Certain peculiarities of the solutocapillary convection

This paper presents experimental results on solutocapillary Marangoni convection, an effect that occurs in a thin horizontal layer of the inhomogeneous solution of a surface-tension-active agent (surfactant) either near the free upper boundary of the layer or near the surface of an air bubble injected into the fluid. A procedure using interferometry is developed for simultaneously visualizing convective flow structures and concentration fields. A number of new phenomena are observed, including the deformation and rupture of the liquid layer due to a surfactant droplet spread over its surface; bubble self-motion (migration) toward higher surfactant concentrations; self-sustained convective flow oscillations around stationary bubbles in a fluid vertically stratified in concentration; and the existence of a threshold for a solutal Marangoni flow in thin layers. A comparison of solutocapillary and thermo-capillary phenomena is made.