Discrete element method (DEM) has achieved considerable success on simulating complex granular material behaviours. One of the key challenges of DEM simulations is how to describe particles with realistic geometries. Many shape description methods have been developed including sphere-clustering, polyhedrons, sphero-polyhedrons, superquadric particles to name a few. However, to model general shaped particles with round features , these techniques are either introducing artificial surface roughness or are limited to a few regular shapes. Here we proposed a metaball based DEM where the metaball equation is used to describe particle shapes. Because of its flexibility on choosing control points in the metaball equation, many complex shaped particles can be modelled within this framework. The particle collision is handled by solving an optimization problem. A Newton–Raphson method based algorithm of finding the closest points for metaball DEM is developed accordingly. Using 3D printed particles, the proposed scheme is validated by comparing the simulated ran-out distance with granular column collapses experimental results. The model is further applied to study shape effects on vibration induced segregations. It is shown that the proposed metaball DEM can capture shape influence which may crucial in many engineering and science applications.

离散元方法（DEM）在模拟复杂的颗粒物料行为方面取得了相当大的成功。DEM模拟的主要挑战之一是如何描述具有逼真的几何形状的粒子。已经开发了许多形状描述方法，包括球形聚类，多面体，球面多面体，超二次粒子等。但是，为了对具有圆形特征的一般形状的粒子建模，这些技术要么引入了人工表面粗糙度，要么被限制为一些常规形状。在这里，我们提出了一种基于metaball的DEM，其中metaball方程用于描述粒子形状。由于它在选择元球方程中的控制点方面具有灵活性，因此可以在此框架内对许多复杂形状的粒子进行建模。通过解决优化问题来处理粒子碰撞。相应地，开发了一种基于牛顿-拉夫森方法的算法，该算法可找到元球DEM的最近点。使用3D打印的粒子，通过比较模拟的展开距离与颗粒柱塌陷的实验结果来验证所提出的方案。该模型进一步应用于研究形状对振动引起的偏析的影响。结果表明，拟议的元球DEM可以捕获形状影响，这在许多工程和科学应用中可能至关重要。该模型进一步应用于研究形状对振动引起的偏析的影响。结果表明，拟议的元球DEM可以捕获形状影响，这在许多工程和科学应用中可能至关重要。该模型进一步应用于研究形状对振动引起的偏析的影响。结果表明，拟议的元球DEM可以捕获形状影响，这在许多工程和科学应用中可能至关重要。