Influence of wettability and initial size on the merging dynamics of droplet within a Y-shaped bifurcating channel

Abstract

Present study numerically investigates the merging dynamics of two identical dispersed droplets within a Y-shaped bifurcating channel of rectangular cross-section. A finite element method based solver is adopted to analyze the flow dynamics within the bifurcating channel for different wall wettability conditions, initial size of the dispersed droplets and for a fixed Capillary number. The merging dynamics is described with the help of morpho-dynamic evolution along with the temporal evolution of wetted area of the droplets. It reveals that the daughter droplet generated from the mating of identical parent droplets at the bifurcating tip has the affinity to stick at the junction for hydrophilic and neutral wettability configurations of the walls, thus generating longer size droplet. On the contrary, for hydrophobic wettability of the walls, the parent droplets merge to each other bypassing the bifurcating junction while mating and subsequently entrapping of droplets takes place within the daughter droplet. Moreover, the influence of wall wettability is insignificant when the initial sizes of the parent droplets are smaller.