Droplet impact and rebound dynamics on superhydrophobic surfaces
Fang-Fang Zhang, Shuyan Che, Jingdan Tang, Chuang-Yao Zhao
Abstract
The impact and rebound dynamics of droplets on superhydrophobic surfaces were investigated through numerical analysis employing the phase field method. The influences of contact angle, impact velocity, surface tension, and dynamic viscosity on the fields of pressure and velocity as well as the spreading factor and central height were described comprehensively. The results indicate that there are a series of stages of impingement, spreading, transition, retraction, and rebound in order throughout the life cycle of a droplet. The droplet exhibits distinct pressure and velocity profiles upon impingement stage, with the maximum pressure at the lower center and higher velocities at the upper periphery, spreading around. Velocities are predominantly upward, peaking at the bottom of the droplet during the rebound stage. A larger contact angle, viscosity, surface tension, and lower impact velocity contribute to a reduced maximum spreading factor. Deposition is more likely to occur when the impact velocity, surface tension is lower, and the viscosity is larger. Droplets tend to rebound when the contact angle, impact velocity, and surface tension are larger. Thresholds for impact velocity, surface tension, and viscosity were delineated for droplet rebound. Furthermore, a correlation for predicting the maximum spreading factor of droplets on superhydrophobic surfaces was proposed.