Supercritical CO-induced atomistic lubrication for water flow in a rough hydrophilic nanochannel.

A fluid flow in a nanochannel highly depends on the wettability of the channel surface to the fluid. The permeability of the nanochannel is usually very low, largely due to the adhesion of fluid at the solid interfaces. Using molecular dynamics (MD) simulations, we demonstrate that the flow of water in a nanochannel with rough hydrophilic surfaces can be significantly enhanced by the presence of a thin layer of supercritical carbon dioxide (scCO2) at the water-solid interfaces.

Molecular simulation of carbon dioxide, brine, and clay mineral interactions and determination of contact angles.

Capture and subsequent geologic storage of CO2 in deep brine reservoirs plays a significant role in plans to reduce atmospheric carbon emission and resulting global climate change. The interaction of CO2 and brine species with mineral surfaces controls the ultimate fate of injected CO2 at the nanoscale via geochemistry, at the pore-scale via capillary trapping, and at the field-scale via relative permeability. We used large-scale molecular dynamics simulations to study the behavior of supercritical CO2 and aqueous fluids on both the hydrophilic and hydrophobic basal surfaces of kaolinite, a common clay mineral.

Limitations and recommendations for the calculation of shear viscosity using reverse nonequilibrium molecular dynamics.

The reverse nonequilibrium molecular dynamics (RNEMD) method calculates the shear viscosity of a fluid by imposing a nonphysical exchange of momentum and measuring the resulting shear velocity gradient. In this study we investigate the range of momentum flux values over which RNEMD yields usable (linear) velocity gradients. We find that nonlinear velocity profiles result primarily from gradients in fluid temperature and density.