Revolving rivers in sandpiles: from continuous to intermittent flows

TL;DR

This paper investigates the transition between continuous and intermittent revolving rivers in sandpile formation, providing experimental phase diagrams, improved models, and a dimensionality argument to explain the dynamics.

Contribution

It experimentally maps the phase diagram of sandpile regimes and refines the kinematic model to better understand river formation mechanisms.

Findings

Identified the conditions for continuous and intermittent river regimes.

Improved the kinematic model of sandpile topography.

Proposed a dimensionality reduction explanation for regime transitions.

Abstract

In a previous paper [Phys. Rev. Lett. 91, 014501 (2003)], the mechanism of "revolving rivers" for sandpile formation is reported: as a steady stream of dry sand is poured onto a horizontal surface, a pile forms which has a river of sand on one side owing from the apex of the pile to the edge of the base. For small piles the river is steady, or continuous. For larger piles, it becomes intermittent. In this paper we establish experimentally the "dynamical phase diagram" of the continuous and intermittent regimes, and give further details of the piles topography, improving the previous kinematic model to describe it and shedding further light on the mechanisms of river formation. Based on experiments in Hele-Shaw cells, we also propose that a simple dimensionality reduction argument can explain the transition between the continuous and intermittent dynamics.