Water droplet impact phenomena on super-hydrophobic surface

Abstract

The water droplet impact phenomena on the super-hydrophobic surface of plasma-treated polypropylene film coated on a glass surface were investigated by using a high-speed solid-state CCD camera. The experiments were conducted at an impact height of 10 mm, with three different sizes of water droplets: 5.9650, 10.9691, and 12.6049 mm3 and impact height of 20 mm with a size of water droplet 11.0941 mm3. The volumes and the center of mass of falling and rebounding droplets obtained from using the 2007 version of AutoCAD software were used to calculate the change in energy stage. The results showed that water droplets of both 5.9650 and 10.9691 mm3 exhibited 4 total rebounds without droplet splash, whereas the largest droplet, 12.6049 mm3, showed only 2 rebounds. The bigger the droplet size, the greater the energy loss. In addition, the greater the initial impact velocity, the greater the energy loss. The movement of center of mass showed that during the water droplet rebound, there were two peaks, unlike a solid particle free falling body having a single maximum peak. The two peak maxima are due to the water moving inside the liquid body during rebounding.