Simulation of coalescence dynamics of droplets on surfaces with different wettabilities

The head-on-collision coalescence dynamics for droplets on surfaces with different wettabilities was numerically investigated by using the method of coupled level set and volume of fluid, and a high-speed video experiment was used to validate the simulation results. The simulated coalescence behavior of droplets is consistent with the experiment results. We compared droplets with different Weber numbers (3.67 <= We <= 50) coalescing on solid surfaces of different wettabilities and contact angles (80 degrees <= alpha <= 160 degrees). The result is a regional division diagram that relates Weber number and contact angle based on different coalescence phenomena. The factors causing droplet deposition, air entrapment, bounce, and partial bounce during collision coalescence are described based on an analysis of interactions involving inertial forces, surface tension, and wall adhesion forces. Furthermore, the effect of Weber number and contact angle on droplet coalescence behavior is elaborated by analyzing the relationship between coalescence time and wettability radius under different Weber numbers and contact angles. Finally, through an energy analysis, we explain the maximum spreading radius and oscillation of droplets with different Weber numbers on solid surfaces with different wettabilities and in the process of head-on-collision coalescence. Published under an exclusive license by AIP Publishing.

Automated summary

The head-on-collision coalescence dynamics of droplets on surfaces with different wettabilities were studied using numerical simulation and experimental validation. The study found that droplets exhibit different coalescence phenomena based on Weber number and contact angle, and the behavior can be explained by analyzing the interactions involving inertial forces, surface tension, and wall adhesion forces.