A MANY-BODY DISSIPATIVE PARTICLE DYNAMICS STUDY OF COALESCENCE INDUCED JUMPING
Coalescence induced jumping from solid surface at mesoscale is simulated using Many-body dissipative particle dynamics (MDPD). The geometrical evolution during the coalescence of two droplets and resulted jumping were obtained and the mechanism behind this phenomenon were also investigated. The jumping maps two equal-sized droplets and two droplets with different sizes were obtained. It is found the coalescence of two equal size droplets will lead to jumping when the contact angle is larger than the minimum threshold contact angle, which is about 160°. This minimum threshold contact angle is related to droplet size as it increases when droplet size decreases. Jumping can still happen when two droplets with different sizes merge together. The maximum volume ratio for jumping of two droplets with different sizes is 3.9. Velocity field shows how internal flow evolves during the coalescence process. There is obvious velocity change inside the droplet from the beginning of the droplet deformation to jumping. The energy conversion rate from released surface energy to kinetic energy is found about 1%. These results can greatly advance the fundamental understanding of hydrodynamics behavior of coalescence induced droplet jumping.