Abstract: Two approaches, the momentum-exchange method and the stress-integration method, for force evaluation based on the Lattice Boltzm ann equation were investigated. The momentum-exchange method is relatively reliable, accurate, and easy to implement for both two-dimensional and three-dimensional flows. The flow around a cylinder was simulated, and the drag coefficient of the cylinder was evaluated by the momentum-exchange method. The drag coefficient of a concave surface was also evaluated and compared with the theoretical drag coefficient of a plane. The numerical results are valid, and the drag coefficient of the concave surface is close to that of the plan with the increase of Re number.

Key words: Lattice Boltzmann method, momentum-exchange method, stress-integration method, drag coefficient