• DOI:10.1017/jfm.2015.544
• Corpus ID: 9944227

Conjugated liquid layers driven by the short-wavelength Bénard–Marangoni instability: experiment and numerical simulation

@article{Nejati2015ConjugatedLL,
  title={Conjugated liquid layers driven by the short-wavelength B{\'e}nard–Marangoni instability: experiment and numerical simulation},
  author={Iman Nejati and Mathias Dietzel and Steffen Hardt},
  journal={Journal of Fluid Mechanics},
  year={2015},
  volume={783},
  pages={46 - 71}
}

• I. Nejati, M. Dietzel, S. Hardt
• Published 13 October 2015
• Physics
• Journal of Fluid Mechanics

The coupled dynamics of two conjugated liquid layers of disparate thicknesses, which coat a solid substrate and are subjected to a transverse temperature gradient, is investigated. The upper liquid layer evolves under the short-wavelength Bénard–Marangoni instability, whereas the lower, much thinner film undergoes a shear-driven long-wavelength deformation. Although the lubricating film should reduce the viscous stresses acting on the up to one hundred times thicker upper layer by only 10 %, it is found that the critical Marangoni number of marginal stability may be as low as if a stress-free boundary condition were applied at the bottom of the upper layer, i.e. much lower than the classical value of 79.6 known for a single film. Furthermore, it is experimentally verified that the deformation of the liquid–liquid interface, albeit small, has a non-negligible effect on the temperature distribution along the liquid–gas interface of the upper layer. This stabilizes the hexagonal pattern symmetry towards external disturbances and indicates a two-way coupling of the different layers. The experiments also demonstrate how convection patterns formed in a liquid film can be used to pattern a second conjugated film. The experimental findings are verified by a numerical model of the coupled layers.