Dresden 2009 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 18: Granular matter / contact dynamics
DY 18.9: Vortrag
Mittwoch, 25. März 2009, 18:30–18:45, HÜL 386
Wet Discs Running Down an Inclined Plane — •Seyed Habibollah Ebrahimnazhad Rahbari, Martin Brinkmann, Juergen Vollmer, and Stephan Herminghaus — Dept. Dynamics of Complex Fluids, MPI for Dynamics and Self-Organization, D-37073 Göttingen, Germany
We present results of MD-type simulations of wet discs running down an inclined plane. In our model, particles interact via a repulsive force, when they overlap, and via a hysteretic attractive force caused by liquid bridges. A liquid bridge forms when two adjacent wet discs touch each other, and entails to an attractive hysteretic force Flb(x) due to the surface tension of the liquid. That capillary bridge ruptures when the distance between two grains exceeds a critical separation Sc and dissipates energy. We use a minimal capillary model in which Flb is assumed to be constant as the liquid bridge is stretched. The dissipation in our model is only due to the rupture events of the liquid bridges.
The systems are set up by sedimentation of the discs, and immobilization of discs touching the bottom wall. Subsequently, a tilted force is applied. We find a simple scaling expression for the fluidization transition as a function of the gravitational acceleration g, the inclination angle θ, and the rupture separation Sc. For most parameter values beyond the transition, the system settles down into to a stationary homogeneous fluidized state. However, there are also regimes where it becomes bistable or shows a thermal runaway.