Partial jamming and non-locality in dense granular flows

Kharel, Prashidha; Rognon, Pierre

doi:10.1051/epjconf/201714003060

Cited by 4 publications

(4 citation statements)

References 34 publications

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“…Without cohesion, non-local effects develop at low inertial numbers [17,20,33,42,5]. These effects occur in heterogeneous flows, where the friction law Eq.…”

Section: Discussionmentioning

confidence: 99%

Viscosity of Cohesive Granular Flows

Macaulay¹,

Rognon²

2020

Preprint

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Cohesive granular materials such as wet sand, snow, and powders can flow like a viscous liquid. However, the elementary mechanisms of momentum transport in such athermal particulate fluids are elusive. As a result, existing models for cohesive granular viscosity remain phenomenological and debated. Here we use discrete element simulations of plane shear flows to measure the viscosity of cohesive granular materials, while tuning the intensity of inter-particle adhesion. We establish that two adhesion-related, dimensionless numbers control their viscosity. These numbers compare the force and energy required to break a bond to the characteristic stress and kinetic energy in the flow. This progresses the commonly accepted view that only one dimensionless number could control the effect of adhesion. The resulting scaling law captures strong, non-Newtonian variations in viscosity, unifying several existing viscosity models. We then directly link these variations in viscosity to adhesion-induced modifications in the flow micro-structure and contact network. This analysis reveals the existence of two modes of momentum transport, involving either grain micro-acceleration or balanced contact forces, and shows that adhesion only affects the later. This advances our understanding of rheological models for granular materials and other soft materials such as emulsions and suspensions, which may also involve inter-particle adhesive forces.

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“…Without cohesion, non-local effects develop at low inertial numbers [17,20,33,42,5]. These effects occur in heterogeneous flows, where the friction law Eq.…”

Section: Discussionmentioning

confidence: 99%

Viscosity of Cohesive Granular Flows

Macaulay¹,

Rognon²

2020

Preprint

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“…Another strongly non-local model is the recent model of Nott [65], in which the integral is a weighted spatial convolution of what the local flow-rate formula would give in the surrounding media. A strongly non-local eddy-viscosity-type model has also been written [66], in which the shear-rate has a contribution from redistribution of vorticity occurring through the geometry. The corresponding PDE approximation of this model takes a form similar to an order-parameter model [66,67].…”

Section: Integral Equation Approachesmentioning

confidence: 99%

“…A strongly non-local eddy-viscosity-type model has also been written [66], in which the shear-rate has a contribution from redistribution of vorticity occurring through the geometry. The corresponding PDE approximation of this model takes a form similar to an order-parameter model [66,67].…”

Section: Integral Equation Approachesmentioning

confidence: 99%

Non-locality in Granular Flow: Phenomenology and Modeling Approaches

Kamrin

2019

Front. Phys.

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This paper reviews the emergence of non-local flow phenomena in granular materials and discusses a range of models that have been proposed to integrate an intrinsic length-scale into granular rheology. The frameworks discussed include micro-polar modeling, kinetic theory, three particular order-parameter-based models, and strongly non-local integral-based models. An extensive commentary is included discussing the current capabilities of these existing models as well as their implementational ease, physical motivation, and breadth of predictive ability.

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“…This suggests that vortices could potentially be a microstructural origin of non-local behaviour at the continuum scale. In a different paper part of these proceedings [21], we specifically focus on this connection and propose a mechanism that allows us to derive a continuum non-local fluidity model similar to that introduced in [19] simply by considering the existence of vortices.…”

Section: Viscosity and Non-localitymentioning

confidence: 99%

How granular vortices can help understanding rheological and mixing properties of dense granular flows

et al. 2017

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Abstract. Dense granular flows exhibit fascinating kinematic patterns characterised by strong fluctuations in grain velocities. In this paper, we analyse these fluctuations and discuss their possible role on macroscopic properties such as effective viscosity, non-locality and shear-induced diffusion. The analysis is based on 2D experimental granular flows performed with the stadium shear device and DEM simulations. We first show that, when subjected to shear, grains self-organised into clusters rotating like rigid bodies. The average size of these so-called granular vortices is found to increase and diverge for lower inertial numbers, when flows decelerate and stop. We then discuss how such a microstructural entity and its associated internal length scale, possibly much larger than a grain, may be used to explain two important properties of dense granular flows: (i) the existence of shear-induced diffusion of grains characterised by a shear-rate independent diffusivity and (ii) the development of boundary layers near walls, where the viscosity is seemingly lower than the viscosity far from walls.

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Partial jamming and non-locality in dense granular flows

Cited by 4 publications

References 34 publications

Viscosity of Cohesive Granular Flows

Viscosity of Cohesive Granular Flows

Non-locality in Granular Flow: Phenomenology and Modeling Approaches

How granular vortices can help understanding rheological and mixing properties of dense granular flows

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