The flow rate of granular materials through an orifice

TL;DR

This paper investigates the flow rate of granular materials through orifices, providing comprehensive data and simulations, and introduces a new law that accurately models flow across all outlet sizes.

Contribution

It presents a new empirical law for granular flow rate that fits data across all orifice sizes, improving upon existing models.

Findings

Existing laws are only accurate for limited outlet sizes.

The new law fits experimental and simulation data for all sizes.

Flow behavior for very small and large outlets is accurately captured.

Abstract

The flow rate of grains through large orifices is known to be dependent on its diameter to a 5/2 power law. This relationship has been checked for big outlet sizes, whereas an empirical fitting parameter is needed to reproduce the behavior for small openings. In this work, we provide experimental data and numerical simulations covering a wide span of outlet sizes, both in three and two dimensions. This allows us to show that the laws that are usually employed are satisfactory only if a small range of openings is considered. We propose a new law for the mass flow rate of grains that correctly reproduces the data for all the orifice sizes, including the behaviors for very large and very small outlet sizes.