Molecular Dynamics Simulations on Flow Properties of Gas Mixture in Nanochannels

The simulations for gas flow in nanochannels has attracted considerable attention in design and manufacturing of gas nanofluidic control devices. Molecular dynamics simulations were used to study the flow properties of gas mixture including nitrogen (N₂), oxygen (O₂) mixture and carbon dioxide (CO₂) confined in parallel-plate. Results show that the boundary slip velocity of the gas mixture increases with increasing the percentage of CO₂. When the component ratio of CO₂ is less than 20%, the velocity profile of the gas mixture along the channel width direction exhibits linearity. As the component ratio of CO₂ increases up to 40%, the nonlinear velocity profile appears. For the component ratio of 20%-CO₂, the boundary slip decreases with the increase of the width of the nanochannel. The influences of gas density and gas-solid coupling intensity on the boundary slip of gas mixture are explored, and the boundary slip increases with decreasing the density of the mixture. As the gas-solid coupling strength is enhanced, more gas molecules are adsorbed on the solid surface, further resulting in the stick-slip state at the solid-gas interfaces. Therefore, the shear strain rate increases and the boundary slip decreases with increasing the coupling strength caused by the accumulation of gas molecules at the boundaries.