Formation of longitudinal structures in granular flows

TL;DR

This paper presents a theoretical explanation for the formation of longitudinal structures in granular flows, linking fluidization feedback and lateral stress to a convective instability, aligning with experimental observations.

Contribution

It introduces a new theory connecting fluidization and lateral stress feedback to structure formation in granular flows, explaining experimental features.

Findings

Longitudinal structures result from a convective instability.

Structure formation involves positive feedback between fluidization and lateral stress.

Theory explains the appearance and non-stationary behavior of structures.

Abstract

In the framework of the theory of partially fluidized granular flows we study the formation of longitudinal structures observed experimentally by Forterre and Pouliquen in a flow down a rough inclined plane. We show that the formation of longitudinal structures is related to the positive feedback between the fluidization rate and the lateral stress (side pressure), which leads to a convective instability. Our theory explains main experimental features, such as appearance and amplification of the structure at some distance from the outlet and non-stationary behavior of the structures.