Dynamics of Free-Surface Flows With Surfactants

Abstract

There is ample quantitative evidence (through, for example, surface tension measurements) of the presence of surfactants at the air-sea interface in sufficient quantities to influence the sea surface dynamics and its interactions with ambient flow turbulence. The importance of the role of the surfactants can also be judged from independent observations of phenomena such as suppression of short wavelength capillary waves and the presence of long-lived slick structures at the ship wakes. Although there is consensus on the presence of surfactants as the underlying reason behind these phenomena, the capability of quantitative predictions is still lacking for most of them. The objective of the present work is to introduce to the general engineering mechanics community the governing equations and the relevant issues associated with the study of free surface flows with surfactants. In particular, we focus on the interactions between a high Reynolds number flow, interface deformation and surfactant distribution next to and at the water-air interface. In addition, recent progress is briefly reviewed. Then, the remaining outstanding issues to allow the understanding of the dynamics of nonlinear interactions between turbulent flow and surfactant structure and concentration at the air-water interface are outlined.