Inertial shear flow of assemblies of frictionless polygons: Rheology and microstructure

Area of Science:

• Physics
• Materials Science
• Computational Mechanics

Background:

• Understanding shape effects in granular materials is crucial for predicting macroscopic behavior.
• Anisotropic particle shapes, like pentagons, can lead to different microstructural arrangements and flow properties compared to isotropic shapes, such as disks.

Purpose of the Study:

• To numerically investigate the macroscopic and microstructural properties of dense assemblies of frictionless polydisperse rigid pentagons in shear flow.
• To compare the behavior of pentagonal assemblies with similar systems of disks under varying inertial numbers.
• To analyze rheology and microstructure in uniform steady states.

Main Methods:

• Numerical simulations of dense granular assemblies.
• Application of shear flow to systems of frictionless polydisperse rigid pentagons and disks.
• Investigation across a range of inertial numbers (I), from quasistatic to 0.2.
• Analysis of macroscopic friction angle and solid fraction.

Main Results:

• Both pentagonal and disk systems flow at random close packing density without Reynolds dilatancy in the quasistatic limit.
• Pentagons show larger friction angles and solid fractions than disks at low inertial numbers, with differences diminishing at higher I.
• Contact networks deplete slower in pentagons, maintaining anisotropic force-transmitting structures; force anisotropy dominates shear strength at low I, while contact anisotropy dominates at higher I.

Conclusions:

• Particle shape significantly impacts granular material rheology and microstructure under shear flow.
• Force transmission mechanisms differ between pentagonal and disk assemblies, with shape anisotropy playing a key role.
• The study provides insights into how non-spherical particle shapes influence the mechanical response of granular media.