Migration of a droplet in a liquid: effect of insoluble surfactants and thermal gradient

The steady-state migration velocity of a spherical droplet placed in a second liquid is calculated taking into account gravity and several interfacial effects. The effect of insoluble surfactants at the bubble surface, surface tension gradients, surface elasticity, interfacial dilatational viscosity, interfacial diffusivity and convective and diffusive surface excess heat fluxes on the terminal velocity of the droplet are included under the assumption of small Marangoni, Reynolds and capillary numbers. This work extends earlier results, which do not take into account interfacial diffusivity.