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DY: Dynamik und Statistische Physik

DY 25: Granuar Matter and Contact Dynamics I

DY 25.6: Vortrag

Dienstag, 28. März 2006, 15:45–16:00, SCH 251

Behaviour of Granular Flow under Variable Gravitational Level — •Antje Brucks¹, Tim Arndt¹, and Richard M. Lueptow² — ¹Zentrum f. angew. Raumfahrttechnologie u. Mikrogravitation, Universität Bremen, Am Fallturm, 28357 Bremen — ²Department of Mechanical Engineering, Northwestern University, Evanston, IL 60208, USA

While gravity drives most granular shear flows including geologic situations (landslides and sandpiles on a beach) as well as in industrial applications (processing of food and pharmaceuticals), the effect of changing the gravitational acceleration is largely unexplored. Hence, our understanding of gravity-driven granular flows is based almost exclusively on experiments under Earth’s gravity, with one exception (AIAA J. 28(10),1701-1702 (1988)). We explore the behaviour of the flowing shear layer flow in a tumbler of radius r rotating at ω and the underlying creeping motion subsurface flow over a range of g-levels from 1g to 25g. We show that the dynamic angle of repose, or slope, of the flowing shear layer is properly characterized by the Froude number, Fr=ω² r/g, when the gravitational acceleration g is varied over several orders of magnitudes of the Froude number in a large centrifuge. However, the flowing layer thickness is essentially independent of the g-level for identical Froude numbers, suggesting that the shear rate in the flowing layer must increase with increasing g-level.