Mechanisms leading to axial segregation of bidisperse particles in rotating tumblers
Abstract
The origin of segregated axial bands for size-bidisperse particles in long rotating tumblers is a long-standing question in granular flows and a problem of both fundamental and practical interest. Using DEM simulations, we consider the streamwise and time-dependent development of the underlying instability as well as performing a broad parametric study over a wide range of particle size ratios, tumbler lengths and diameters, species fractions, and fill levels to determine the conditions under which axially segregated bands appear. We show that initial radial segregation of the small and large particles in the surface flowing layer results in a layer of mixed particles with a higher bulk density due to more efficient packing over a layer of nearly monodisperse small particles with a lower bulk density. This leads to a granular Rayleigh-Taylor-like instability that produces recirculation cells driving axial band formation. The appearance of a layer of high-density mixed particles over a layer of lower-density monodisperse particles can be directly connected to the operating conditions, explaining why axially segregated bands appear only under certain conditions. Typically, increasing the particle size ratio improves packing and increases the density of the mixed layer, enhancing the Rayleigh-Taylor instability and accelerating axial segregation.
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BibTeX
@article{dortona2026mechanisms,
title = {{Mechanisms leading to axial segregation of bidisperse particles in rotating tumblers}},
author = {Umberto d'Ortona and Richard Lueptow and Nathalie Thomas},
journal = {Physical Review E},
year = {2026},
month = sep,
doi = {10.1103/d6jy-d5h7},
eprint = {2610.18885},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05775505v1},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - Mechanisms leading to axial segregation of bidisperse particles in rotating tumblers
AU - Umberto d'Ortona
AU - Richard Lueptow
AU - Nathalie Thomas
PY - 2026
DA - 2026/09/01
JO - Physical Review E
DO - 10.1103/d6jy-d5h7
UR - https://hal.science/hal-05775505v1
AB - The origin of segregated axial bands for size-bidisperse particles in long rotating tumblers is a long-standing question in granular flows and a problem of both fundamental and practical interest. Using DEM simulations, we consider the streamwise and time-dependent development of the underlying instability as well as performing a broad parametric study over a wide range of particle size ratios, tumbler lengths and diameters, species fractions, and fill levels to determine the conditions under which axially segregated bands appear. We show that initial radial segregation of the small and large particles in the surface flowing layer results in a layer of mixed particles with a higher bulk density due to more efficient packing over a layer of nearly monodisperse small particles with a lower bulk density. This leads to a granular Rayleigh-Taylor-like instability that produces recirculation cells driving axial band formation. The appearance of a layer of high-density mixed particles over a layer of lower-density monodisperse particles can be directly connected to the operating conditions, explaining why axially segregated bands appear only under certain conditions. Typically, increasing the particle size ratio improves packing and increases the density of the mixed layer, enhancing the Rayleigh-Taylor instability and accelerating axial segregation.
SN - 2470-0045
SN - 2470-0053
ER -