Analysis of reflective and non-reflective boundary conditions in LBM simulations of flow past an obstacle in a channel

This paper analyses the effects of considering non-reflective (characteristic boundary conditions) versus reflective boundary conditions (BCs) on the flow past a square object. We observe a clear dependence of the force exerted over the obstacle on the choice of BCs. Recirculation lengths, lift and drag coefficients, phase diagrams and streamlines for several angles of incidence are compared for a range of low Reynolds numbers (50–150) and two different values of the ratio of the object cross section to the channel width, 1/8 and 1/16. We remark distinct effects depending on the combination of BCs used at the inlet and at the outlet.