Universal scaling of flow curves: comparison between experiments and simulations

TL;DR

This paper compares experimental and simulation data on yield stress materials, identifying why different scaling exponents are observed by analyzing measurement conditions and their relation to the jamming transition.

Contribution

It clarifies the sources of discrepancy in flow curve scaling exponents between experiments and simulations, linking measurement conditions to the observed differences.

Findings

Simulations are near the jamming transition with small amplitudes.

Experiments are performed far from the critical volume fraction and at large amplitudes.

Differences in measurement conditions explain the variation in scaling exponents.

Abstract

Yield stress materials form an interesting class of materials that behave like solids at small stresses, but start to flow once a critical stress is exceeded. It has already been reported both in experimental and simulation work that flow curves of different yield stress materials can be scaled with the distance to jamming or with the confining pressure. However, different scaling exponents are found between experiments and simulations. In this paper we identify sources of this discrepancy. We numerically relate the volume fraction with the confining pressure and discuss the similarities and differences between rotational and oscillatory measurements. Whereas simulations are performed in the elastic response regime close to the jamming transition and with very small amplitudes to calculate the scaling exponents, these conditions are hardly possible to achieve experimentally. Measurements are often performed far away from the critical volume fraction and at large amplitudes. We show that these differences are the underlying reason for the different exponents for rescaling flow curves.