Rheology of a 2D granular film

Area of Science:

• Soft Matter Physics
• Fluid Dynamics
• Granular Materials Science

Background:

• Particle-laden fluid interfaces present complex rheological behaviors.
• Understanding granular flow in confined geometries is crucial for various applications.

Purpose of the Study:

• To experimentally investigate the rheology of macroscopic particle-laden soap films (Granular Films) under simple shear.
• To explore the relationship between macroscopic rheological measurements and particle-scale interactions.
• To elucidate the non-local rheological behavior of Granular Films.

Main Methods:

• Simultaneous macroscopic rheological measurements using a classical rheometer.
• Particle-scale interaction analysis via an overhead camera to determine grain velocity fields.
• Experimental setup involving macroscopic particles bridging both fluid interfaces of a soap film.

Main Results:

• Observed inhomogeneous shear within the Granular Film, with a highly-sheared zone near the moving wall.
• Identified a large quasistatic area contrasting with the sheared zone, indicating non-local rheology.
• Correlated macroscopic stress components with the observed shear behavior.

Conclusions:

• Granular Films exhibit non-local rheological properties analogous to dry granular materials.
• The observed shear localization is explained by extended kinetic theory.
• A transition in the dominant stress component contributes to the material's behavior.