Crystallization and jamming in narrow fluidized beds

TL;DR

This study investigates how granular materials in narrow fluidized beds crystallize and jam under high confinement, revealing phase transition-like behaviors and the influence of grain type on structure formation.

Contribution

It provides new experimental insights into the crystallization and jamming phenomena in narrow fluidized beds, highlighting the effects of confinement and flow conditions.

Findings

Grains form lattice structures with high compactness during flow deceleration.

Jamming occurs when flow velocity slightly increases after crystallization.

Different lattice structures depend on grain type.

Abstract

A fluidized bed is basically a suspension of granular material by an ascending fluid in a tube, and it has a rich dynamics that includes clustering and pattern formation. When the ratio between the tube and grain diameters is small, different behaviors can be induced by high confinement effects. Some unexpected and curious behaviors, that we investigate in this paper, are the crystallization and jamming of grains in liquids with velocities higher than that for incipient fluidization, supposed to maintain the grains fluidized. In our experiments, performed in a vertical tube of transparent material, different grains, water velocities, resting times, and velocity decelerations were used. An analysis of the bed evolution based on image processing shows that, after a decreasing flow that reaches a velocity still higher than that for incipient fluidization, grains become organized in lattice structures of high compactness, where they are trapped though with small fluctuations. These structures are initially localized and grow along time, in a similar manner as happens in phase transitions and glass formation. After a certain time, if the liquid velocity is slightly increased, jamming occurs, with grains being completely blocked and their fluctuation disappearing. We show that different lattice structures appear depending on the grain type. Our results provide new insights into fluidization conditions, glass-like formation and jamming.