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Recirculation cells for granular flow in cylindrical rotating tumblers.
Umberto D'Ortona1, Nathalie Thomas2, Richard M Lueptow3
1Aix Marseille Univ., CNRS, Centrale Marseille, M2P2, Marseille, France.
Physical Review. E
|June 17, 2018
Summary
Secondary flows, or recirculation cells, form in rotating cylindrical tumblers. These flow patterns are influenced by tumbler geometry and impact particle mixing.
Area of Science:
- Physics of granular materials
- Fluid dynamics in granular systems
Background:
- Understanding particle flow in rotating equipment is crucial for industrial processes.
- Previous studies focused on spherical and conical tumblers, leaving cylindrical systems less explored.
Purpose of the Study:
- To investigate the velocity field and flowing layer structure in rotating cylindrical tumblers.
- To characterize the formation and behavior of secondary flows (recirculation cells).
Main Methods:
- Detailed discrete element method (DEM) simulations.
- Analysis of monodisperse particle flow in partially filled 3D cylindrical rotating tumblers.
Main Results:
- Recirculation cells develop near endwalls, with axial drift towards the endwall near the surface and towards the midlength deeper within the flowing layer.
- Oppositely oriented recirculation cells form adjacent to endwall cells.
- Endwall cell size is largely independent of tumbler length, rotation speed, and fill level (25-50%).
- Shorter tumblers show reduced or absent central cells, while longer tumblers develop stagnation zones between central cells.
Conclusions:
- Cylindrical tumbler geometry significantly influences particle flow patterns and secondary flow development.
- Endwall effects are dominant, especially in shorter tumblers.
- These findings offer insights into particle mixing and frictional effects within rotating cylindrical systems.
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