The Improvement Research Of Three-dimensional DEM Software

There are a lot of granular material in the real world, such as the floating dust inthe air, sand and gravel rolling on the ground, coral reefs particles in the ups anddowns which is shattered in the sea. And such as the fertilizers used in agriculturalproduction, soybean, corn, wheat in the agricultural products. Also, the granular drugsin the field of medical treatment, the granule raw materials and products in the field ofchemical industry. We can know that the granular matter exists in our production andlife very widely, more can be said that the material world is the world of the particles.The study of particles can also help us to know the world, to the improvement ofproduction and life style.Particles have discreteness and liquidity. We cannot adopt the traditional methodof fluid and solid mechanics on the study of particles. Since the discrete elementmethod is put forward by professor Cundall, the discrete element method becomes theimportant way to study particle movement. The basic principle of DEM is that weregard the particle group as a collection of particles which have a certain shape, andwe calculate each particle movement by applying the methods of the dynamicrelaxation and the time step iteration method, etc. Finally, we finish calculating themovement process of particle groups.We can use the ball particle model to simulate real particles which like a ball. Butwhen we use the ball particle model to simulate those irregular shape particles, theresult is not bad. That is not a good ideal. We can use the particle model which is notthe ball particle model, and we call it non-spherical particle model. The surface ofnon-spherical particle can also be irregular, and a lot of simple ball particles filled inthe non-spherical particle. In the simulation, for achieving the purpose of simulationof ball particle movement, calculate the internal force of the small ball model tocalculate the force of non-spherical particle. It is important to simulate any motionprocess for a good algorithm. So we know that it is important to simulatenon-spherical particle for finding a algorithm which is suitable for non-sphericalparticle. After years of unremitting efforts, this research group already has a richtheoretical basis and perfect system structure to design three-dimensional DEMSoftware. But there are still some defects which should be improved, for example thesimulation results of non-spherical particle is bad. Storage functions of the software isnot perfect, and it can only save all the movement information of stress, velocity,displacement and flow, so we can know we do not have selectivity. For non-sphericalparticle, the software have not achieved simulation of the same type of particle whichhave different mechanical properties. There are other practical functions which is notrealized, etc.On the basis of the study of the available algorithms for calculating thenon-spherical particle, this paper explores two aspects which are the collisionsbetween the non-spherical particles and the collisions between non-spherical particlesand the boundary. This paper researches contact detection process between thenon-spherical particles, contact force calculation between the non-spherical particles,contact force calculation between the non-spherical particles and the boundary and themovement solving process of non-spherical particles. This paper sets up a set ofsolution of the algorithm during the process of non-spherical particle movement, andthe paper programmes to realize three-dimensional DEM calculation-simulationSoftware which applies the improved computing algorithm of non-spherical particle.We can see that simulation effect of non-spherical particle is very vivid through a lotof testing. That proved that the improved the ball the correctness of the computingalgorithm of non-spherical particle, and verified the reliability of the software.Several practical functions have added to three-dimensional DEM Software inthis paper. They are the function of more properties of non-spherical particlecomputing, the function of calculation results of selective preservation, the function ofquick playing, the function of setting the velocity of particles and the function ofsetting the generated speed of particles. When we use the software to simulate, we canuse non-spherical particles which have the same geometric model and differentmechanical properties by using the function of more properties of non-sphericalparticle computing. That is to say we can simulate the same type of non-sphericalparticles, but these non-spherical particles can have different physical parameters suchas shape, density, mass, damping coefficient and stiffness coefficient. So that thesimulation of software is closer to reality. If we want to use the function of calculationresults of selective preservation, before starting the calculation, we need to set one or more of the movement information through interface controlling, such as stress,velocity, displacement and flow. This function provides users with free choice space,at the same time it also reduces the storage capacity. This paper realized the functionof quick playing through controlling the reading contents of the results file, and thisfunction help user understand the calculation results of the software more effective. Ifwe want to use the function of setting the velocity of particles, before starting thecalculation, we need to set the value of the speed on the x through interfacecontrolling to control the initial speed of the particles, and we need to set the value ofthe speed on the y, finally, we also need to set the value of the speed on the z. We canset the value of generating speed of particles to control the number of generatedparticles in a time step. The last two functions make the software to meet therequirements of user. At the last, the each testing of the new functions verified that thefunctions possess availability and practicability.