Anti-freezing characteristics of water droplet impinging the superhydrophobic surface: An experimental and predictive study

Water freezing has a significant and non-negligible influence on the aircraft, power transmission lines and operational efficiency of industrial facilities. Therefore, it is of great value and meaning to deeply understand the dynamic behaviors of water droplet impacting the supercooled superhydrophobic surface. In this work, effects of impact velocity, surface temperature and inclined angle on the impinging droplet dynamics are visually investigated. The machine learning model is first proposed to predict the rebound height and temperature limit of fully rebound. The results demonstrate that a larger impact velocity shifts the temperature limit of completely rebound to a higher surface temperature. However, it has little effect on the spreading time and contact time. As the temperature further decreases, portion of droplet is pinned on the substrate instead of fully rebound and the volume of residual droplet increases. As the inclined angle increases, both contact time and rebound height decreases. Due to driven by the tangential component of gravity, width of droplet before detachment increases while the stretched length decreases. The optimal temperature limit of fully rebound is -35 degrees C with the inclined angle of 30 degrees and We = 19, showing a significant improvement compared to the temperature limit on a horizontal surface.