Binary droplet coalescence in shear gas flow: A molecular dynamics study

• Molecular dynamics simulation is performed to study droplets in shear gas. • The gas flow field between shear gold plates is studied. • The capillary number of nanodroplet coalescence in shear flow is investigated. • The non-bonded interactions between droplets are analyzed. Molecular dynamics (MD) simulations of droplet collision and coalescence in shear gas flow between gold plates were presented. The shear velocity, normal symmetry velocity and splitting phenomenon of gas were studied through the statistical analysis of gas molecular velocities. The normal symmetric velocity is the average velocity of the gas molecules moving symmetrically away from the plates in the normal direction. The change of adsorptive layers of gas molecules on solid plates with plate velocity was investigated by analyzing the density distribution of gas molecules. Capillary number and initial offset are the main parameters affecting droplet coalescence. By changing these two parameters, three main droplet collision results were obtained: coalescence, temporary bridge formation and sliding. The non-bonded interactions between droplets in various collision results were investigated and it was found that they can well correspond to the interface change processes. The regime diagrams were established to study the relationship between different results and parameters. Our study provides a new idea for further understanding of droplet coalescence in gas shear flow.