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DY: Fachverband Dynamik und Statistische Physik
DY 21: Granular Matter / Contact Dynamics
DY 21.2: Vortrag
Mittwoch, 13. März 2013, 15:15–15:30, H47
Shear Alignment Of Shape-Anisotropic Granular Material — •Sandra Wegner1, Tamás Börzsönyi2, Ralf Stannarius1, and Balázs Szabó2 — 1Otto-von-Guericke Universität Magdeburg, Institute for Experimental Physics, D-39016 Magdeburg, Germany — 2Institute for Solid State Physics and Optics, Wigner Research Center for Physics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary
Flow of large ensembles of elongated and flat granular particles - often encountered in nature or industry - can induce pronounced alignment of the building blocks. This phenomenon is well known, e. g. in geophysics, but hardly understood quantitatively.
We explore the shear induced orientational order and alignment inside the macroscopic material using X-ray computed tomography (CT). The preferred orientation of the long axes of the particles encloses a small angle with the streamlines in the sheared region.
Our observations demonstrate that the effect of shear alignment of dry elongated particles is very similar to the well-studied case of liquid crystals, irrespectively of the completely different types of interparticle forces. Nematic continuum theory can be used to predict some features of grain alignment.
Extracting the orientations of large numbers of particles by CT image analysis enables us to calculate a local order tensor for the system. From the tensor properties we derive the average orientation, the primary and the biaxial order parameters for the stationary state and two types of transients. In addition single particle dynamics are studied.