Effects of Gravitational Force and Surface Orientation on the Jumping Velocity and Energy Conversion Efficiency of Coalesced Droplets

Due to potential applications in numerous fields (self-cleaning, anti-frosting, condensation enhancement, etc.), coalescence-induced droplet jumping has been investigated extensively by numerical simulations and experiments over the past decade. In this paper, the jumping dynamics of coalesced droplets on the microstructured superhydrophobic surfaces is simulated using the lattice Boltzmann model. Effects of gravity, inclined angle and droplet radius ratio on the jumping velocity and energy conversion efficiency are studied. The numerical results demonstrate that jumping droplets on inclined surfaces driven by the tangential gravity can successfully detach from the surface without returning to the original spot. The jumping velocity can be improved by a larger inclined angle. Coalescence-induced jumping of two-mismatched droplets on the horizontal surface can also produce a horizontal velocity that drives them detaching from the surface along x direction or coalescing with other droplets. Both jumping velocity and energy conversion efficiency are reduced by a lower radius ratio and a larger gravitational coefficient. In addition, no jumping behavior can be observed when energy conversion efficiency is less than 2%.