title: Generalized second-order slip boundary condition for nonequilibrium gas flows.
abstract: It is a challenging task to model nonequilibrium gas flows within a continuum-fluid framework. Recently some extended hydrodynamic models in the Navier-Stokes formulation have been developed for such flows. A key problem in the application of such models is that suitable boundary conditions must be specified. In the present work, a generalized second-order slip boundary condition is developed in which an effective mean-free path considering the wall effect is used. By combining this slip scheme with certain extended Navier-Stokes constitutive relation models, we obtained a method for nonequilibrium gas flows with solid boundaries. The method is applied to several rarefied gas flows involving planar or curved walls, including the Kramers' problem, the planar Poiseuille flow, the cylindrical Couette flow, and the low speed flow over a sphere. The results show that the proposed method is able to give satisfied predictions, indicating the good potential of the method for nonequilibrium flows.
authors.affiliation: State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan 430074, China and Beijing Computational Science Research Center, Beijing 100084, China.
authors.forename: Zhaoli
authors.initials: Z
authors.lastname: Guo
authors.affiliation: State Key Laboratory of Enhanced Oil Recovery, Research Institute of Petroleum Exploration and Development, Beijing 100083, P. R. China.
authors.forename: Jishun
authors.initials: J
authors.lastname: Qin
authors.affiliation: State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan 430074, China.
authors.forename: Chuguang
authors.initials: C
authors.lastname: Zheng