Abstract: Removing mass leakage in non-equilibrium extrapolation method,a mass conservative boundary condition is proposed with improving non-equilibrium extrapolation method based on conservation of mass.Mass conservation of a system is ensured by defining an artificial density at solid boundary.Precision and stability of the new boundary condition are validated by simulating three classical flows (Poiseuille,Couette and Womersley).

Key words: non-equilibrium extrapolation method, lattice Boltzmann method, conservative boundary condition