颗粒形状对颗粒体系的动力学行为影响显著，非球形颗粒体系表现出了比球形颗粒体系更为复杂的性质。颗粒形状影响体系在气体、液体、晶体或玻璃态下的结构以及这些态之间的相转变特性。非球形颗粒体系的研究得到了越来越多的关注。现有非球形颗粒体系的离散元模拟多针对凸形颗粒，但就研究趋势而言，朝凹形颗粒发展是确定的也是必然的。凹形颗粒体系在流动、阻塞、最密随机堆积等过程中会表现出来一些和凸形颗粒体系不同的性质。而凹形颗粒体系在自然界或工农业生产中又是无处不在的，其性质的研究无论是在科学或工程上都具有十分重要的意义。本项目拟用网格法求取凹形颗粒间接触点，研究描述凹形颗粒间多个接触点的数据结构和搜索更新算法，结合多种法、切向力接触模型编写凹形颗粒体系离散元程序，并针对不同的颗粒体系（重力作用下的堆积、最密随机堆积等问题）对程序的稳定性、正确性予以验证，为用离散元法研究凹形颗粒体系的物理性质提供技术上的帮助。

Particle shape has a significant influence on the dynamic behavior of particle system. The properties of the non-spherical particle system are more complex than those of the spherical particle system. The structure of liquids, crystals, and glasses is intimately related to particle shape, as are the transitions between these phases. Thus, research on the non-spherical particle system has gained increasing attentions. The existing discrete element simulation of non-spherical particle system is mostly about the convex particle, but as indicated by current research trends, the simulation of the concave particle system is urgent and inevitable. Moreover, concave particle system exhibits some properties which are different from those of convex particle system in the processes of particle flow, jamming, and maximally dense random packing. The concave particle system is ubiquitous in nature or industry and agriculture, and its research is of great practical significance in science or engineering. In current proposal, we are going to adopt the grid method to determine the contact points between concave particles. The data structure and search update algorithm of multiple contact points between concave particles will be studied, and then, the discrete element program which can simulate the concave particle system will be written in combination with different normal and tangential contact models. Furthermore, different particle systems (such as the packing under gravity, random close packing) will be applied to verify the stability and validity of the program and the research can provide technical supports in the study of physical properties of concave particle system by the discrete element method.