In the LBM, the so-called bounce back boundary condition is widely used at walls to obtain the no-slip velocity conditions.Implementation of this kind of boundary condition is quite easy and straightforward. The bounce back scheme implies that when a particle streams to a wall node, it scatters back to the node it came from. Since the LBM involves second-order spatial discretization, the effective position of the wall is considered to be located between the actual wall and the first row of the fluid domain mesh.This would cause the bounce-back scheme to become second order accurate. The schematic representation of the bounce-back boundary condition is shown in Fig. 2.