Simulations of dense granular flow: Dynamic Arches and Spin Organization

TL;DR

This paper introduces a numerical model for 2D granular flow that captures crack formation, dynamic arch behavior, and organized particle spin structures, providing insights into the mechanisms of granular decompaction and flow.

Contribution

The study presents a detailed simulation of granular flow including crack dynamics, pressure effects, and particle spin organization, which advances understanding of dense granular material behavior.

Findings

Cracks originate at side walls and lead to pile fragmentation.

High collision rates correlate with organized angular velocity structures.

Dynamic arches influence crack formation and flow velocity.

Abstract

We present a numerical model for a two dimensional (2D) granular assembly, falling in a rectangular container when the bottom is removed. We observe the occurrence of cracks splitting the initial pile into pieces, like in experiments. We study in detail various mechanisms connected to the `discontinuous decompaction' of this granular material. In particular, we focus on the history of one single long range crack, from its origin at one side wall, until it breaks the assembly into two pieces. This event is correlated to an increase in the number of collisions, i.e. strong pressure, and to a momentum wave originated by one particle. Eventually, strong friction reduces the falling velocity such that the crack may open below the slow, high pressure `dynamic arch'. Furthermore, we report the presence of large, organized structures of the particles' angular velocities in the dense parts of the granulate when the number of collisions is large.