Studying the surfactant dynamics at non-isothermal liquid surface with thermography

Abstract

The dynamics of liquid multiphase systems largely depends on the conditions on the interface. The behavior of a system with adsorbed surfactant layers at the interface boundaries may differ qualitatively from the behavior of a system with pure surface. The experimental study of such systems is difficult, since the presence of adsorbed layer can most often be judged only by indirect signs. Therefore, most of the research is carried out by numerical modeling. Unfortunately, the currently existing numerical studies of liquid multiphase systems with adsorbed surfactant layer are far from perfect due to numerous simplifications and approximations assumed in theoretical models. In this paper, we propose a new approach for visualization and studying the boundary between a clean surface and an adsorbed surfactant layer. It is based on the comparison of track images of the fluid motion in the volume and the registration of the temperature distribution at the interface boundary. This approach made it possible to unambiguously associate the characteristic regions on the temperature profile with the position of the so-called stagnation point. The proposed method for visualizing the stagnation point can be useful in a number of problems of interface hydrodynamics based on the thermocapillary effect.