Non-equilibrium extrapolation method for velocity and pressure boundary conditions in the lattice Boltzmann method

Abstract

In this paper,we propose a new approach to implementing boundary conditions in the lattice Boltzmann method (LBM).The basic idea is to decompose the distribution function at the boundary node into its equilibrium and non-equilibrium parts,and then to approximate the non-equilibrium part with a first-order extrapolation of the nonequilibrium part of the distribution at the neighbouring fluid node.Schemes for velocity and pressure boundary conditions are constructed based on this method.The resulting schemes are of second-order accuracy.Numerical tests show that the numerical solutions of the LBM together with the present boundary schemes are in excellent agreement with the analytical solutions.Second-order convergence is also verified from the results.It is also found that the numerical stability of the present schemes is much better than that of the original extrapolation schemes proposed by Chen et al.(1996 Phys.Fluids 8 2527).