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

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.

SUBMITTER: Krishnaraj KP

PROVIDER: S-EPMC4755268 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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

Krishnaraj K P KP Nott Prabhu R PR

Nature communications 20160211

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 ex ...[more]

PMID: 26864086

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