Modeling of the Marangoni instability of uniform diffusion through the interphase boundary in weightlessness conditions

In this paper, the process of surfactant diffusion through the vertical interphase boundary in the system of two immiscible liquids filling a horizontal channel was studied in a two-dimensional formulation. Densities of the base liquids were initially set equal to the surfactant density. Therefore, all subsequent changes of density in the system were caused only by the effect of contraction. At the nonunifrom diffusion, the interfacial tension is the function of the local surfactant concentration, which gives rise to the Marangoni convection. Since the system contained uncontrolled surface-active impurities, the capillary flow was initiated in a threshold manner. It was shown that at the initial stage, despite the action of the gravitational force, the Marangoni convection occurred in the form of a series of periodic, paired vortices located symmetrically about the channel axis (the same as under zero gravity). As the vertical density difference increased, the number of vortex pairs reduced to a single pair...