Droplet impact on to a rough surface

Abstract

The effect of surface roughness on droplet impact is considered. If a surface is sufficiently rough, then models of droplet impact need to be altered to include the possibility of many touchdowns between the fluid and the solid. The subsequent simultaneous motion of several contact points is therefore described. In particular, results are presented for the contact point motion during the impact of a sheet of water on to a periodic rough surface. A model for multiple contact point motion is also analysed for cases of deep surface roughnesses. The analysis is complemented by a direct numerical simulation using the volume of fluid method. The effect of surface roughness is to reduce the rate at which the droplet spreads. Comparisons between various roughness shapes are considered numerically and analytically. Possible applications are then discussed, especially in the context of aircraft icing. © The author 2011. Published by Oxford University Press. all rights reserved.