Flow development at the surfaces of bubbles and droplets in gradient solutions of a surfase-active liquid

The development of solutocapillary flows at the surfaces of air bubbles and chlorobenzene droplets was experimentally studied in nonuniform aqueous solutions of ethanol and isopropanol, which have a low surface tension and, hence, exhibit surface-active properties with respect to water. The experiments demonstrated the retardation of the onset of the development of the Marangoni concentration-induced convection relative to the moment of the contact between an inflowing surfactant (alcohol) and the surface. The critical concentration gradients (the Marangoni diffusion numbers) necessary for the initiation of mass transfer of a liquid along the interface were determined as dependent on the rate of inflow of a tongue of a more concentrated solution and the initial alcohol concentration around the bubble.