The combination bounce back model for Lattice Boltzmann Method and its application on gas flow in micro machinery

Extensive study of micro flow in rectangular channel is considered and analyzed. Numerical studies are performed by Lattice Boltzmann Method. A new combination bounce back model for the treatment of solid boundary condition is proposed. Then, three solid boundary conditions are implemented in micro rectangular channel flow. These include non-slip bounce back rule, traditional combination bounce back rule and the proposed combination bounce back rule. It is observed that the width-to-height ratio (W/H) is the major influencing parameter for rectangular micro-channel flow in low Reynolds number. And, it is also found that the drag coefficient of traditional combination bounce back rule is maximum followed by those of the proposed combination bounce back rule and non-slip bounce back rule. In non-slip bounce back rule, particles bounce back alone the opposite direction when they collide with solid boundary node and it indicates maximum drag in the macro flow. In the traditional combination bounce back rule, some particles reflect based on mirror face with non-zero tangential solid velocity. It indicates that the tangential velocity of particles is same with its original velocity. And, this leads to the minimum drag. The proposed combination bounce back velocity is somewhere in between those of bounce back rule and first combination bounce back rule.