ABSTRACT
It is well known that there is a wide, and at present, unbridgeable, gap between microscopic and macroscopic granular mechanics. The main reason is not difficult to find: granular materials are inherently discrete with particle rotation and a grain length scale, which are much larger than those of molecular solid and fluid materials for which classical continuum theories were developed. In attempts to narrow the gap, several researchers have measured the rotation field within an assembly of granular material and then compared it with the continuum spin of the assembly (Bardet, 1994; Calvetti et al. 1997; Misra & Jiang, 1997; Dedecker et al. 2000), by using Distinct Element Method (DEM) (Cundall & Strack, 1979). In these studies, the rotation field was determined solely in terms of particle rotations, and was regarded approximate to the continuum spin.
