Universal wrinkling dynamics of a sheet on viscous liquid

TL;DR

This study explores how a thin elastic sheet's wrinkling behavior on a viscous liquid is governed by deformation speed, revealing dynamic wavelength selection and coarsening, with a theoretical model applicable to various viscous-elastic systems.

Contribution

It introduces a dynamic model coupling viscous flow and elastic bending to predict wrinkle wavelength selection and coarsening in real-time, extending static laws to dynamic conditions.

Findings

Deformation speed controls initial wrinkle wavelength.

Wrinkles coarsen after active compression stops.

Model accurately predicts wavelength dynamics in experiments.

Abstract

We investigate the wrinkling dynamics of a thin elastic sheet that is indented or compressed while floating on a viscous liquid. We show that the deformation speed controls the dynamics, leading to a wrinkle wavelength significantly smaller than that selected under quasistatic compression. Once active compression ceases, the wrinkles coarsen until their wavelength relaxes toward the equilibrium value. We develop a theoretical model coupling Stokes flow in the liquid to elastic bending of the sheet, which quantitatively predicts both the initial wavelength selection and its subsequent coarsening. We demonstrate that the same mechanism governs two dimensional and axisymmetric geometries, thereby extending classical static wavelength selection laws to dynamic situations. Although developed from controlled laboratory experiments, the model captures a generic viscous-elastic coupling and applies broadly to thin elastic films interacting with viscous environments, including the formation of surface wrinkles in pahoehoe lava flows.