Statistical properties of gravity-driven granular discharge flow under the influence of an obstacle

TL;DR

This study experimentally investigates how an obstacle influences gravity-driven granular discharge flow in a Hele-Shaw cell, revealing that the obstacle significantly alters flow dynamics, especially when positioned close to the exit.

Contribution

The paper provides new experimental insights into the particle-level dynamics of granular flow affected by obstacles, highlighting the impact on flow rate, temperature, and packing fraction.

Findings

Obstacle increases horizontal granular temperature.

Obstacle decreases packing fraction.

Effect is prominent when obstacle is within 6 particle diameters of exit.

Abstract

Two-dimensional granular discharge flow driven by gravity under the influence of an obstacle is experimentally investigated. A horizontal exit of width $W$ is opened at the bottom of vertical Hele-Shaw cell filled with stainless-steel particles to start the discharge flow. In this experiment, a circular obstacle is placed in front of the exit. Thus, the distance between the exit and obstacle $L$ is also an important parameter. During the discharge, granular-flow state is acquired by a high-speed camera. The bulk discharge-flow rate is also measured by load cell sensors. The obtained high-speed-image data are analyzed to clarify the particle-level granular-flow dynamics. Using the measured data, we find that the obstacle above the exit affects the granular-flow field. Specifically, the existence of obstacle results in large horizontal granular temperature and small packing fraction. This tendency becomes significant when $L$ is smaller than approximately 6$D_g$ when $W \simeq 4 D_g$, where $D_g$ is diameter of particles.