Water droplet impact on superhydrophobic surfaces with various inclinations and supercooling degrees

Water droplet freezing on the surface structures has a gigantic impact on the aircraft, power transmission lines and industrial facilities. Thereby, it is essential and meaningful to clearly understand the droplet impacting and icing behaviors on the supercooled superhydrophobic surface at an angle for the prevention of ice accretion. In the present research, the dynamic behaviors of a water droplet impacting on the superhydrophobic surface with different inclination and supercooling degree were visually studied by a high-speed camera. Moreover, the droplet dynamic behaviors were analyzed in terms of the contact time, freezing onset time, maximum spreading factor, rebounding energy, average sliding velocity and adhesion morphology on the surface. The results prove that the droplet rebounding process can be promoted by increasing the surface inclination. Moreover, with the gradually decreasing surface temperature the droplet successively undergoes full rebound, partial rebound and no rebound on the surface with an inclination of 30°, and the boundary temperatures of these three modes are −31.25 and −33.75 °C, respectively. Furthermore, the governing factor of the superhydrophobic surface anti-icing performance turns from the droplet rebounding energy into the average sliding velocity with an increase in the surface inclination, and the surface with an inclination of 30° has the best anti-icing performance. It is worth noting that reducing the surface de-icing difficulty rather than improving the anti-icing performance is more suitable for the extremely cold environment.