Instabilities of Polygonal Rings of Bouncing Droplets

Millimetric droplets bouncing on the surface of a vibrating fluid bath may interact through their shared wavefield to form bound states. In this talk, we present the results of an experimental and theoretical investigation of the stability of polygonal droplet rings. As the vibrational acceleration of the bath is increased progressively, initially stationary rings destabilize into a variety of dynamical states, often characterized by radial and azimuthal oscillations as well as transitions to more complex geometrical structures. The observed behavior is dependent on the number, size and initial separation of the drops in the ring. Extensions to the stability of droplet lattices and connections with vortex arrays in superfluid helium and Bose Einstein condensates are discussed.