Abstract: In order to investigate the aerodynamic performance of circular cylinders in a pin pulverizer, the computational fluid dynamics method was applied in the study of flow past a circular cylinder nail in a 2D model. The problem of flow around a circular cylinder in uniform inflow was used to verify the correctness of the computational model. The independence of mesh and time step were also investigated. The results showed that flows could be classified into three flow regimes when Reynolds numbers varied within 200. In the stable separating regime, the max length of closed wakes was approximately equaled to the diameter of the cylinder, and the wakes would vanish as the increasing of Reynolds number. In the unstable vortex shedding regime, periodical vortices shedding occurred at low Reynolds numbers. Lift force and drag force on the cylinder were small. As Reynolds number grew, the dimensionless frequency increased and different frequency components appeared. The dimensionless frequency was one order of magnitude smaller than that of the flow around a cylinder in uniform inflow. It lays the foundation of the research on the problem of flow around cylinders at high Reynolds numbers.