Multiphase water flow inside carbon nanotubes

Abstract

We present nonequilibrium molecular dynamics simulations of the flow of liquid–vapour water mixtures and mixtures of water and nitrogen inside carbon nanotubes. A new adaptive forcing scheme is proposed to impose a mean flow through the system. The flow of liquid water is characterised by a distinct layering of the water molecules in the vicinity of the boundary and a slip length that is found to increase with the radius of the carbon nanotube. Increasing the temperature and pressure of the system furthermore results in a decrease in the slip length. For the flow of mixtures of nitrogen and water we find that the slip length is reduced as compared to the slip for the pure water. The shorter slip length is attributed to the fact that nitrogen forms droplets at the carbon surface, thus partially shielding the bulk flow from the hydrophobic carbon surface.