Molecular Dynamics Simulation of Slip-Transitional Flows in Nano-Channels

The detailed near wall flow behavior in nanochannels depending on the surface structure is investigated by performing equilibrium molecular dynamics simulations. The nanoCouette flows and force driven nano-Poiseuille flows are considered. The simulated flow conditions are in the slip-transitional flow regime since the estimated Knudsen number is Kn=0.2. Due to the effects of the surface structure, it is confirmed that the velocity profile very near a wall varies depending on the surface structure. It is also found that the Knudsen layer profile in nanoflows deviates from that by the gas kinetic theory in the vicinity of the wall surface. By the interaction between a fluid molecule and the wall molecules, the fluid molecule staying in the wall vicinity is less strongly stuck to the wall than those at a little away from the wall surface. This effect produces a hook like velocity distribution near the wall which is hardly described by the Boltzmann equation for rarefied gas flows.