Improved treatment of the open boundary in the method of Lattice Boltzmann equation

The method of Lattice Boltzmann equation (LBE) is a kinetic-based approach for fluid flow computations. In LBE, the distribution functions on various boundaries are often derived approximately. In this paper, the pressure interaction between an inlet boundary and the interior of the flow field is analysed when the bounce-back condition is specified at the inlet. It is shown that this treatment reflects most of the pressure waves back into the flow field and results in a poor convergence towards the steady state or a noisy flow field. An improved open boundary condition is developed to reduce the inlet interaction. Test results show that the new treatment greatly reduces the interaction and improves the computational stability and the quality of the flow field.