Impact of an insoluble surfactant on the thresholds of evaporative Bénard-Marangoni instability under air.

It is known that the addition of an insoluble surfactant to a Bénard-Marangoni (BM) layer heated from below or cooled from above can give rise to a supplementary, oscillatory mode of instability. Here the objective is to see how exactly this plays out in the framework of a recently studied and experimentally tested case of a non-long-wavelength BM instability driven by diffusion-limited evaporation into air in isothermal surroundings. Linear stability analysis is accomplished within a now standard reduction to a one-sided model.

Nonlinear large-scale Marangoni convection in a heated liquid layer with insoluble surfactant.

The nonlinear development of monotonic and oscillatory long-wave Marangoni instabilities in a heated horizontal layer of a liquid, containing an insoluble surfactant on its surface, is investigated. By means of asymptotic expansions, weakly nonlinear amplitude equations, which govern the evolution of disturbances near the instability threshold, are derived. It turns out that both kinds of instabilities are subcritical; therefore, the asymptotic analysis does not allow us to find any stable supercritical regimes.