NUMERICAL STUDY OF MARANGONI CONVECTION AND MASS TRANSPORT IN MICRODROPLETS

Abstract

Marangoni convection is a flow resulting from a surface tension gradient at air/liquid interface caused by temperature gradient, concentration of surfactant or applied electric field. Marangoni convection when caused by temperature gradient is also known as thermo-capillary effect. A microgravity condition presents an ideal case to study this phenomenon, since interfacial forces are dominant over body forces. Hence Marangoni convection inside the micro-droplet was studied both numerically and experimentally. The potential application at micro-scale includes particle separation, chaotic mixing inside the droplet and possible enhancement in liquid liquid extraction. To explore these application, firstly flow field inside a droplet was studied by imposing variety of surface tension gradient. Secondly a comparative numerical study of mixing inside a droplet was done for pure diffusive and convective diffusive mixing cases, to evaluate the efficiency of Marangoni convection in mixing. Next, a biphasic system of oil droplet rising in an aqueous phase was modeled to study effect of convection on liquid liquid extraction. Finally a biphasic system to study effect of Marangoni convection on liquid liquid extraction was modeled.