Transient response in granular quasi-2D bounded heap flow

TL;DR

This study investigates the transient flow behavior in granular heaps when the feed rate changes suddenly, revealing a propagating wedge front and modeling the transition with a diffusion-like equation.

Contribution

It introduces a combined experimental and simulation analysis of transient flow in granular heaps and develops a moving boundary model based on local mass balance.

Findings

Wedge of flowing particles propagates downstream with velocity inversely proportional to square root of time.

Transient process continues after the wedge front reaches the downstream wall.

Model accurately describes the transition dynamics using a diffusion-like equation.

Abstract

We study the transition between steady flows of non-cohesive granular materials in quasi-2D bounded heaps by suddenly changing the feed rate. In both experiments and simulations, the primary feature of the transition is a wedge of flowing particles that propagates downstream over the rising free surface with a wedge front velocity inversely proportional to the square root of time. An additional longer duration transient process continues after the wedge front reaches the downstream wall. The entire transition is well modeled as a moving boundary problem with a diffusion-like equation derived from local mass balance and a local relation between the flux and the surface slope.