BPCPPDYSOE21 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 13: Granular Physics 3 - organized by Matthias Sperl (Köln)
DY 13.2: Vortrag
Montag, 22. März 2021, 15:20–15:40, DYc
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); PRF 5 024305 (2020)
[2] GDR Midi, EPJ E 14, 341 (2004)