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DY: Fachverband Dynamik und Statistische Physik

DY 24: Poster I

DY 24.46: Poster

Mittwoch, 28. März 2007, 16:00–18:00, Poster D

Surface Melting and Leidenfrost Effect in Wet Granular Matter — •Klaus Röller, Axel Fingerle, and Stephan Herminghaus — MPI for Dynamics and Self-Organization, Bunsenstr. 10, D-37073 Göttingen, Germany

We report two vertical phase separations occurring in wet granular matter when placed on top of a sinusoidally oscillating bottom plate. The system has been studied by means of a molecular dynamic simulation which takes the hysteretic liquid bridge force between wetted particles into account [1]. For low accelerations of the shaking bottom plate we observe a pure solid phase. At a certain value of the acceleration, the top layer starts to melt as indicated by the height dependent diffusion coefficient. As the acceleration is increased further, the height of the fluid phase floating on top of the solid phase grows until it diverges at a well defined solid to fluid transition. As we increase the acceleration further a second vertical phase separation sets in: the condensed phase hovers on top of a gas phase, quite reminiscent of the classical Leidenfrost effect. This is the first observation of density inversion in wet granular matter. The chunk above the gas is thermally isolated by the low heat conductivity of the gas in which the upward stream of injected energy is dissipated in frequent ruptures of liquid bridges. Finally, above an acceleration depending on the filling height the condensed phase evaporates completely.

[1] Advances in Physics 54, 221 (2005).