Pattern Formation in Confined Granular Systems

Abstract

There are many open questions involving the displacement of granular materials in confined systems, in particular, the flow through a Hele-Shaw cell in the quasistatic regime. It was shown that, in some cases, there is a spontaneous formation of fingers during the injection of grains into a confined system. In this work, the objective is to study the pattern formation in this kind of flow, using Molecular Dynamics simulations. Some parameters were chosen to determine their role in the development of fingers: the friction coefficient between the particles, the friction coefficient between the grains and the cell plates, the grain size distribution (monodisperse, polydisperse or bidisperse systems). The force distribution was analyzed, as well the stress components. We have observed that the monodisperse systems have a higher tendency for fingers formation, displaying a hexagonal symmetry. We also evince a higher stress field close to the fingers tips, in analogy to the Saffman-Taylor fingering phenomenon