The Coupled CFD-DEM Method Based On High-Order Discretization Schemes And Its Application

Fluid-solid interaction has been widely used in nature and production，such as thesandstorm flow, pneumatic conveying, the process of fluidization, etc. The air-blowingseed-metering device can also be treated as the research object of fluid-solid interaction, theseed and the gas existing in seed room is treated as the solid phase and fluid phaserespectively, and they interact with each other and then form a fluid-solid interactionphenomenon.In this paper, a kind of precision air-blowing seed-metering device was treated asresearch object, and a digital design method based on the coupled CFD and DEM methodwas established by researching the theory of Computational Fluid Dynamics (CFD), DiscreteElement Method (DEM) and gas-solid flow. The method introduced CFD method built onthe Discrete Element Method, and taked advantage of the DEM and CFD respectively so asto reflect the interaction between the soil particles and the mechanical boundary or the flowfield, which established a kind of new method for optimization design of the metering device.The main work and results of the paper were as follows.Firstly, the development and the latest progress of CFD and DEM was introducedbriefly. A general solution procedure of the coupled CFD and DEM method was alsosummarized.Secondly, a mathematical model of3-D gas-solid coupling based on high-orderdiscretization schemes was developed. In the model, the discrete equations of fluid dynamicswas established by the high-order discretization schemes (Second Order Upwind Scheme,Quadratic Upwind Interpolation of Convective Kinematics), and SIMPLER method wasapplied to solve the discrete equation, and then the velocity field and pressure distributionwere got. Interaction force between the gas and the solid was calculated with semi-empiricalformulas and was used for the force analysis between discrete particles. This part formed thetheoretical basis of the3-D CFD-DEM simulation software.Thirdly, the simulation effect of the fluid-solid coupling simulation program was tested.In the situation without particles, the simulation of channel flow and lid driven flow wasconducted. The trend of velocity field was in keeping with the results of FLUENT softwareby use of the QUICK scheme, and the velocity values were also close. In contrast，the resultsof square cavity model wasn’t satisfactory by use of the Second Order Upwind Scheme.Then in the situation with particles, the simulation of the pneumatic conveying pipeline wasconducted. The results proved that it occured the two-way coupling interaction betweenparticles and gas. The simulated calculation results demonstrated that the method based on the coupled CFD-DEM was correct.Finally, simulation analysis was conducted on the working process of air-blowingseed-metering device. The3-D discrete element method analytical models of theseeding-metering device and soybean seeds with suitable mechanical model and simulationparameters were built. The working process of air-blowing seed-metering device wassimulated and analyzed by the self-developed3-D coupled CFD-DEM software, it showedthat the metering performance of simulation was good agree with the experiment results bycomparing the analytical results of simulation. This result demonstrated the feasibility ofusing the coupled CFD and DEM method to analyze the performance of the air-blowingseed-metering device. Therefore, the coupled CFD and DEM method provided a new kindmethod for the design and performance evaluation of the air-blowing seed-metering device.