Dynamical analysis of droplet impact spreading on solid substrate

Abstract

This paper investigates the impact spreading of a droplet on a solid substrate using numerical simulation on the basis of a volume-of-fluid (VOF) model. The process of droplet spreading is described, the analysis of low speed and high speed droplet spreading, and more than one droplet spreading simultaneously is performed. The pressure, velocity, and spreading factor during the droplet spreading are reported. According to the spreading factor’s evolvement, the process of droplet spreading can be classified into spreading phase and recoiling phase. The spreading factors are almost the same at the low speed droplet spreading; however, the pressures on the substrate are quite different and air entrainment may be found as the impact speeds in a certain range. The impact speed impacts on the spreading factors in high speed droplet spreading. The spreading factor obviously increases with increasing impact speed; however, splashing will appear in the status when the speed is high enough in the high speed droplet spreading. The distance between the neighbor droplets affects the film’s quality, and only the distance between the static diameter and the maximum diameter can ensure the film’s quality. The results could help in understanding the process of droplet spreading and provide advice on the operation of a spray coating process.

Keywords

droplet / impact spreading / numerical simulation