Walking droplets & Galloping bubbles

Abstract: 

Blending experiments, simulations and theory, we will discuss two different problems motivated by fundamental questions in physics and engineering.
In the first part, we present a classical wave–particle analog of Anderson localization using  walking droplets, or “walkers”, which self-propel across a vibrating fluid bath via a resonant  interaction with their own guiding wave field. These droplets push the boundaries of classical  mechanics by exhibiting behaviors once thought to be exclusive to the quantum realm. By  investigating the erratic motion of walkers over submerged random topographies, we demonstrate the emergence of localized statistics analogous to those observed in quantum particles. Analysis of  walker trajectories reveals a suppression of diffusion when the guiding wave field extends over the disordered topography, an effect driven by a wave-mediated resonant coupling with the topography that gives rise to a confining wave potential. This hydrodynamic quantum analog illustrates how a  classical particle may localize like a wave.
In the second part, we introduce a new symmetry-breaking mechanism that enables bubbles to “gal-  lop” along horizontal surfaces in a vertically vibrated fluid chamber, propelled by a coupling  between shape oscillation modes. The resulting active bubbles exhibit a variety of trajectory regimes (rectilinear, orbital, and run-and-tumble) that can be tuned by external forcing parameters. Harnessing periodic body deformations and inertial forces, galloping bubbles achieve self-propulsion without net external forcing along their direction of motion. Proof-of-concept demonstrations illustrate the potential of this galloping motion for applications in bubble manipulation, transport, and sorting, navigation through complex fluid networks, and surface cleaning.