Simulating two- and three-dimensional microflows by the lattice Boltzmann method with kinetic boundary conditions

An entropic lattice Boltzmann model for gaseous slip flow in microchannels is presented. We relate the Knudsen number with the relaxation time in the lattice Boltzmann evolution equation from the gas kinetic theory. The slip velocity taking the momentum accommodation coefficient into account at the solid boundaries is obtained with kinetic boundary conditions. The two-dimensional micro-Poiseuille flow, microflow over a backward-facing step, micro-lid-driven cavity flow, and three-dimensional microflow are simulated using the present model. Numerical tests show that the results of the present lattice Boltzmann method together with the boundary scheme are in good agreement with the analytical solutions and numerical simulations by the finite volume method.