Shape dependence of resistance force exerted on an obstacle placed in a gravity-driven granular silo flow

TL;DR

This study investigates how the shape of an obstacle affects the resistance force in a gravity-driven granular silo flow through experiments and simulations, revealing a weak shape dependence characterized by a dimensionless force parameter.

Contribution

It introduces a new dimensionless number to characterize resistance force in granular flow, highlighting its weak dependence on obstacle shape, which is a novel finding.

Findings

Resistance force is weakly dependent on obstacle shape.

A dimensionless number characterizing force balance is independent of flow rate.

The effective flow width interacting with the obstacle is identified.

Abstract

Resistance force exerted on an obstacle in a gravity-driven slow granular silo flow is studied by experiments and numerical simulations. In a two-dimensional granular silo, an obstacle is placed just above the exit. Then, steady discharge flow is made and its flow rate can be controlled by the width of exit and the position of obstacle. During the discharge of particles, flow rate and resistance force exerting on the obstacle are measured. Using the obtained data, a dimensionless number characterizing the force balance in granular flow is defined by the relation between the discharge flow rate and resistance-force decreasing rate. The dimensionless number is independent of flow rate. Rather, we find the weak shape dependence of the dimensionless number. This tendency is a unique feature for the resistance force in granular silo flow. It characterizes the effective flow width interacting with the obstacle in granular silo flow.