Dresden 2017 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 39: Particulate Matter II: From microscopic interactions to collective motion (Focus session)
DY 39.4: Vortrag
Mittwoch, 22. März 2017, 16:00–16:15, ZEU 118
Flow Curves for Granular Matter at Finite Density and Shear Rate — •Till Kranz1, Fabian Frahsa2, Annette Zippelius3, Matthias Fuchs2, and Matthias Sperl1 — 1Institut für Materialphysik im Weltraum, DLR Köln — 2Theorie der Weichen Materie, Uni Konstanz — 3Institut für Theoretische Physik, Uni Göttingen
A fundamental understanding of the stress-strain relation is crucial for the rational description of granular flows in nature and industry. Experiments and simulations have shown a nontrivial rheology with a Newtonian-fluid regime at low shear rates and densities, a yield stress at high densities, and both shear thinning and shear thickening away from the linear response regime. At high shear rates the granular fluid displays Bagnold scaling. To describe all these regimes in a unified theoretical framework poses a considerable challenge.
We will discuss a recently developed integration through transients theory for the shear stress in a far from equilibrium granular fluid at high densities and finite shear rates which complements the established low-density, linear response results derived from the Boltzmann equation. We will show that with this theory we cover the full range of rheological regimes introduced above using numerical solutions of the granular mode-coupling equations and we will present kinetic expressions for the transport coefficients. In addition, we will discuss what determines the regimes and the range of validity of our approach.