Coordination number and geometric anisotropy in binary sphere mixtures

In this paper the structure of binary mixtures of spherical particles obtained by numerical simulations is analyzed. The study addresses porosity, global and partial (by size particle) coordination number and anisotropy in contacts distribution. The effect of interparticle friction coefficient, small particle proportion and diameter ratio on the coordination number (Nc) is evaluated. The results show that partials coordination numbers depend mainly on geometrical aspects. The average coordination number ((Nc) under bar) of large spheres (ls) with small spheres (ss) increases rapidly with diameter ratio and small particles proportion, but partial (Nc) under bar of ss with ss, ss with ls and ls with ls present only slight changes and the global (Nc) under bar remains constant. These results are compared with those of experimental works. The global anisotropy in a binary mixture may be very different of anisotropy by particle size, since the small particles accumulate over large ones. It is shown that the friction coefficient plays an important role in contacts distribution.