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DY: Dynamik und Statistische Physik
DY 43: Granular matter II
DY 43.3: Vortrag
Donnerstag, 27. März 2003, 11:45–12:00, G\"OR/229
Reversing a granular flow on a vibratory conveyor — •C. A. Krülle1, M. Rouijaa1, I. Rehberg1, R. Grochowski2, P. Walzel2, H. Elhor3, and S. J. Linz3 — 1Experimentalphysik V, Universität Bayreuth — 2Mechanische Verfahrenstechnik, Universität Dortmund — 3Theoretische Physik, Universität Münster
The controlled transport of bulk cargoes by means of vibratory conveyors is of major importance for a whole variety of industrial processes. The granular material is usually (i) agitated by a stick-slip drag on a horizontally vibrated deck with asymmetric forward and backward motions, (ii) forced to perform ballistic flights if the vertical component of the acceleration exceeds gravity, or (iii) driven by an oscillating asymmetric sawtooth-shaped profile of the base. Our system consists of an annular trough which is forced to oscillate in a circular mode, i.e. a combination of a vertical with a torsional vibration around the symmetry axis of the apparatus. For a granular material consisting of 1 mm glass beads we observe a non-monotonous dependence of the transport velocity vtr on the normalized acceleration Γ. Two maxima are separated by a regime, where the granular flow is much slower and, in a certain driving range, even reverses its direction. In contrast, a single 1 mm glass bead is propagated on this vibratory conveyor in the same direction for all accelerations. For carefully chosen excitation parameters granular surface waves can be observed, which propagate inside the trough with a constant velocity. Our main interest lies in answering the question: How does the pattern formation found in some cases influence the efficiency of the granular transport?