Fluidization of wet granulates under shear

Area of Science:

• Physics
• Materials Science
• Fluid Dynamics

Background:

• Wetting liquids, such as water, create capillary bridges between granular materials like sand, imparting cohesion and stiffness.
• These capillary forces enable wet sand to transition from a solidified to a fluidized state when subjected to external shear forces.

Purpose of the Study:

• To investigate the transition dynamics between arrested (solid) and fluidized states in wet granular materials.
• To model the role of capillary bridges in the mechanical behavior of wet sand under shear.

Main Methods:

• Utilized molecular dynamics (MD)-type simulations of a 2D assembly of bidisperse frictionless disks.
• Incorporated a hysteretic, short-range attractive force to model capillary bridge effects alongside soft-core repulsion.
• Applied a cosine force profile to simulate external shear forces and explored a range of densities.

Main Results:

• The transition between fluidized and arrested states was found to be discontinuous and hysteretic.
• The critical force for solidification was analyzed, showing parameter dependence across various densities.
• The study explored system behavior approaching shear-banded states.

Conclusions:

• The hysteretic nature of capillary forces dictates a discontinuous transition in wet granular materials.
• The findings provide insights into the fundamental mechanics of wet granular matter and its transition behaviors.
• Comparisons were drawn between this transition and the jamming transition in granular systems.