Rheological Regimes in Agitated Granular Media under Shear

Area of Science:

• Physics
• Rheology
• Granular Mechanics

Background:

• Granular media exhibit complex rheology, including Newtonian, yield stress, and shear thickening behaviors.
• Existing theoretical frameworks struggle to encompass the diverse flow regimes of agitated granular materials.
• Understanding granular rheology is crucial for various scientific and industrial applications.

Purpose of the Study:

• To develop a unified theoretical framework for agitated granular media.
• To identify key dimensionless parameters governing granular rheology.
• To propose a constitutive relation capturing all observed flow behaviors.

Main Methods:

• Experimental measurement of air-fluidized glass particle rheology across five orders of magnitude in shear rate.
• Comparison of fluidization-induced agitation with Brownian motion.
• Analysis of rheological data using dimensionless numbers.

Main Results:

• All rheological regimes of agitated granular media can be delineated by the Péclet number (Pe) and the shear-to-fluidization power ratio (Π).
• A novel constitutive relation is proposed that quantitatively and qualitatively captures all flow behaviors.
• The framework successfully unifies Newtonian, yield stress, and shear thickening regimes.

Conclusions:

• A unified framework based on Pe and Π effectively describes the rheology of agitated granular media.
• The proposed constitutive relation offers a comprehensive model for granular flow.
• This work advances the theoretical understanding of complex granular material behavior.