Delaney Gary W, Hilton James E, Cleary Paul W
CSIRO Mathematics, Informatics and Statistics, Clayton South, VIC 3169, Australia.
Phys Rev E Stat Nonlin Soft Matter Phys. 2011 May;83(5 Pt 1):051305. doi: 10.1103/PhysRevE.83.051305. Epub 2011 May 24.
The concept of "random loose packing" (RLP) has evolved through extensive study of loose packings of spheres, which has resulted in an accepted definition as the loosest packing that can be obtained by pouring grains. We extend this consideration to packings of nonspherical grains (ellipsoids) formed by slow settling in a viscous liquid, and perform a detailed analysis of the structural properties of the resulting packings. We find that as in the case of spheres the loosest ellipsoid packings are generated for grains with high interparticle friction. However, unlike spheres, these packings cannot be considered random as they have a significant degree of orientational ordering that increases with the grain's aspect ratio. This demonstrates that applying sedimentation or pouring techniques that have become part of the commonly held definition of RLP, will not generate random packings of ellipsoids. The consequences for the accepted definition of RLP and its applicability to nonspherical grains is discussed.
“随机松散堆积”（RLP）的概念是通过对球体松散堆积的广泛研究而演变而来的，这导致了一个被广泛接受的定义，即通过倾倒颗粒所能获得的最松散堆积。我们将这一考量扩展到由粘性液体中缓慢沉降形成的非球形颗粒（椭球体）的堆积，并对所得堆积的结构特性进行了详细分析。我们发现，与球体情况一样，对于颗粒间摩擦力大的颗粒会产生最松散的椭球体堆积。然而，与球体不同的是，这些堆积不能被视为随机的，因为它们具有显著程度的取向有序性，且这种有序性会随着颗粒的纵横比增加。这表明，应用已成为RLP普遍定义一部分的沉降或倾倒技术，不会产生椭球体的随机堆积。本文讨论了RLP公认定义及其对非球形颗粒适用性的相关后果。
