Molecular Dynamics Study on Regimes of Head-on Droplet Collision

The head-on collision of two water droplets with a diameter of 10 nm in an atmospheric environment was investigated via molecular dynamics simulations. The gas molecules between droplets were visualized, and the phenomena of gas extrusion and gas molecules being captured were found. By observing and analyzing the holes regime, a "periphery-sucking" mechanism was proposed to explain the thinning in the middle of the expanding disk and the holes appearing. It was found that the splattering regime can be divided into the limited splattering regime and the divergent splattering regime. The splattering modes and droplet characteristics of the two regimes are markedly different. The non-bonded interactions and intermolecular hydrogen bond were analyzed, and it was found that increasing the Weber number (We) can effectively promote the mixing of the two droplets, promote the formation of an intermolecular hydrogen bond between the two droplets, and reduce the average lifetime of the intermolecular hydrogen bond. The radial distribution function between the water molecules was plotted, showing that increasing the We makes the water molecules more dispersed as a whole in the collision process.