Rebound dynamics of two droplets simultaneously impacting a flat superhydrophobic surface

In this letter, we investigate the rebound dynamics of two equally sized droplets simultaneously impacting a superhydrophobic surface via lattice Boltzmann method (LBM) simulations. We discover three rebound regimes depending on the center-to-center distance between the two droplets: a complete-coalescence-rebound (CCR) regime, a partial-coalescence-rebound (PCR) regime, and a no-coalescence-rebound (NCR) regime. We demonstrate that all the rebound regimes are closely associated with dynamic behaviors of the formed liquid ridge or bridge between the two droplets. We also present the contact time in the three regimes. Intriguingly, although partial coalescence takes place, the contact time is still dramatically shortened in the PCR regime, which is even smaller than that of single-droplet impact. These findings provide new insights into the contact time of multiple-droplet impact and thereby offering useful guidance for some applications such as anti-icing, self-cleaning, and so forth.