Dynamic behaviors of two droplets impacting an inclined superhydrophobic substrate

We investigate the dynamic behaviors of two droplets simultaneously impacting an inclined superhydrophobic substrate via lattice Boltzmann method simulations. We discover that, for the case of two droplets impacting an inclined substrate, there are three rebound patterns depending on the droplet spacing and the inclination angle, i. e., a complete-coalescence-rebound (CCR) pattern, a partial-coalescence-rebound (PCR) pattern, and a nocoalescence-rebound (NCR) pattern. Intriguingly, the inclination angle shows completely opposite effects on the rebound dynamics, i.e., when the droplets are placed laterally, the PCR pattern is more restricted and the contact time is more delayed with increasing of the inclination angle; while when the droplets are placed tangentially, the PCR pattern is more promoted and the contact time is more shortened. More interestingly, once the rebound pattern changes, the contact time changes dramatically, especially when the rebound pattern transforms from CCR/NCR to PCR, the contact time presents a sudden and significant decrease. These findings provide new insights into estimation of the contact time of multiple droplets impacting an inclined superhydrophobic substrate.