Thermocapillary instability and rivulet structure formation in uniformly heated falling liquid film

A system of equations is derived to describe the nonstationary three-dimensional flow of non-isothermal liquid film in the presence of thermocapillary effect in long-wave approximation. The developed model is applicable for moderate Reynolds numbers and does not imply an a priori temperature profile in the film. Based on the derived equations the stability of a uniformly heated vertically falling liquid film is considered relative to spanwise perturbations. The linear analysis of the flow stability is carried out, and the dispersion dependences are obtained. A numerical method is used to study the nonlinear development of instabilities in 2D and 3D statements. It is shown that in a 3D statement, a small transverse perturbation evolves into the time-independent rivulet structure. The influence of dimensionless criteria of the problem on characteristic time and spatial scales of instability development and parameters of rivulet structures has been revealed.