Molecular dynamics study on effects of nanostructured surfaces on heterogeneous nucleation of liquid droplets

Abstract

Heterogeneous nucleation of droplets on a solid surface with and without nanostructures was investigated by the classical molecular dynamics simulations. The simulations investigated effects of the nanostructures on the condensation processes and the nucleation rates. The calculation system was consisted of the fluid molecules(Ar) and the solid atoms(Pt) which interact through the 12-6 Lennard Jones(LJ) potential function, and a liquid membrane existed in the vicinity of the upper solid surface at the initial condition. Then, we changed the temperature of the lower solid wall to a lower value, which enabled us to investigate the nucleation processes in the vicinity of the lower solid surface with and without the nanostructures under a constant pressure. The potential functions between the fluid molecules and solid atoms were also assumed to be the LJ form, and the energy scale parameter between fluid molecules and solid atoms was changed to simulate a hydrophobic surface. The results showed that clusters tend to be formed near the side walls of the nanostructures and grow between the nanostructures. It was also shown that the nucleation rate is influenced by morphology of the nanostructures; the nucleation rate increases with the increase of the height of the nanostructures and with the decrease of the spacing between the nanostructures. Furthermore, the results revealed that there is a positive correlation between the nucleation rate and the heat flux measured at the lower solid wall.

Keywords

• non-equilibrium molecular dynamics simulation
• heterogeneous nucleation
• nucleation rate
• condensation
• heat flux
• nanostructures