Viscosity of cohesive granular flows.

Area of Science:

• Physics
• Materials Science

Background:

• Cohesive granular materials exhibit liquid-like flow, but momentum transport mechanisms are not well understood.
• Current models for cohesive granular viscosity are debated and largely phenomenological.

Purpose of the Study:

• To investigate the fundamental mechanisms governing momentum transport in cohesive granular materials.
• To develop a more accurate model for cohesive granular viscosity by exploring the role of inter-particle adhesion.

Main Methods:

• Utilized discrete element simulations to model plane shear flows of cohesive granular materials.
• Systematically varied the intensity of inter-particle adhesion to observe its effect on material viscosity.

Main Results:

• Identified two key dimensionless numbers related to adhesion that control granular material viscosity.
• Developed a new scaling law that accurately describes non-Newtonian viscosity variations and unifies existing models.
• Linked viscosity changes to adhesion-induced alterations in microstructure and contact networks.

Conclusions:

• Adhesion significantly impacts granular material rheology by modifying the contact network and momentum transport.
• Discovered two distinct modes of momentum transport, with adhesion influencing only the balanced contact force mode.
• The findings advance the understanding of rheological models for granular and other soft materials.