Numerical investigations of the spreading and retraction dynamics of viscous droplets impact on solid surfaces

Abstract

This study uses an efficient, continuum-level modeling method to investigate the spreading and retraction dynamics of viscous droplets impact on flat solid surfaces. The main advantage of this method is that it employs the notion of disjoining pressure to avoid the specification of contact angle boundary in traditional modeling methods. Thus, the dynamic contact angle and contact line motion are derived more physically as a result of the combined action of capillary and disjoining pressure. Based on this modeling method, we systematically analyze the influence of droplet viscosity, impact velocity and material wettability on the dynamic characteristics of droplets. Multiple general correlations are developed to predict the spreading factor β during the kinematic phase, the maximum spreading factor βmax, the minimum film thickness hc,min and the retraction rate ε˙, which are all in good agreement with previous theoretical models. In addition, this paper also discusses the applicability and limitations of these models. Finally, we have successfully proved that this modeling method can be reliably applied to the investigations of both droplet spreading and retraction process.