Fig. 1.

Universal scaling of the contact number. Symbols denote the numerical result, while the solid line denotes the theoretical prediction $\delta z\sim {\mathrm{\Delta }}^{1/2}$. Data for nonspherical particles are reproduced from ref. 40, and from the sphericity $A$, we defined $\mathrm{\Delta }=c{\left(A-1\right)}^{1/2}$, which recovers the correct scaling relation between the sphericity and aspect ratio of ellipses for small $\mathrm{\Delta }$. We set $c=1/6$ to collapse all data. Data for the BP correspond to a pressure $p=10^{-6}$.