Dresden 2020 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 50: Granular Matter and Granular Dynamics II
DY 50.1: Talk
Thursday, March 19, 2020, 10:00–10:15, ZEU 160
Granular Rheology from First Principles — •Till Kranz1, Olfa Lopez2, Olivier Coquand2, and Matthias Sperl2,1 — 1Institut für Theoretische Physik, Uni Köln — 2Institut für Materialphysik im Weltraum, DLR Köln
We have recently demonstrated that the Granular Integration
Through Transients (GITT) formalism allows to derive a constitutive
equation for the shear stress σ as a function of the shear rate
γ for arbitrary shear rates and high densities [1] of a
granular fluid. Here we extend the formalism to derive a constitutive
equation for the pressure p(γ). This allows us to discuss
flow curves at constant pressure and the effective friction
µ = σ/p. The phenomenological µ(I) rheology [2] relates
the friction µ to the dimensionless inertial number I. We will
discuss the relation between the GITT expressions and µ(I)
rheology. In addition, we will present experimental stress
measurements on fluidised glass beads covering several orders of
magnitude in shear rate and displaying all the rheologigcal regimes
predicted by GITT, namely, Newtonian rheology, as well as shear
thinning and shear thickening behaviour.
[1] W. T. Kranz, F. Frahsa, A. Zippelius, M. Fuchs and
M. Sperl, PRL 121, 148002 (2018); arXiv:1710.04475
[2] GDR Midi, EPJ E 14, 341 (2004)