Modeling and simulation of two-phase flows with surfactants

The presence of surfactants, ubiquitous at most gas/liquid interfaces, has a pronounced effect on the surface tension, hence on the stress balance at the phase boundary: local variations of the capillary forces induce transport of momentum along the interface – so-called Marangoni effects. Surfactants are often soluble in one of the adjacent bulk phases, in which case there is also exchange of surfactant between the relevant bulk phase and the interface by adsorption and desorption. Along the interface surfactant is transported by convection and diffusion. Further, changes of the interfacial area due to compression or stretching cause corresponding changes in surfactant concentration.

We discuss the mathematical model governing the dynamics of such systems, including basic analytical questions and present a Volume-of-Fluid based numerical approach to compute the behaviour of fluid particles under the influence of surfactant.