Couette flow of pentane in clay nanopores: Molecular dynamics simulation

Shear flow of n-pentane in slit nanopores between clay surfaces is investigated by molecular dynamics simulations. Pyrophyllite and hydrated Na-montmorillonite are considered as representative examples of hydrophobic and hydrophilic clay surfaces, respectively. The viscosity-density relations and slip lengths are calculated for both pentane-clay interfaces for different pore widths. The results show that the viscosity-density dependencies for n-pentane are not changed by the confinement in pores with sizes from 3 to 7 nm, compared to the bulk liquid. At the pyrophyllite-pentane interface the slip length is 0.29 nm on average for all studied densities and pore sizes. However, the slip length is negligible at the montmorillonite-pentane interface, likely due to the microscopic roughness of the interface between pentane and the adsorbed water layer. The orientation analysis shows some preference for pentane mole-cules ordering parallel to the wall surfaces, which is stronger in pyrophyllite pores compared to the montmorillonite, suggesting an influence of the details of fluid-wall interaction on the liquid structure in nanopores.(c) 2022 Published by Elsevier B.V.