Faraday waves covered by a viscoelastic sheet

TL;DR

This study investigates how viscoelastic covers affect Faraday wave behavior on a fluid surface, revealing significant impacts on dispersion, damping, and wave amplitude, with effects depending on cover thickness.

Contribution

It provides a systematic experimental analysis of hydroelastic effects on Faraday waves, highlighting the role of membrane tension and nonlinear interactions.

Findings

Wave patterns are disordered with covers compared to bare fluids.

Measured dispersion relations differ from theoretical predictions due to membrane tension.

Thin covers show damping behavior similar to bare water, influenced by boundary layer dissipation.

Abstract

The hydroelastic response of free floating viscoelastic covers is measured using Faraday waves on the surface of a vertically oscillated fluid layer. We systematically vary the thickness $d$ of the covers to investigate its effect on the hydroelastic dispersion relation, the damping and the isotropy of the waves. Compared to bare fluids, the wave patterns are disordered. Various methods are explored to define and analyze the wavelengths, the isotropy, and shape of the waves. We find a significant difference between the measurements and the theoretical dispersion relation. Over all thicknesses $d$, this is explained by an increase in the in-plane membrane tension, which scales with $d^{3/2}$. Covering waves also has a large efect on their damping. Only for thin covers ($d = 20\: \mu{\rm m}$) the onset amplitude (and thus the damping) can be explained by dissipation in the bulk and in the boundary layer of the water beneath the cover. The same was found for bare water due to the presence of an immobile surface layer. Lastly, we find a large effect of the membrane on the ampitude of the waves, which we attribute to nonlinear wave interaction.