Exponential and power law distribution of mass clusters in a (magnetic-like) deposition model of elongated grains in 2D piles

摘要

A generalized so called magnetically controlled ballistic rain-likedeposition (MBD) model of granular piles has been numerically investigated in2D. The grains are taken to be elongated disks whence characterized by atwo-state scalar degree of freedom, called ''nip'', their interaction beingdescribed through a Hamiltonian. Results are discussed in order to search forthe effect of nip flip (or grain rotation from vertical to horizontal andconversely) probability in building a granular pile. The characteristics ofcreation of + (or $-$) nip's clusters and clusters of holes (missing nips) areanalyzed. Two different cluster-mass regimes have been identified, through thecluster-mass distribution function which can be exponential or have a power lawform depending on whether the nip flip (or grain rotation) probability is largeor small. Analytical forms of the exponent are empirically found in terms ofthe Hamiltonian parameters.