Berlin 2008 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 29: Poster II

DY 29.57: Poster

Donnerstag, 28. Februar 2008, 16:00–18:00, Poster C

Fluidization of granulates wetting by liquid Helium — •Kai Huang, Masoud Sohaili, and Stephan Herminghaus — Max Planck Institute for Dynamics and Self-Organization, Goettingen

To fluidize wet granulates by vertical vibration, extra force is necessary to overcome the capillary force. We explore experimentally the fluidization of a granulate wetted by liquid Helium, because of its special liquid properties. By varying temperature around the λ point, we study how liquid Helium changes the dynamic properties of granulates. For superfluid wetting, the critical acceleration for fluidization increases almost linearly with film thickness. This indicates that superfluid starts to flow and forms liquid bridges. For wetting by normal fluid Helium, the critical acceleration shows a relatively steep increase close to saturation. Above saturation, both superfluid and normal fluid give rise to a plateau of the critical acceleration, because the capillary force depends only weakly on the volume of the bridge. The plateau value is found to vary with temperature and shows a peak around the λ point, which indicates the influence of the specific heat of liquid Helium.