Simulation studies on fluid density distribution of micro-flows in a nano-channel

The flow in microchannel involves many microscale effects, because of its large ratio of superficial area to volume. And it further causes the density profiles of flow in microchannel to be greatly different from in the macro-channel. In this paper we investigate the effects of three factors (ε_LL, σ_LL, σ_LS) on density profile of micro-flow via the Poiseuille flow in a nanochannel using none-equilibrium molecular dynamics simulation method. In our study, we selected NVE as the statical ensemble, LJ/126 model as the potential energy function. We also adopt the Rigid-atom model to describe the wall and the temperature thermostat through using the time/rescale methods. The motion equations are solved using Verlet algorithm. The results show that as the interaction between flow atoms decreases, the oscillation degree of density profiles near the wall increases. The balance distance (σ_LL) between flow atoms affects the existence state and density profiles of flow in the micro channel: the greater σ_LL causes the flow atoms to be arranged as the fcc structure liking a solid, while smaller σ_LL results in the flow atoms moving as a changeable "cluster". The balance distance (σ_LS) between wall atoms and flow atoms also has a significant influence on flow density. As σ_LS increases, the oscillation degrees of density profile near the wall and the distance between the starting point of density profile and wall increase. Besides, we analyze the mechanism of effects of the interaction between the flow atoms on density distribution based on the "capture-escape" behavior of atoms adjoining the wall.