Wed October 26th 2011
Seminar A granular ratchet: Spontaneous symmetry breaking and fluctuation theorems in a granular gas
Devaraj van der Meer


We construct a ratchet of the Smoluchowski-Feynman type, consisting of four
vanes that are allowed to rotate freely in a vibrofluidized granular gas. The necessary out-of-equilibrium environment is provided by the inelastically colliding grains, and the equally crucial symmetry breaking by applying a soft coating to one side of each vane. The onset of the ratchet effect occurs at a critical shaking strength via a smooth, continuous phase transition. For very strong shaking the vanes interact actively with the gas and a convection roll develops, sustaining the rotation of the vanes. From the experimental results we show that a steady state fluctuation relation holds for the work injected to the system, and that its entropy production satisfies a detailed fluctuation theorem. Surprisingly, we find that the above relations are satisfied even when a convection roll has developed and there exists a strong coupling between the motion of the vanes and the granular gas.
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The 10th Complex Motion in Fluids 2021
Max Planck Gesellschaft
Centre for Scientific Computing