Grain sizes and shapes are relevant features when studying the physical properties of granular systems. This is the reason why many industries focus their efforts into technologies for controlling / measuring particle morphologies.

In a recent article, we demonstrate that non-convex particles present multiple contacts, therefore deeply modifying the physics of random packing. Non trivial effects are evidenced. Among others, non-convex grains lead to low density random packings which exhibit more stability than random sphere assemblies ! This is due to the interlocking of grains, i.e. the development of highly connected force networks in the grain structure.

F.Ludewig and N.Vandewalle, Phys. Rev. E 85, 051307 (2012) – PDF

UPDATE : a similar study with U-shaped grains has been published recently.