Volume 116, Number 1, October 2016
|Number of page(s)||7|
|Section||Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics|
|Published online||16 November 2016|
Active dry granular flows: Rheology and rigidity transitions
1 Physique et Mécanique des Milieux Hétérogènes, PMMH UMR 7636 ESPCI - CNRS - Univ. Paris-Diderot - Univ. P.M. Curie - 10 rue Vauquelin, 75005 Paris, France
2 Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile Av. Blanco Encalada 2008, Santiago, Chile
Received: 9 July 2016
Accepted: 25 October 2016
The constitutive relations of a dense granular flow composed of self-propelling frictional hard particles are investigated by means of DEM numerical simulations. We show that the rheology, which relates the dynamical friction μ and the volume fraction ϕ to the inertial number I, depends on a dimensionless number , which compares the active force to the confining pressure. Two liquid/solid transitions —in the Maxwell rigidity sense— are observed. As soon as the activity is turned on, the packing becomes an “active solid” with a mean number of particle contacts larger than the isostatic value. The quasi-static values of μ and ϕ decrease with . At a finite value of the activity , corresponding to the isostatic condition, a second “active rigidity transition” is observed beyond which the quasi-static values of the friction vanishes and the rheology becomes Newtonian. For , we provide evidence for a highly intermittent dynamics of this “active fluid”.
PACS: 47.57.Gc – Granular flow / 83.80.Fg – Granular solids / 05.65.+b – Self-organized systems
© EPLA, 2016
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