Granular Brownian ratchet model.
We show by numerical simulations that a nonrotationally symmetric body, whose orientation is fixed and whose center of mass can slide along a rectilinear guide, under the effect of inelastic collisions with a surrounding gas of particles, displays directed motion. We present a theory which explains how the lack of time reversal induced by the inelasticity of collisions can be exploited to generate a steady average drift. In the limit of a heavy ratchet, we derive an effective Langevin equation whose parameters depend on the microscopic properties of the system and obtain a fairly good quantitative agreement between the theoretical predictions and simulations concerning effective friction, diffusivity, and average velocity.
Università di Camerino, Dipartimento di Fisica, Via Madonna delle Carceri, I-62032 Camerino, Italy.
Giulio
G
Costantini
Umberto
U
Marini Bettolo Marconi
Andrea
A
Puglisi