Molecular dynamics study of nanoscale droplets impacting on textured substrates of variable wettability

Abstract

The impact of nanodroplets on a solid surface is widely encountered in industrial processes. Understanding the processes that occur when nanodroplets impact a rough surface is of great significance, but the mechanism and dynamics of these processes remain unclear due to the limitations of experimental tools and the shortcomings of most macroscale models. This paper describes molecular dynamics simulations conducted to explore these nanoscale processes. The wettability and solid fraction of the textured substrate and the effects of different impact velocities are investigated. We demonstrate that the maximum spreading time can be described as a power law of the Weber number and that the maximum spreading factor increases with increasing surface wettability. Owing to changes in the attraction between the nanodroplets and the textured substrate, the maximum spreading factor also increases as the solid fraction increases. Based on energy analysis, a theoretical model is proposed for predicting the maximum spreading factor, and this is found to be in good agreement with the simulation results. The results of this study provide useful guidance for predicting the dynamics of nanodroplet impacts.