Contact Time of Double-Droplet Impacting Superhydrophobic Surfaces with Different Macrotextures

The contact time of droplets on superhydrophobic surfaces is an especially important parameter in many applications, such as self-cleaning, anti-icing, and spray cooling. In this study, we investigate the contact time of two identical droplets simultaneously impacting superhydrophobic surfaces decorated with three different macrotextures, i.e., bathtub-like groove (S1), vertical wall (S2), and rectangular ridge (S3), via lattice Boltzmann method (LBM) simulations. We explore influences of the geometrical parameters of the macrotextures, as well as the center-to-center distance of the two droplets, on the contact time. We found a new rebounding regime with significantly reduced contact times. We demonstrate that, as compared with impacting a smooth superhydrophobic surface, the contact time can be decreased by 41% for macrotexture S1 because of the asymmetric spreading and retraction of droplets motivated by the macrotexture. We also demonstrate that the new regime depends on the center-to-center distance and geometrical parameters of the macrotextures.