# Granular flow from silos with rotating orifice

## TL;DR

This study demonstrates that rotating the bottom of a silo can sustain and enhance granular flow through small exits, with flow behavior influenced by rotation speed and exit position, transitioning from funnel to mass flow.

## Contribution

It introduces the effect of bottom rotation on granular flow rates in silos, revealing non-monotonic flow behavior and flow regime transitions not previously characterized.

## Key findings

- Flow rate follows Beverloo Law down to D=1.2d.
- Flow rate increases with rotation rate at small D.
- Flow transitions from funnel to mass flow with increased shear.

## Abstract

For granular materials falling through a circular exit at the bottom of a silo, no continuous flow can be sustained when the diameter D of the exit is less than 5 times the characteristic size of the grains. If the bottom of the silo rotates horizontally with respect to the wall of the silo, finite flow rate can be sustained even at small D. We investigate the effect of bottom rotation to the flow rate of a cylindrical silo filled with mono-disperse plastic beads of d = 6 mm diameter. We find that the flow rate W follows Beverloo Law down to D = 1.2d and that W increases with the rotation rate {\omega} in the small exit regime. If the exit is at an off-center distance R from the axis of the silo, W increases with rate of area swept by the exit. On the other hand, when the exit diameter is large, W decreases with rotation speed at small {\omega} but increases with {\omega} at large {\omega}. Such non-monotonic behavior of W on rotation speed may be explained as a gradual change from funnel flow to mass flow due to the shear at the bottom of the silo