Exotic orbits of two interacting wave sources

Abstract

As shown recently, it is possible to create, on a vibrating fluid interface, mobile emitters of Faraday waves [Y. Couder, S. Protière, E. Fort, and A. Boudaoud, Nature 437, 208 (2005)]. They are formed of droplets bouncing at a subharmonic frequency which couple to the surface waves they emit. The droplet and its wave form a spontaneously propagative structure called a "walker." In the present paper we investigate the large variety of orbital motions exhibited by two interacting walkers having different sizes and velocities. The various resulting orbits which can be circular, oscillating, epicycloidal, or "paired walkers" are defined and characterized. They are shown to result from the wave-mediated interaction of walkers. Their relation to the orbits of other localized dissipative structures is discussed.