Critical Scaling of Bagnold Rheology at the Jamming Transition of Frictionless Two Dimensional Disks

TL;DR

This study performs detailed simulations of shear-driven rheology in 2D frictionless disks to analyze the critical scaling near jamming, finding a critical exponent larger than some theoretical predictions and confirming the applicability of scaling theory.

Contribution

It provides a comprehensive critical scaling analysis of Bagnold rheology at the jamming transition, including correction-to-scaling terms and comparison with theoretical models.

Findings

Critical exponent β ≈ 5.0 ± 0.4, larger than some predictions.

Results consistent with previous numerical and theoretical studies.

Confirmation that shear-driven jamming follows a critical scaling framework.

Abstract

We carry out constant volume simulations of steady-state, shear driven, rheology in a simple model of bidisperse, soft-core, frictionless disks in two dimensions, using a dissipation law that gives rise to Bagnoldian rheology. We carry out a detailed critical scaling analysis of our resulting data for pressure $p$ and shear stress $\sigma$, in order to determine the critical exponent $\beta$ that describes the algebraic divergence of the Bagnold transport coefficients, as the jamming transition is approached from below. We show that it is necessary, for the strain rates considered in this work, to consider the leading correction-to-scaling term in order to achieve a self-consistent analysis of our data. Our resulting value $\beta\approx 5.0\pm 0.4$ is clearly larger than the theoretical prediction by Otsuki and Hayakawa, and is consistent with earlier numerical results by Peyneau and Roux, and recent theoretical predictions by DeGiuli et al. We have also considered the macroscopic friction $\mu\equiv \sigma/p$ and similarly find results consistent with Peyneau and Roux, and with DeGiuli et al. Our results confirm that the shear driven jamming transition in Bagnoldian systems is well described by a critical scaling theory (as was found previously for Newtonian systems), and we relate this scaling theory to the phenomenological constituent laws for dilatancy and friction.