Volume of Fluid simulations of surfactant-laden interfaces

Flowing systems characterized by the presence of fluid-fluid interfaces are commonly found in nature and in a large number of industrial processes. These flows are often characterized by the presence of surface-active agents, also known as surfactants, which influence the formation, growth, breakage, coalescence and dynamics of the interface separating the different fluid phases. The term surfactant encompasses molecules and particles that naturally collect at the interface and locally reduce surface tension according to their concentration. Local modifications of the surface tension value introduce complex interfacial dynamics: (i) the deformability of the interface changes according to the local surfactant concentration, (ii) Marangoni stresses are generated, proportional to the surface tension gradients and acting along the interface. We propose a numerical method to describe the dynamics of surfactant over moving and deforming interfaces, which can also undergo breakage and coalescence; the dynamics of the interface is simulated using an algebraic volume of fluid method. Several test cases and benchmarks will also be presented to show the performances of the proposed method.