The term "granular material" refers to a system composed of a large number of discrete,
macroscopic, solid particles. It has been estimated that nearly 80% of everything that is
produced industrially or agriculturally in the United States exists, at one time or another during
its processing or manufacture, in granular form [1]. For this reason, understanding the behavior
and properties of granular materials is a matter of considerable practical and economic
importance. Sands, gravels, and soils must be handled in the building and construction industry,
granular ores are utilized to make metal alloys and components, grains are a necessary ingredient
in the manufacture of numerous foods, and the pharmaceutical industry makes medications from
chemicals and natural products in powdered and granular form.