Experimental study of Marangoni bubble migration in normal gravity

Abstract

Marangoni convection, whether thermal or solutal, is known to have a profound impact on many technological processes involving gas inclusions in a liquid phase. Evidently, similar phenomena may arise both in thermocapillary and solutocapillary situations, due to similarity of the motion driving mechanisms. However, the fact that the characteristic times of heat and surfactant diffusion generally differ by several orders of magnitude lends singularity to the behavior of Marangoni convection in inhomogeneous mixtures. Moreover, in the solutocapillary case one can meet the action of some additional effects associated with dissolution of the surfactant in a liquid, its adsorption at the interface and evaporation into a gas phase. This paper presents a comparative analysis of the results of ground experiments studying the behavior of air bubbles in a liquid under the action of thermocapillary and solutocapillary forces. The use of original experimental techniques makes it possible to eliminate the influence of gravity effects. A new Marangoni phenomenon—solutocapillary bubble migration—was detected and investigated. The results of studying thermal and concentration convective flows and bubble motion, in relation to bubble size, time, liquid layer thickness and fluids properties, are presented and discussed.