The stability of evaporating binary liquid film heated from below*

In this work we consider the evaporation of a thin liquid layer which consists of a binary mixture of volatile liquids. The mixture is on top of a heated substrate and in contact with the gas phase that consists of the same vapour of the binary mixtures. The effect of vapour recoil, thermo- and soluto-capillarity and the van der Waals interactions are considered. We derive the long-wave evolution equations for the free interface and the concentration that govern the two-dimensional stability of the layer subject to the above coupled mechanisms and perform a linear stability analysis. The developed linear theory describes two modes of instabilities, a monotonic instability mode and an oscillatory instability mode. By means of transient simulations we analyse how these instabilities depend on the destabilising effects considered. More precisely we discuss how the solutal Marangoni effect defines the mode of  instability that develops during the evaporation of the liquid layer due to preferential evaporation of one of the components.