颗粒离散元法模型及其在农业工程中应用的研究

Granule materials are common in engineering. The complexity in the mechanical or dynamic analysis makes it to be a difficult problem in relevant technology. The Discrete Element Method (DEM) has been proved as a useful tool in analyzing such behaviors, but the theory and applications still remain problems. This project has focused on the simulation for dry particle assemblies and the modeling for wet particle assemblies utilizing advanced DEM models for spherical particles based on the contact mechanics theory.With the advanced program, the simulation study on silo discharge, the dynamics of particle assemblies within a truck during sudden braking and under vibration, as well as earth retaining wall problem was preceded. For silo discharge, it was proved that the material modulus has little effects on the granule flow, and its crushing results from the buckling of the vertical wall due to sharp increase of shear friction. The study on truck braking and vibration gives many information which is useful for design. The study on retaining wall also has some progress. The study on modeling for the wet granule is highlighted for its new mathematical work. Besides the work for interstitial Newtonian fluids, up to date there is little progress for non-Newtonian fluids used for DEM simulation owing to the complicated constitutive relation. Analysis for the interaction between two spheres with a Power-Law fluid and Bingham one was proceeded utilizing mathematic techniques, which is useful for implementation into DEM code so as to undergo DEM simulation for various wet granules such as soil dynamics, foundation with interstitial water and ice-crystal based foods for various application. The progress of the project provides good understanding on advanced DEM methodology for efficient simulation on dry granules in applications and a breakthrough in modeling wet ranules.

散体物理料的力学运动学行为是力学研究的一个重要方向，也是工程界普遍关注的课题。离散元法颗粒系统是研究上述行的新的有效数值方法。本项目采用先进的三维球元模型，结合农业工程背景的若干典型问题进行多侧面的建模、简化和数值模拟分析。本项目将深化对不同性态散体物料在处理时的相互作用和运动的认识，并为相关的工程设计提供理论依据。.