Controlling the electrostatic Faraday instability using superposed electric fields

TL;DR

This study investigates how superimposing different electric fields influences electrostatic Faraday waves at fluid interfaces, enabling control over wave patterns and transition behaviors through experimental and theoretical analysis.

Contribution

It introduces a novel method to control Faraday wave patterns by superposing AC and DC electric fields, with experimental validation and theoretical modeling.

Findings

Wavelength can be tuned continuously with DC admixture.

Pattern wavelength exhibits jumps during harmonic to subharmonic transition.

Good agreement between experimental results and theoretical predictions.

Abstract

When the interface between a dielectric and a conducting liquid is excited by an oscillatory electric field, electrostatic Faraday waves can be induced. Here, we study the response of the interface to an AC electric field, which is superposed by either a second AC field of different frequency, or by a DC field. An algorithm based on light refraction at the fluidic interface is used to obtain the spatio-temporal response of the Faraday waves, and the critical voltage corresponding to onset of instability, the interfacial oscillation frequency and the dominant wavelengths are determined. The influence of the mixing ratio, which denotes the relative amplitudes of the different components of the driving signal, is analyzed, and the experimental results are compared with theoretical predictions. For AC/AC driving, gradual variations of the mixing ratio can induce a jump of the pattern wavelength, which is a result of the transition from harmonic to a subharmonic oscillation. For AC/DC driving, the interface oscillates either harmonically or subharmonically, and the response wavelength can be tuned continuously by adjusting the admixture of the DC component. For both driving modes, the experiments show good agreement with theory.