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A dilation-driven vortex flow in sheared granular materials explains a rheometric anomaly

Krishnaraj, KP and Nott, Prabhu R (2016) A dilation-driven vortex flow in sheared granular materials explains a rheometric anomaly. In: NATURE COMMUNICATIONS, 7 .

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Official URL: http://dx.doi.org/10.1038/ncomms10630

Abstract

Granular flows occur widely in nature and industry, yet a continuum description that captures their important features is yet not at hand. Recent experiments on granular materials sheared in a cylindrical Couette device revealed a puzzling anomaly, wherein all components of the stress rise nearly exponentially with depth. Here we show, using particle dynamics simulations and imaging experiments, that the stress anomaly arises from a remarkable vortex flow. For the entire range of fill heights explored, we observe a single toroidal vortex that spans the entire Couette cell and whose sense is opposite to the uppermost Taylor vortex in a fluid. We show that the vortex is driven by a combination of shear-induced dilation, a phenomenon that has no analogue in fluids, and gravity flow. Dilatancy is an important feature of granular mechanics, but not adequately incorporated in existing models.

Item Type: Journal Article
Additional Information: Copy right for this article belongs to the NATURE PUBLISHING GROUP, MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND
Department/Centre: Division of Mechanical Sciences > Chemical Engineering
Depositing User: Id for Latest eprints
Date Deposited: 02 Apr 2016 07:25
Last Modified: 02 Apr 2016 07:25
URI: http://eprints.iisc.ac.in/id/eprint/53560

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