3D instability of a toroidal flow in the liquid partially covered by a solid film

TL;DR

This study numerically investigates the stability of a steady radial thermocapillary flow in a cylindrical setup, revealing how surfactant films induce azimuthal vortices and flow symmetry breakdown due to convective instability.

Contribution

It demonstrates the formation of inclined vortices and flow symmetry loss caused by surfactant films in thermocapillary flows, with control over azimuthal vorticity via heat source intensity.

Findings

Radial flow symmetry breaks down due to convective instability.

Inclined volumetric vortices form under surfactant films.

Azimuthal vorticity increases with heating intensity.

Abstract

Flow structure stability of a steady radial thermocapillary flow from the local heat source in cylindrical geometry has been studied numerically. The up boundary of the liquid was partially covered by the stationary film of an insoluble surfactant, pushed to the wall of the cavity. The calculations are fulfilled on the base of interfacial hydrodynamics equations by using mathematical package Comsol Multiphysics. It is shown that the effect of a radial flow symmetry breakdown is appeared as a result of convective instability, so that the initial poloidal rotation of the liquid transforms into the azimuthal plane. The system of inclined steady volumetric vortices is formed under the film of surfactant. The inclination angle of the plane of rotation in dependence on the intensity of radial thermocapillary flow is studied. It is shown that the azimuthal vorticity can be regulated by the power of point-heat source and by free surface area. The increase of heating intensity leads to the growth of the azimuthal vorticity. Thus, the initially radially symmetric toroidal flow is divided into two parts with the origination of vortices in the azimuthal plane under the film