling between the fluid phase and the particulate phase, and by analyzing the variations of the fluid velocity and particle velocity, the correctness is verified in this article about the two-way coupling simulating gas-solid two phase flow; the Knudsen law and the Monte Carlo method is used to the simulation of random rebound the migration process in the paper,considering the loss of momentum of the particles and the wall colliding; relying on the grid morphing to reflect the process of particle packing is proposed during the research of the particle packing process. By introducing the accumulator as an intermediate variable, the volume of particles contacting with the wall is changed to the volume of mesh deformation. Eventually, the morphology of the particles is reflected by the deformation of the mesh. At the same time, the influence of the flow of the particles on the flow field is observed. The results show that: the larger particle size, the higher drop height, the greater density of the fluid makes the greater disturbance; particles in the fluid have greater influence and more complex than single particles, not simply plus results. The simulation of the particle rebound process realized the random situation of the momentum loss and the direction of the rebound. Through the deformation mesh to reflect the particle accumulation achieved ideal results, but compared with real particles accumulation is different. By comparing and analyzing the change of the velocity of the particles packing and do not build up, the accumulation of particles can’t be ignored in the study of the secondary dust particles problem.