Interface roughness effect on slow cyclic annular shear of granular materials

Koval, Georg; Chevoir, François; Roux, Jean‐Noël; Sulem, Jean; Corfdir, Alain

doi:10.1007/s10035-011-0267-2

Cited by 38 publications

(10 citation statements)

References 33 publications

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“…Koval et al [78,79] shows a sharp increase of the apparent friction coefficient at the wall when increasing the roughness above 0.4 then a saturation. Moreover, the slip velocity increases when decreasing the roughness, in agreement with previous results [73].…”

Section: Rough Bottom Surfacesmentioning

confidence: 99%

Rheological properties of dense granular flows

Jop

2015

Comptes Rendus. Physique

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Section: Rough Bottom Surfacesmentioning

confidence: 99%

Rheological properties of dense granular flows

Jop

2015

Comptes Rendus. Physique

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“…The size polydispersity ensures that the flow profiles near the walls are not influenced by the ordering of grains [9,22]. While the bulk and boundary beads are always chosen of the same material, their size ratio δ=d wall /d bulk was varied in order to investigate the impact of the relative boundary roughness η which is defined by the normalized penetration of the flowing particles into the rough surface as η=1+δ− 1+2δ−δ 2 /3 [23,24]. For smooth walls η=0.…”

mentioning

confidence: 99%

Coexistence and Transition between Shear Zones in Slow Granular Flows

et al. 2013

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We report experiments on slow granular flows in a split-bottom Couette cell that show novel strain localization features. Nontrivial flow profiles have been observed which are shown to be the consequence of simultaneous formation of shear zones in the bulk and at the boundaries. The fluctuating band model based on a minimization principle can be fitted to the experiments over a large variation of morphology and filling height with one single fit parameter, the relative friction coefficient μ(rel) between wall and bulk. The possibility of multiple shear zone formation is controlled by μ(rel). Moreover, we observe that the symmetry of an initial state, with coexisting shear zones at both side walls, breaks spontaneously below a threshold value of the shear velocity. A dynamical transition between two asymmetric flow states happens over a characteristic time scale which depends on the shear strength.

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“…The link of this macroscopic approach with the microscopic scale of the wall roughness compared to the particle size has been clarified experimentally by Koval et al (2011), in an annular configuration, by using wellcontrolled groove shapes on a shearing cylinder. It is shown that above some threshold of a properly defined dimensionless rugosity, the apparent wall friction coefficient undergoes a sharp transition and reaches approximately the internal coefficient of friction of the material, which justifies the present definition of rough walls.…”

Section: Boundary Condition At the Lateral Wallsmentioning

confidence: 99%

Depth and minimal slope for surface flows of cohesive granular materials on inclined channels

Ryck

Louisnard

2013

J. Fluid Mech.

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We present analytical predictions of the depth and onset slope of the steady surface flow of a cohesive granular material in an inclined channel. The rheology of Jop, Forterre & Pouliquen (Nature, vol. 441, 2006, pp. 727-730) is used, assuming co-axiality between the stress and strain-rate tensors, and a coefficient of friction dependent on the strain rate through the dimensionless inertial number I. This rheological law is augmented by a constant stress representing cohesion. Our analysis does not rely on a precise µ(I) functional, but only on its asymptotic power law in the limit of vanishing strain rates. Assuming a unidirectional flow, the Navier-Stokes equations can be solved explicitly to yield parametric equations of the iso-velocity lines in the plane perpendicular to the flow. Two types of channel walls are considered: rough and smooth, depicting walls whose friction coefficient is respectively larger or smaller than that of the flowing material. The steady flow starts above a critical onset angle and consists of a sheared zone confined between a surface plug flow and a deep dead zone. The details of the flow are discussed, depending on dimensionless parameters relating the static friction coefficient, cohesion strength of the material, incline angle, wall friction, and channel width. The depths of the flow at the centre of the channel and at the walls are calculated by a force balance on the flowing material. The critical angle for the onset of the flow is also calculated, and is found to be strongly dependent on the channel width, in agreement with experimental results on heap stability and in rotating drums. Our results predict the important conclusion that a cohesive material always starts to flow for an incline angle lower than 90 • between smooth walls, whereas in a narrow enough channel with rough walls, it may not flow, even if the channel is inclined vertically.

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Interface roughness effect on slow cyclic annular shear of granular materials

Cited by 38 publications

References 33 publications

Rheological properties of dense granular flows

Rheological properties of dense granular flows

Coexistence and Transition between Shear Zones in Slow Granular Flows

Depth and minimal slope for surface flows of cohesive granular materials on inclined channels

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