First normal stress difference and crystallization in a dense sheared granular fluid

Meheboob Alam; Stefan Luding

doi:10.1063/1.1587723

paper

First normal stress difference and crystallization in a dense sheared granular fluid

arXiv:cond-mat/0306689 · doi:10.1063/1.1587723

Abstract

The first normal stress difference ( $N_{1}$ ) and the microstructure in a dense sheared granular fluid of smooth inelastic hard-disks are probed using event-driven simulations. While the anisotropy in the second moment of fluctuation velocity, which is a Burnett-order effect, is known to be the progenitor of normal stress differences in {\it dilute} granular fluids, we show here that the collisional anisotropies are responsible for the normal stress behaviour in the {\it dense} limit. As in the elastic hard-sphere fluids, $N_{1}$ remains {\it positive} (if the stress is defined in the {\it compressive} sense) for dilute and moderately dense flows, but becomes {\it negative} above a critical density, depending on the restitution coefficient. This sign-reversal of $N_{1}$ occurs due to the {\it microstructural} reorganization of the particles, which can be correlated with a preferred value of the {\it average} collision angle $θ_{a v} = π /4 \pm π /2$ in the direction opposing the shear. We also report on the shear-induced {\it crystal}-formation, signalling the onset of fluid-solid coexistence in dense granular fluids. Different approaches to take into account the normal stress differences are discussed in the framework of the relaxation-type rheological models.

21 pages, 13 figures

First normal stress difference and crystallization in a dense sheared granular fluid

Abstract

References in corpus (4)

Cited by in corpus (23)