Abstract
We use previous results from discrete element simulations of simple shear flows of
rigid, identical spheres in the collisional regime to show that the volume fractiondependence
of the stresses is singular at the shear rigidity. Here, we identify the shear
rigidity, which is a decreasing function of the interparticle friction, as the maximum
volume fraction beyond which a random collisional assembly of grains cannot be
sheared without developing force chains that span the entire domain. In the framework
of extended kinetic theory, i.e., kinetic theory that accounts for the decreasing in
the collisional dissipation due to the breaking of molecular chaos at volume fractions
larger than 0.49, we also show that the volume fraction-dependence of the correlation
length (measure of the velocity correlation) is singular at random close packing,
independent of the interparticle friction. The difference in the singularities ensures
that the ratio of the shear stress to the pressure at shear rigidity is different from zero
even in the case of frictionless spheres: we identify that with the yield stress ratio
of granular materials, and we show that the theoretical predictions, once the different
singularities are inserted into the functions of extended kinetic theory, are in excellent
agreement with the results of numerical simulations.
Original language | English |
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Article number | 013302 |
Pages (from-to) | 1-7 |
Number of pages | 7 |
Journal | Physics of fluids |
Volume | 27 |
Issue number | 013302 |
DOIs | |
Publication status | Published - 7 Jan 2015 |
Keywords
- METIS-314839
- IR-99065