Experimental investigation on the impacting and freezing characteristics of water droplets on a PDMS-decorated superhydrophobic aluminum alloy surface

Due to the potential applications of superhydrophobic surfaces in water-repelling and anti-icing, it is of great interest to study the impacting and freezing processes of water droplets on superhydrophobic surfaces. In this study, the process of a water droplet impacting the PDMS-decorated superhydrophobic aluminum alloy (denoted as Al-PDMS) surface was studied, and the influences of a water droplet falling height and volume were systemically investigated with a high-speed camera. The results indicate that the impacting process can be categorized into four states, which are mainly affected by the dropping height. The bouncing processes of water droplets on horizontal superhydrophobic surfaces are studied by defining spreading factor alpha and rebounding factor beta. Furthermore, the effect of the inclination angle phi of the superhydrophobic plate on the impacting behavior was investigated. The freezing processes of water droplets on superhydrophobic surfaces were also studied. The results showed that the delayed-icing time decreases with decreasing test plate temperature. Additionally, the volume and height of the frozen portion of the water droplets during freezing were investigated, and the movement characteristic of the freezing front was analyzed.