Universality of stress-anisotropic and stress-isotropic jamming of frictionless spheres in three dimensions: Uniaxial versus isotropic compression

We numerically study a three-dimensional system of athermal, overdamped, frictionless spheres, using a simplified model for a non-Brownian suspension. We compute the bulk viscosity under both uniaxial and isotropic compression as a means to address the question of whether stress-anisotropic and stress-isotropic jamming are in the same critical universality class. Carrying out a critical scaling analysis of the system pressure p, shear stress sigma, and macroscopic friction mu = sigma/p, as functions of particle packing fraction phi and compression rate , we find good agreement for all critical parameters comparing the isotropic and anisotropic cases. In particular, we determine that the bulk viscosity diverges as p/ similar to (phi J - phi)-beta, with beta = 3.36 +/- 0.09, as jamming is approached from below. We further demonstrate that the average contact number per particle Z can also be written in a scaling form as a function of phi and . Once again, we find good agreement between the uniaxial and isotropic cases. We compare our results to prior simulations and theoretical predictions.

Automated summary

This study numerically investigates a three-dimensional system of athermal, overdamped, frictionless spheres using a simplified model. The bulk viscosity is computed under compression to explore the question of whether stress-anisotropic and stress-isotropic jamming belong to the same critical universality class. The results demonstrate that the bulk viscosity diverges as jamming is approached and are consistent for different scenarios.