Numerical analysis on air entrapment during a droplet impacts on a dry flat surface

When a droplet impacts on a dry flat surface, air is generally entrapped. The formation of air bubbles into the liquid during drop impact processes has drawn extensive attention. Air entrapment during droplet-surface impaction is numerical analyzed. According to numerical results, pressure difference between gas and liquid is the main reason leading to phase interface topology changes, which is the cause of trapped air film formation. Trapped air film presents contraction, coalescence and detachment after formation. Wall heat flux distribution is closely related to dynamic feature of trapped air. At the very initial stage of impaction, trapped air largely hinders heat transfer from droplet to surface. The effective of impact velocity on bubble detachment suggesting a feasible way to eliminate bubbles in droplet impact applications.