Experimental Investigation of Water Droplet Impact on the Electrospun Superhydrophobic Cylindrical Glass: Contact Time, Maximum Spreading Factor, and Splash Threshold

The impinging of water droplets on superhydrophobic cylindrical glasses has been investigated experimentally by using a high-speed camera. The superhydrophobic cylindrical surfaces were fabricated by electrospinning technique combined with silane treatment. The effects of the diameter ratio of cylindrical glass and Weber number on the postimpact regime, contact time, maximum spreading factor, and splash threshold were investigated in the ranges 3.5–16 and 27–161, respectively. The results were compared with impact droplets on superhydrophobic flat glass and uncovered hydrophilic cylindrical glass. Three types of regimes were observed on hydrophilic and superhydrophobic cylindrical glasses including coating, splash, and splash-rebound. Results showed that contact time on the cylindrical surface is up to 50% less than the flat one. Moreover, the splash regime was started at the critical Weber number = 134 on high-diameter-ratio superhydrophobic cylindrical and flat surfaces while happening earlier when the diameter ratio is below D * < 4.