Effect of grain anisotropy on ordering, stability and dynamics in granular systems

With experiments and simulations, we show that monomer, dimer, and trimer beads in 2D represent an ideal system in which specific types of order, dynamics, and granular stability can be controlled. We determine the distinct types of ordering for increasing grain anisotropy. Dimers possess a quasi-ordered state in which translational but not orientational order exists, while trimers are disordered. We show that these different orderings give rise to specific types of flow. Monomers show a large-scale collective ordered shear motion, dimers show tumbling motion near the surface, and trimers show disorderly bulk tumbling.