Physical symmetry, spatial accuracy, and relaxation time of the lattice Boltzmann equation for microgas flows

In this paper, we study systematically the physical symmetry, spatial accuracy, and relaxation time of the lattice Boltzmann equation (LBE) for microgas flows in both the slip and transition regimes. We show that the physical symmetry and the spatial accuracy of the existing LBE models are inadequate for simulating microgas flows in the transition regime. Our analysis further indicates that for a microgas flow, the channel wall confinement exerts a nonlinear effect on the relaxation time, which should be considered in the LBE for modeling microgas flows.