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Shear-induced diffusion in cohesive granular flows: effect of enduring clusters

Published online by Cambridge University Press:  08 November 2018

Matthew Macaulay*
Affiliation:
Particles and Grains Laboratory, School of Civil Engineering, The University of Sydney, Sydney, NSW 2006, Australia
Pierre Rognon
Affiliation:
Particles and Grains Laboratory, School of Civil Engineering, The University of Sydney, Sydney, NSW 2006, Australia
*
Email address for correspondence: [email protected]

Abstract

We investigate the effect of intergranular cohesive forces on the properties of self-diffusion in dense granular flows. The study is based on a series of simulated plane shear flows at different inertial and cohesion numbers, in which transverse diffusivities are measured. Results evidence an increase in diffusivity by up to two orders of magnitude when introducing cohesion. This strong effect is analysed using the Green–Kubo framework, expressing the diffusivity in terms of instantaneous grain velocity fluctuations and their time correlation. This analysis shows that cohesion, by forming enduring clusters in the flow, enhances the velocity fluctuations and their time persistence, which both contribute to enhancing grain mixing and self-diffusion.

Type
JFM Rapids
Copyright
© 2018 Cambridge University Press 

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Macaulay and Rognon supplementary movie 1

Shear induced diffusion at high inertial number and without cohesion (I = 0.3 and C=0) . Grains initially at the centre of the shear cell are coloured in red, while other grains are coloured in blue. All grains keep their colour during shear.

Download Macaulay and Rognon supplementary movie 1(Video)
Video 9.8 MB

Macaulay and Rognon supplementary movie 2

Shear induced diffusion at high inertial number and with cohesion (I = 0.3 and C=25) . Grains initially at the centre of the shear cell are coloured in red, while other grains are coloured in blue. All grains keep their colour during shear.

Download Macaulay and Rognon supplementary movie 2(Video)
Video 9.8 MB

Macaulay and Rognon supplementary movie 3

Shear induced diffusion at low inertial number and without cohesion (I = 0.01 and C=0) . Grains initially at the centre of the shear cell are coloured in red, while other grains are coloured in blue. All grains keep their colour during shear.

Download Macaulay and Rognon supplementary movie 3(Video)
Video 9.8 MB

Macaulay and Rognon supplementary movie 4

Shear induced diffusion at low inertial number and with cohesion (I = 0.01 and C=25) . Grains initially at the centre of the shear cell are coloured in red, while other grains are coloured in blue. All grains keep their colour during shear.

Download Macaulay and Rognon supplementary movie 4(Video)
Video 9.6 MB