Research Of Theory And Algorithm For Non-spherical Particle In3D DEM

Particulate or granular material is now being widely used in chemical, pharmaceutical,food and other industries. It is of great significant to understand the locomotory mechanism ofparticulate, which has many important applications in industry. In recent years, the relatedresearch in this area has attracted more and more attention. However, this problem has notbeen satisfactorily resolved due to the difficulty of the particle group research. Particulatesubordinates to the solid matter, which has a fixed shape and volume and to whichdeformation does not occur without external force. Discreteness and fluidity should beconsidered when study such kind of particulate. Traditional solid or fluid matter is notsuitable for it.Since the publication of researches of Cundall and Stack, the discrete element methodwhich was first proposed by Cundall is considered as an important tool for the simulation ofparticle motion. The basic idea of discrete element method is regarding a particle group ascollections of particles which have shape and quality. By using Newton’s second law ofmotion and dynamic relaxation method to calculation interaction forces, movement anddisplacement of each particle interaction between individuals and each particle, then themovement of particle groups can be computed by single time step iteration.The representation of particle shape is challenging as a key point in the discrete elementmethod simulation technology. However, most studies are tightly confined to the most simpleparticle shape, such as the2D disk or3D sphere, of which the diversity of real particles willbe modeled on simple shape modeling in order to develop a more complex shape particlemodeling.After years of concentrated efforts, our group has got a series of research results in theDEM theory and calculation, and accumulated a wealth of theoretical knowledge and practicalexperience. On the basis of the theoretical study in DEM, combined with agriculturalmachinery design knowledge, we have developed a set of DEM simulation software, whichhas designs, calculations, simulation demonstrates and performance analysis functions.The current simulation software in our group is base on Pro/E technology to completethe modeling for ellipsoid, super-sphere and other non-spherical particles. Although ourmethod can model complex shape of particles, it has defects for some kinds of irregular shapeparticles. This paper is written to give a better result for irregular shape particles. Based oncareful research of file structures and data structures on particles scanned3D model, a spheregenerated algorithm based on vertexes and triangular meshes is proposed, according to topological relations and geometric information of vertexes and triangular meshes, as particlescan pictures of3D model files is composed by multiple non-overlapping triangular meshsurfaces. In order to improve the similarity between the modeling particle and the real particle,a sphere generated filter algorithm is proposed to accomplish irregular shaped particlemodeling. By the modeling software of irregular particles, we can model the complex shapedmaterial with DXF format scanning files of particles, which can be used in DEM. Based oncurrent simulation software of our group, we integrate the particle model software and the3DDEM simulation software，and complete the model of non-spherical in3D DEM software.In irregular shaped particles modeling software, non-spherical particles can berepresented by overlapped spheres, which is very useful to the research of non-sphericalparticles DEM calculation. Based on our formal research on combination of ellipsoid particlesof DEM, we use neighbor search method of boxes to do neighbor search, contact detection,contact overlap and contact force computation of irregular particles, then we establish DEMcalculation of irregular particles.Finally, the paper gives requirements analysis of particle modeling software andnon-spherical particle discrete element calculation software, illustrates data flow, classes andcases diagrams of the system. Functional presentation explains main functions of the twosoftware and analyzes key technologies. Testing stage tests the stability and correctness of thecalculation results by unit testing and integration testing.