title: Experimental realization of a rotational ratchet in a granular gas.
abstract: 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.
authors.affiliation: Physics of Fluids, University of Twente, Post Office Box 217, 7500 AE Enschede, The Netherlands.
authors.forename: Peter
authors.initials: P
authors.lastname: Eshuis
authors.forename: Ko
authors.initials: K
authors.lastname: van der Weele
authors.forename: Detlef
authors.initials: D
authors.lastname: Lohse
authors.forename: Devaraj
authors.initials: D
authors.lastname: van der Meer