Abstract
The present article focuses on the numerical simulation of two-dimensional (2D) binary droplet collision outcomes in an incompressible continuum gas. The Weber numbers applied to predict the various collision outcomes are within the range of those reported in the previous experiments. The droplet collision dynamics are numerically predicted by solving, separately in both phases, the unsteady 2D Navier-Stokes equations using the control volume approach on non-staggered grids. The complex topological changes of droplet interfaces are described by the level set method (LSM), which simultaneously, provides an efficient and robust way to deal automatically with breaking and merging of interfaces without any numerical constraints. The obtained results demonstrated the essential role played by the surface tension in droplet collision dynamics as a stabilising or destabilising force leading to rebound, coalescence or fragmentation collision outcomes. The mechanism of droplet disintegration at relatively high Weber number and the formation of satellite droplets are also discussed.