Enhanced flow rate by the concentration mechanism of Tetris particles when discharged from a hopper with an obstacle
Journal
Physical Review E
Journal Volume
103
Journal Issue
6
Date Issued
2021
Author(s)
Abstract
We apply a holistic two-dimensional (2D) Tetris-like model, where particles move based on prescribed rules, to investigate the flow rate enhancement from a hopper. This phenomenon was originally reported in the literature as a feature of placing an obstacle at an optimal location near the exit of a hopper discharging athermal granular particles under gravity. We find that this phenomenon is limited to a system of sufficiently many particles. In addition to the waiting room effect, another mechanism able to explain and create the flow rate enhancement is the concentration mechanism of particles on their way to reaching the hopper exit after passing the obstacle. We elucidate the concentration mechanism by decomposing the flow rate into its constituent variables: the local area packing fraction φlE and the averaged particle velocity vyE at the hopper exit. In comparison to the case without an obstacle, our results show that an optimally placed obstacle can create a net flow rate enhancement of relatively weakly driven particles, caused by the exit-bottleneck coupling if φlE>φoc, where φoc is a characteristic area packing fraction marking a transition from fast to slow flow regimes of Tetris particles. Utilizing the concentration mechanism by artificially guiding particles into the central sparse space under the obstacle or narrowing the hopper exit angle under the obstacle, we can create a manmade flow rate peak of relatively strongly driven particles that initially exhibit no flow rate peak. Additionally, the enhanced flow rate can be maximized by an optimal obstacle shape, particle acceleration rate toward the hopper exit, or exit geometry of the hopper. ? 2021 American Physical Society.
Subjects
Hoppers
Velocity control
Area packings
Flow rate enhancements
Granular particles
Obstacle shapes
Optimal locations
Particle acceleration
Particle velocities
Two Dimensional (2 D)
Flow rate
acceleration
article
decomposition
flow rate
geometry
waiting room
Type
journal article