Coalescence of Al droplet impacting on a melt surface

Abstract The droplet falling into its bulk liquid surface is very common but complex which widely exists in nature and industry. In this case, the impact behavior is almost simultaneous with the coalescence. To deeply understand the dynamics and mechanism of this phenomenon, molecular dynamics simulations have been performed to study the characteristics of the impact coalescence process under different conditions. Results show that four coalescence behaviors, including rebound, calm coalescence, deformation and coating, are mainly determined by the impact velocity. Interestingly, a cavity is observed in the liquid bulk when the impact velocity is big enough, which can be explained by the momentum transfer. Beyond that, the mixing degree increases with Weber number and there is a critical Weber number between rebound and coalescence. The study illustrates how the temperature and impact velocity affects the coalescence behavior and provides opportunity to well understand the droplet impact process towards its melt surface.