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DY: Fachverband Dynamik und Statistische Physik

DY 31: Granular matter / contact dynamics II

DY 31.11: Talk

Friday, March 30, 2007, 12:45–13:00, H2

Behaviour of Granular Media under Reduced Gravity — •Antje Brucks¹ and Jürgen Blum² — ¹Zentrum für angewandte Raumfahrttechnologie und Mikrogravitation, Am Fallturm, 28359 Bremen — ²Institut für Geophysik und extraterrestische Physik, Technische Universität zu Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig

Most granular surface flows are driven by gravity. Our understanding of such shear flows is much based on Earth-bound observations. Yet, pictures from Mars for example give rise to discussions on how strong the influence of ambient conditions such as air pressure and liquid lubricants in combination with reduced gravity are on the flow behaviour.

We investigated the effect of the reduction of the gravitational acceleration on the granular flow behaviour. The experiments were performed under microgravity conditions in the Bremen Drop Tower and were using a slowly rotating centrifuge for simulating low-gravity environments.

In our experiments, we used two flat (quasi-2D) sand glasses, a rotating tumbler and a somewhat larger box to resemble different aspects of flowing and avalanching granular materials as a function of g-levels between 1 g₀ and 0.01 g₀. We find that static and dynamic angle of repose increase with decreasing g-level in accordance to former investigations (Klein and White, AIAA J. 28(10),1701-1702 (1988)). However, we also find a lower limit where the cohesive properties start to dominate and prevent flow.