Lattice Boltzmann simulation of droplet impact dynamics on superhydrophobic surface decorated with triangular ridges

Abstract

The rapid rebound of droplets impacting on superhydrophobic surfaces is used in a wide range of applications such as anti-icing, anti-forcing and self-cleaning. In this study, the droplet impacting a superhydrophobic surface equipped with macroscopic triangular ridges is simulated using the three-dimensional lattice Boltzmann method (LBM) and focus on the effects of Weber number (We) and the number of ridges on the dynamic behavior and contact time. For the single ridge, as We increase, the droplet gradually form a ring shape and the splits. The appearance of ring shape leads to a rapid decrease in contact time t * , which is because an opposite fluid movement in the inner and outer edges collides with each other and generate an upward velocity that facilitate the droplet bouncing. Base on the single ridge, the structure of cross ridges and quadruple ridges are proposed to research the effect of different number of ridges to the contact time. It can be found that the contact time and phenomenon between cross and quadruple ridges are similar, and the contact time decreases by about 50–66.7 % substantially and has a limited time compared to the single ridge, although there is no break or ring forming before they rebound. Therefore, the crossed ridges(collective name for cross and quadruple ridges) structure helps to reduce the contact time of droplets impacting the superhydrophobic surface, but an excessive number of ridges should be avoided.