Formation of cylindrical shells via sphere packing from fluidized beds

Area of Science:

• Fluid dynamics
• Granular physics
• Computational physics

Background:

• Fluidized beds are complex systems with particle interactions.
• Spontaneous particle settling along walls in narrow pipes is an observed phenomenon.
• Understanding these structures is crucial for industrial applications.

Purpose of the Study:

• To numerically investigate particle behavior in fluidized beds within narrow pipes.
• To analyze the formation and stability of particulate shells along the pipe wall.
• To explore the influence of polydispersity and friction on shell structure.

Main Methods:

• Numerical simulations of spherical particles in a vertical cylindrical pipe.
• Analysis of fluid-particle, particle-particle, and particle-wall interactions.
• Investigation of shell structure by unwrapping and analyzing particle contact points.

Main Results:

• Particles form stable, crystal-like shells along the pipe wall under specific conditions.
• Shell formation is negatively impacted by particle size polydispersity.
• A hexagonal lattice structure was observed in the shells, with defect density increasing with polydispersity.
• High particle-particle friction is necessary for shell stability in bidisperse beds.

Conclusions:

• Particulate shell formation in fluidized beds is sensitive to particle properties like polydispersity and friction.
• Polydispersity can destabilize the crystal-like shell structure.
• Particle-particle forces play a dominant role in sustaining the cylindrical shell.