Spin-affected reflexive and stretching separation of off-center droplet collision

A volume-of-fluid (VOF) based numerical study on the spin-affected droplet separation of off-center collisions is presented. The roles of orbital angular momentum ${L}_{o}$ and spin angular momentum ${L}_{s}$ in affecting the droplet separation are illustrated by changing the chirality of droplet spin, showing that an augmented total angular momentum can promote the stretching separation and suppress the reflexive separation. A unified theoretical model based on conservation laws is proposed to qualitatively describe the boundaries of the coalescence-separation transition influenced by droplet self-spin motion.