(a) Simulation data is fitted with theories from Refs. [23], [24], [32], [34], and [36] In the simulations, the wall friction is set as 0.5. The enlarged graph shows the details of the fitting about normalized force from 0 to 2. (b) Simulation data is fitted with theories from Refs. [24], [34], and [36] along using Eq. (4). In the simulations, the wall friction is set as 0.0. The enlarged graph shows the details of the fitting about normalized force from 0 to 2.