Dresden 2009 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 20: Focused Session: Pattern formation in colloidal and granular systems

DY 20.3: Topical Talk

Donnerstag, 26. März 2009, 10:30–11:00, HÜL 386

Beyond Faraday's crispations: nonlinear patterns of shaken granular material — •Christof Kruelle — Maschinenbau und Mechatronik, Hochschule Karlsruhe - Technik und Wirtschaft

When granular material is shaken both in horizontal and vertical direction simultaneously, as commonly done in vibratory conveyors that are well established in routine industrial production for controlled transport of bulk solids, the transported goods can exhibit a surprisingly large variety of surface patterns. For example, if a monolayer of glass beads is vibrated in a circularly manner in a narrow annular channel, a coexistence of a solidlike and a gaslike domain can be observed. The solid fraction decreases with increasing acceleration and shows hysteresis. The sharp boundaries between the two regions travel around the channel faster than the particles are transported. By using a molecular dynamics simulation we were able to extract the local granular temperature and number density. It was found that the number density in the solid phase is several times that in the gas, while the temperature is orders of magnitude lower.

If the number of particles is increased further, localized period-doubling waves arise. These solitary wave packets are accompanied by a locally increased particle density. The width and velocity of the granular wave pulses are measured as a function of the bed height. A continuum model for the material distribution, based on the measured granular transport velocity as a function of the bed thickness, captures the essence of the experimental findings.