Fig. 3: Droplet coalescence model.
From: Droplet attraction and coalescence mechanism on textured oil-impregnated surfaces
a Schematic of coalescing droplets. The oil between the two droplets needs to be drained before coalescence. b Magnified view of the mid-section of coalescing droplets showing the flat wall that forms between them. c Cross-sectional view A-A of the mid-section of the wetting ridge. The oil is drained radially outwards with velocity \({u}_{r}\). d Time-lapse images of coalescing droplets. High pressure (convex meniscus indicated by arrow) builds up in the wetting ridge after the first peak. e The experimental time-lag (\({\triangle}{t}\)) agrees with the theoretical prediction (\({{\triangle}t}_{{{\mathrm{model}}}}\)) that is obtained by approximating the oil drainage as a flow between two parallel plates (Poiseuille flow).
