SKM 2021 – wissenschaftliches Programm

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SYAM: Symposium Amorphous materials: structure, dynamics, properties

SYAM 1: Amorphous materials: structure, dynamics, properties

SYAM 1.5: Hauptvortrag

Dienstag, 28. September 2021, 15:45–16:15, Audimax 1

Constitutive law for dense agitated granular flows: from theoretical description to rheology experiment — •Olfa D’Angelo¹ and W. Till Kranz² — ¹Inst. Materialphysik im Weltraum, DLR-Köln — ²Inst. Theoretische Physik, Uni. Köln

The variety in granular materials’ behaviour makes them fascinating materials, but also difficult to encompass into a globalised theory. Recently, Kranz et al. described granular fluids close to the glass transition using mode coupling theory, and extended this theory towards the non-linear rheology of granular fluids submitted to finite shear rates [1]. This approach allows to embrace in a single theoretical framework the variety of rheological responses observed in dense granular fluids, as it predicts and delineates rheological regimes comprising Newtonian, shear thinning, and shear thickening (Bagnoldian).

We provide the first experimental validation of this theory [2], through flow curves spanning six orders of magnitude in shear rate, over a wide range of packing fractions. As we uncover the predicted rheological regimes in an air-fluidised granular bed of glass beads, we explore the areas of uncertainties in comparing our careful measurements to the theory. Experimental results and theory compare very favourably; besides the predicted regimes, experiments reveal an additional regime at high Peclet number, where Bagnold scaling is lost.

[1] W.T. Kranz, F. Frahsa, A. Zippelius, M. Fuchs, and M. Sperl, Phys. Rev. Fluids 5, 024305 (2020).

[2] O. D’Angelo, A. Shetty, M. Sperl, and W.T. Kranz, in preparation (2021).