Polygonal excitations of spinning and levitating droplets

TL;DR

This paper explores the shape transformations of spinning and levitating droplets, revealing polygonal excitations driven by rotation and magnetic forces, and compares experimental observations with theoretical predictions.

Contribution

It demonstrates the formation of polygonal shapes in levitated droplets and investigates their stability and symmetry, extending understanding of fluid dynamics under rotation and magnetic influence.

Findings

Polygonal shapes form at high rotation speeds.

Magnetic levitation induces non-axisymmetric droplet shapes.

Traveling waves create droplets with 3, 4, and 5-fold symmetry.

Abstract

The shape of a weightless spinning liquid droplet is governed by the balance between the surface tension and centrifugal forces. The axisymmetric shape for slow rotation becomes unstable to a non-axisymmetric distortion above a critical angular velocity, beyond which the droplet progresses through a series of 2-lobed shapes. Theory predicts the existence of a family of 3- and 4-lobed equilibrium shapes at higher angular velocity. We investigate the formation of a triangular-shaped magnetically levitated water droplet, driven to rotate by the Lorentz force on an ionic current within the droplet. We also study equatorial traveling waves which give the droplet 3, 4 and 5-fold symmetry.