Figure 13. Contact numbers for three contact types (L-L, L-S and S-S) for different mixtures.
The contact numbers for the three contact types for the different mixtures are normalized and shown in Figure 14. The L-L and L-S contact numbers are normalized by the number of large particles in the given mixture, and the S-S contact number is normalized by the number of small particles. From the perspective of normalized contact number, the L-S contact is the dominant type of contact for the binary mixtures, indicating that for the current particle size ratio of 4.5, the large particles in the binary mixtures are surrounded by small particles sticking to the surface. The normalized L-S contact number for the binary mixtures ranges from 45 to 12 and decreases with increasing mass fraction of large particles. The significant difference in normalized L-S contact number for various composition indicates that different composition has different contact structure. This is especially true for the contact structure around the large particles, which may also affect the motion of particles and contribute to the shear stress difference.