Modeling and Simulation of Correlation between Velocity Slip at Wall Boundary and Effective Viscosity of Rarefied Gas

The velocity slip of the lubricating gas-film was mathematically modeled in stratification theory, theoretically analyzed in gas kinetics, numerically simulated with software LAMMPS/2DMD, and experimentally evaluated. The influence of the temperature, viscosity and thickness of gas-film on the velocity slip in the near-wall/continuous-flow/rarefied gas layers was investigated. The calculated and simulated results show that depending on the temperature and viscosity, the rarefied gas layer strongly affects the velocity slip. For example, in the rarefied layer, the velocity increases with the increasing distance from the wall; in the near-wall layer, the velocity decreases sharply for interfacial friction; in the continuous flow layer, gas molecule flows in full slip mode. Besides, the velocity and the velocity difference between the rarefied and near-wall layers increase with an increase of temperature and/or a decrease of viscosity; at a fixed temperature, the dimensionless slip length ls linearly depends on Kn number.