Numerical Simulation Study Of The Free Falling And Accumulation Of The Particle Plume

Granular materials are widely encountered in the nature and industrial applications. In the industrial production, the phenomenon such as the storage, handling and transportation of the granular materials often occurs. During the processing, granular materials can often free fall in air environment, which will generate dust when the granular materials are influenced by the ambient air as well as their own motion. The dust will bring a variety of hazards to the industrial production, and even the health of people. The accumulation of particles may also appear secondary dust due to the impact of the free falling particles and air, which will make the environmental quality deteriorated. Therefore, the free fall particles is studied to master the movement characteristics of particles and air and the mechanism of particle dispersion, which can lay the foundation for controlling the dust and designing effective dust control system.Due to the influence of gravity, the interaction between particles and ambient air, the collisions of particle-particle and particle-wall, and the complex condition of accumulation when the falling particle contact the bottom wall, it is difficult to study the motion mechanism of free falling particle through the experimental analysis in detail. In addition, with the increasing performance of the computer hardware and the popularization of different application software, the results obtained by using the numerical simulation method become more accurate. Considering the complex mechanism of the free falling granular material, this paper simulates the free falling particles from two parts. First, this paper uses the computational fluid dynamics software Fluent with two-way coupling method to simulate free falling particle plume flow. In this section, the gravity and the interaction forces between particles and fluid are considered as well as ignoring the particles’ accumulation process. Second, using the discrete element software EDEM simulate the particles’ falling and accumulation process. The interaction of particle-particle and particle-wall is considered, but the influence of fluid is ignored in this simulation.In this paper, the numerical simulation method is used to study the falling granular material. The interaction of fluid flow and particles with different mass flux, different particle size and different density was analyzed. In addition, the accumulation process of particles and the influence on the following particles are obtained by simulation.For a dilute gas-solid two phase flow, when the interaction force between particle and particle can be ignored, meanwhile the interaction between particle and fluid is considered, the Fluent is used to simulate the dilute gas-solid two phase flow, of which the gas phase is solved using the standard k-? turbulence model, and the particle’ motion is calculated according to Newton’s second law. The simulation results show that the particles with lager mass flow rate, the larger density, and smaller particle size will diffuse widely, and bring the greater influence to the fluid flow. At the same time, the velocity of the particles with different physical parameters has the same trend at the axis. When the particles are falling, the axial velocity increases during the fall until to a position where the speed reaches the maximum, then the axial velocity decreases gradually until the particle contact the lower wall.For the flow field can be ignored, this paper uses the discrete element method software EDEM to simulate the particles’ falling and accumulation. Using the soft-particle model calculate the interaction force of the particle-particle and particle-wall. Simulation results show that the collisions between particle and particle cause great influence to the flow status of particles, and the falling particle impact the existing packing particles to make the rest particles produced a number of secondary splash particle at the lower wall. Using the discrete element method to simulate accumulation process of particles has achieved some results, but it still need to improve.Above all, for the numerical simulation of the free falling particles, different algorithms can be used in different situations. In addition, the paper lay the foundation for the following simulation of the free falling particle plume through using the four-way coupling method that is CFD-DEM method which the computational fluid mechanics and the discrete element method are coupled.