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research article

Experimental investigation into segregating granular flows down chutes

Wiederseiner, Sébastien  
•
Andreini, Nicolas  
•
Épely-Chauvin, Gaël  
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2011
Physics Of Fluids

We experimentally investigated how a binary granular mixture made up of spherical glass beads size ratio of 2 behaved when flowing down a chute. Initially, the mixture was normally graded, with all the small particles on top of the coarse grains. Segregation led to a grading inversion, in which the smallest particles percolated to the bottom of the flow, while the largest rose toward the top. Because of diffusive remixing, there was no sharp separation between the small-particle and large-particle layers, but a continuous transition. Processing images taken at the sidewall, we were able to measure the evolution of the concentration and velocity profiles. These experimental profiles were used to test a recent theory developed by Gray and Chugunov J. Fluid Mech. 569, 365 2006, who derived a nonlinear advection diffusion equation that describes segregation and remixing in dense granular flows of binary mixtures. We found that this theory was able to provide a consistent description of the segregation/remixing process under steady uniform flow conditions. To obtain the correct depth-averaged concentration far downstream, it was very important to use an accurate approximation to the downstream velocity profile through the avalanche depth. The S-shaped concentration profile in the far field provided a useful way of determining what we refer to as the Péclet number for segregation, a dimensionless number that quantifies how large the segregation is compared to diffusive remixing. While the theory was able to closely match the final fully developed concentration profile far downstream, there were some discrepancies in the inversion region i.e., the region in which the mixing occurs. The reasons for this are not clear. The difficulty to set up the experiment with both well controlled initial conditions and a steady uniform bulk flow field is one of the most plausible explanations. Another interesting lead is that the flux of segregating particles, which was assumed to be a quadratic function of the concentration in small beads, takes a more complicated form.

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Type
research article
DOI
10.1063/1.3536658
Web of Science ID

WOS:000287424200025

Author(s)
Wiederseiner, Sébastien  
Andreini, Nicolas  
Épely-Chauvin, Gaël  
Moser, Gaudenz
Monnereau, Mathieu
Gray, J. M. N. T.
Ancey, Christophe  
Date Issued

2011

Published in
Physics Of Fluids
Volume

23

Issue

1

Article Number

013301

Subjects

granular flow

URL

URL

http://lhe.epfl.ch/recherche/index.php?option=com_content&view=section&layout=blog&id=2&Itemid=7&lang=fr
Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
LHE  
Available on Infoscience
January 31, 2011
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/63551
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