Distribution of surfactant along the free liquid surface under the action of surface waves

摘要

Fluctuations of an insoluble surfactant monolayer along the free liquid surface induced by standing waves are considered theoretically. The energy of the fluctuating interface is assumed to be equal to the total free energy that is a function of surface tension. The dependence of the surface concentration on the surface tension is taken according to the Gibbs adsorption equation. Van der Waals forces between molecules that are present in all condensed matter systems are taken into account in the form of van der Waals energy for a thin film. The obtained theoretical result shows that the longitudinal distribution of the surfactant concentration can be expressed analytically, and that the distribution of concentration changes relative to some reference level has been found to be periodic with a period that is half of the wave period. The maximal concentration is achieved in nodal points of the wave profile.