Effect of thin film on the generation of vorticity by surface waves

TL;DR

This paper investigates how a thin film on a liquid surface amplifies vorticity generated by surface waves, with implications for environmental and fluid dynamics applications.

Contribution

It extends the theoretical understanding of vorticity generation by showing the effect of a monomolecular film on vorticity magnitude and its dependence on viscosity.

Findings

Vorticity is parametrically larger with a thin film than with a clean surface.

Vorticity depends on the viscosity of the liquid when a thin film is present.

Results are applicable to pollutant diffusion and vorticity reconstruction techniques.

Abstract

Recently a theoretical scheme explaining the vorticity generation by surface waves in liquids was developed [S. Filatov et al., Phys. Rev. Lett. 116, 054501 (2016)]. Here we study how a thin (monomolecular) film presented at the surface of liquid affects the generated vorticity. We demonstrate that the vorticity becomes parametrically larger than for the case with a clean surface and now it depends on viscosity of the liquid. We also discuss the motion of particles passively advected by the generated surface flow. The results can be used in different applications: from the analysis of pollutants' diffusion on the ocean surface till the reconstruction of vorticity based on the particle image velocimetry (PIV) measurements.