Abstract:

The effect of the geometric shape of ellipsoids (covering a wide aspect ratio range from 0.003 to 60) on the structure of adhesive loose packings is investigated by the random ballistic deposition method with the hit-stick-freeze assumption. Statistical results show that the packing density of spherical particles is the largest, which is 0.1469. As the particle shape deviates from spherical shape, the packing density decreases rapidly. When the aspect ratio is below 0.1 and above 10, the packing density is approximately correlated with the aspect ratio in 1 and -2 power-law relations. The local coordination number is independent of the particle shape, which not only follows the Gaussian normal distribution, but also has a common average value of 2.001. This result indicates that for packing systems of non-spherical particles controlled by short-range interparticle contact interactions, 2 is the lowest coordination number for forming a mechanically stable structure. The radial distribution function shows that the local packing structure is dominated by local minor-to-major and major-to-major contact for oblate ellipsoids, and by local minor-to-minor and minor-to-major contact for prolate ellipsoids. Finally, analogous to the classical filling theory of spherical particles, a predicting correlation between the packing density and the aspect ratio is established.

Key words: computer simulation, particle, deposition, particulate processes, random packing, non-spherical

摘要：

采用基于碰撞-黏附-冻结假设的随机弹道沉积方法，研究了椭球颗粒的几何形状（长径比变化范围为0.003~60）对黏附疏松堆积结构的影响。统计结果表明，球形颗粒的堆积密度最大，为0.1469。随着颗粒形状偏离球形，堆积密度迅速降低。当长径比小于0.1或大于10时，堆积密度与长径比之间分别近似服从1和-2的幂律关系。局部配位数与颗粒形状无关，不仅服从高斯分布，而且统计平均值均为2.001，表明对于短程接触相互作用控制的非球形颗粒堆积系统，形成力学稳定结构的最小配位数仍为2。径向分布函数表明，扁平形椭球的局部堆积结构由短轴-长轴和长轴-长轴接触主导，长条形椭球的局部堆积结构由短轴-短轴和短轴-长轴接触主导。最后，类比经典球形颗粒的填充理论，构建了堆积密度与长径比之间的预测关联式。

关键词: 计算机模拟, 粒子, 沉积物, 颗粒过程, 随机堆积, 非球形