Certain peculiarities of the solutocapillary convection
K.G. Kostarev Institute of Continuous Media Mechanics, Ural Branch of the Russian Academy of Sciences, ul. akad. Koroleva 1, Perm, 614013, Russian Federation
This paper presents experimental results on the 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.