Effect of radius ratios of two droplets on coalescence-induced self-propelled jumping

The coalescence-induced self-propelled droplet jumping behaviors on superhydrophobic surfaces have attracted extensive interest, due to a huge application potential. The coalescence and jumping of two droplets with different radius ratios are numerically simulated, and the jumping velocity is theoretically analyzed. The jumping type changes from the vertical motion to the upward rotation motion, with the decrease of radius ratio. The droplet is not able to jump when the radius ratio is smaller than 0.4. The jumping velocity reaches several peak values when the radius ratio is smaller than 0.7. The maximum jumping velocities are theoretically predicted, which is based on the law of conservation of energy. The viscous dissipation energy which should not be ignored is the main and direct source of the errors