Droplet Collision and Nucleation Hydrodynamics on Superhydrophobic Cylindrical Surfaces

Abstract

Water drop impact onto hydrophobic cylindrical surfaces with four different curvature ratio were experimentally investigated. At lower Weber number impact droplet asymmetrically bounces from all curvature cases with increase in Weber number droplet starts splitting/splashing. On higher striking velocity, the stretched lamella shatters into several small droplets. The high velocity impact droplets ruptures rapidly by formation of nucleation holes on the film as a result of small scale roughness on contact surface. The small scale roughness on test surface causes hole nucleation/film rupturing and reduces the contact time. As the impinging velocity reaches the maximum of our experimental study, the contact time was observed to be even less that the capillary time (tc < τ0). Due to complete shattering of water drop, the retraction time is absent in these cases and results in reduced contact time. It was found that the number of nucleations is in proportion with velocity of impact and contact area on striking.