Bouncing droplets on a billiard table

TL;DR

This paper develops a dynamical systems model to analyze bouncing and walking droplets on an oscillating fluid surface, exploring bifurcations, stability, and chaotic behaviors in a billiard table domain.

Contribution

It introduces a novel iterative map model for droplet dynamics on oscillating baths, detailing conditions for stable walking and chaotic bouncing, and analyzing trajectories in a billiard domain.

Findings

Bifurcation from bouncing to walking identified.

Stable walking states depend on surface wave properties.

Trajectories vary from dense curves to chaotic paths as parameters change.

Abstract

In a set of experiments, Couder et. al. demonstrate that an oscillating fluid bed may propagate a bouncing droplet through the guidance of the surface waves. We present a dynamical systems model, in the form of an iterative map, for a droplet on an oscillating bath. We examine the droplet bifurcation from bouncing to walking, and prescribe general requirements for the surface wave to support stable walking states. We show that in addition to walking, there is a region of large forcing that may support the chaotic bouncing of the droplet. Using the map, we then investigate the droplet trajectories for two different wave responses in a square (billiard ball) domain. We show that for waves which are quickly damped in space, the long time trajectories in a square domain are either non-periodic dense curves, or approach a quasiperiodic orbit. In contrast, for waves which extend over many wavelengths, at low forcing, trajectories tend to approach an array of circular attracting sets. As the forcing increases, the attracting sets break down and the droplet travels throughout space.