Comparing simulation and experiment of a 2D granular Couette shear device

Abstract

We present experiments along with molecular dynamics (MD) simulations of a two-dimensional (2D) granular material in a Couette cell undergoing slow shearing. The grains are disks confined between an inner, rotating wheel and a fixed outer ring. The simulation results are compared to experimental studies and quantitative agreement is found. Tracking the positions and orientations of individual particles allows us to obtain density distributions, velocity and particle rotation rate for the system. The key issue of this paper is to show the extent to which quantitative agreement between an experiment and MD simulations is possible. Besides many differences in model-details and the experiment, the qualitative features are nicely reproduced. We discuss the quantitative agreement/disagreement, give possible reasons, and outline further research perspectives.

The critical-state yield stress (termination locus) of adhesive powders from a single numerical experiment

“…One can simulate an inhomogeneous geometry, where static regions co-exist with dynamic, flowing zones and, respectively, high density co-exists with dilated zonesat various pressure levels. From adequate local averaging over equivalent volumes-inside which all particles behave similarly-one can obtain from a single simulation already constitutive relations in a certain parameter range, as was done systematically in two-dimensional (2D) Couette ring shear cells [9,21] and three-dimensional (3D) split-bottom ring shear cells [11,12]. The fact that the split-bottom shear cell has a free surface allows to scan a range of confining pressures between zero and σ max zz , which is due to the weight of the material and determined by the filling height.…”

Constitutive relations for the shear band evolution in granular matter under large strain

“…The behavior of granular media can be simulated with the discrete element method (DEM) (Allen and Tildesley, 1987;Lätzel et al, 2003;Luding, 2008a). As the basic ingredient, a force-displacement relation that governs the interaction between pairs of particles is defined.…”

The Effect of Friction on Wide Shear Bands

“…The behavior of granular media is simulated with the discrete element method (DEM) or molecular dynamics (MD) (Allen and Tildesley 1987;Rapaport 1995;Herrmann, Hovi, and Luding 1998;Vermeer, Diebels, Ehlers, Herrmann, Luding, and Ramm 2001;Lätzel, Luding, Herrmann, Howell, and Behringer 2003;Luding 2004b;Luding 2004c;Luding 2006a;Ries, Wolf, and Unger 2007;Luding 2008). Note that both methods are identical in spirit, however, different groups of researchers use these (and also many other) names.…”

“…An alternative is to simulate an inhomogeneous geometry where static and dynamic, flowing zones co-exist and, respectively, high density co-exists with dilated zones. From adequate local averaging over equivalent volumes -inside which all particles behave similarly -one can obtain from a single simulation already constitutive relations in a certain parameter range, as was done systematically in two-dimensional Couette ring shear cells (Lätzel, Luding, and Herrmann 2000;Lätzel, Luding, and Herrmann 2001;Lätzel, Luding, Herrmann, Howell, and Behringer 2003) and bi-axial geometries (Luding 2005b;Luding 2005a). Note that both time-and space-averaging are required to obtain a reasonable statistics.…”