Structure analysis on the packing of ellipsoids under one-dimensional vibration and periodic boundary conditions

This paper presents a numerical study on the packing structure of ellipsoidal particles under one-dimensional vibration and periodic boundary conditions by discrete element method. It is shown that after vibration, packings of ellipsoids become denser, and the coordination number increases slightly for oblate ellipsoids (aspect ratio between 0.25 and 0.75), but decreases for most of the prolate ellipsoids due to the conspicuous excluded volume effects. It is found that packings of ellipsoids are more random after vibration, showing opposite trend to spheres. The analysis of Voronoi tessellation for ellipsoids packing indicates that after vibration, some bridges or arches collapse, and particles reorganize to fill voids, leading to denser packings. The Voronoi cell volume becomes smaller for both oblate and prolate particles, and more uniform for oblate particles. Therefore, the bed becomes densely packed by obtaining smaller and more uniform Voronoi cell (or void structure) at the sacrifice of particle orientational order.