Harris, D. M., & Bush, J. W. (2014). Droplets walking in a rotating frame: from quantized orbits to multimodal statistics. Journal of Fluid Mechanics, 739, 444-464.
We present the results of an experimental investigation of a droplet walking on the
surface of a vibrating rotating fluid bath. Particular attention is given to demonstrating
that the stable quantized orbits reported by Fort et al. (Proc. Natl Acad. Sci.,
vol. 107, 2010, pp. 17515–17520) arise only for a finite range of vibrational
forcing, above which complex trajectories with multimodal statistics arise. We first
present a detailed characterization of the emergence of orbital quantization, and
then examine the system behaviour at higher driving amplitudes. As the vibrational
forcing is increased progressively, stable circular orbits are succeeded by wobbling
orbits with, in turn, stationary and drifting orbital centres. Subsequently, there is a
transition to wobble-and-leap dynamics, in which wobbling of increasing amplitude
about a stationary centre is punctuated by the orbital centre leaping approximately
half a Faraday wavelength. Finally, in the limit of high vibrational forcing, irregular
trajectories emerge, characterized by a multimodal probability distribution that reflects
the persistent dynamic influence of the unstable orbital states.