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

SUBMITTER: Krishnaraj KP 

PROVIDER: S-EPMC4755268 | biostudies-literature | 2016 Feb

REPOSITORIES: biostudies-literature