Thermocapillary migration and interaction dynamics of droplets in a constricted domain

摘要

Migration of confined droplets in a stationary fluid medium due to thermocapillary forces is considered. An in-house solver with isosurface based interface reconstruction developed in OpenFOAM has been employed to carry out numerical simulations. Thermocapillary migration of a single droplet in a constricted domain with constriction comparable to the droplet size shows that the migration velocity has non-monotonic dependence on the droplet radius. In the case of two droplets migrating in a constricted domain, the relative slowdown of a larger droplet when a smaller droplet is trailing behind reveals the possibility of interaction which is not observed in larger domains. The effects of the constricted domain size, the initial distance of separation, the radius of the trailing droplet, and the Marangoni number are analysed for this configuration. It is observed that the constriction size and Marangoni number have more influence on the interaction and dictate whether the droplets may coalesce or move with a constant separation distance. The final steady state separation distance between the droplets does not depend on the initial separation distance, but it varies with the radius of the trailing droplet. The results from the present study reveal the physical mechanisms influencing the thermocapillary migration of droplets in constricted domains and interactions between the migrating droplets. Published under license by AIP Publishing.