Numerical Study of Marangoni Convection and Mass Transport in Microdroplets

摘要

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 micro gravity condition presents an ideal case to study this phenomenon since interfacial forces are dominant over body forces. Hence Marangoni convection inside a droplet squeezed between parallel plates was studied both numerically and experimentally. The potential application of Marangoni convection at microscale includes particle separation, chaotic mixing inside the droplet and possible enhancement in liquid-liquid extraction. To explore these applications, firstly flow field inside a droplet was studied by imposing variety of surface tension gradient. Secondly a comparative numerical study of mixing inside the 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 an oil droplet rising in aqueous media was modelled to study effect of convection in liquid-liquid extraction. Finally, a biphasic system to study effect of Marangoni convection on liquid-liquid extraction was modelled.