Granular dynamics of a slurry in a rotating drum

Area of Science:

• Physics of granular materials
• Fluid dynamics
• Rheology

Background:

• Granular flow in rotating drums is a fundamental problem in physics.
• Understanding the influence of interstitial fluids on granular dynamics is crucial.
• Previous studies have explored different flow regimes, but the role of fluid viscosity requires further investigation.

Purpose of the Study:

• To investigate the effect of interstitial fluid viscosity on the dynamics of granular flow.
• To determine how viscosity influences bead speed and mixing rates.
• To explore the transition between inertial and viscous flow regimes.

Main Methods:

• Experiments were conducted using a thin rotating drum half-filled with monodisperse glass beads.
• The rotating speed was fixed in the rolling regime, ensuring a continuous flowing layer.
• Fluid viscosity was systematically varied to observe its effects on dynamical processes.

Main Results:

• Bead speed in the flowing layer decreased as fluid viscosity (μ) increased.
• The mixing rate of beads was observed to increase with higher fluid viscosity.
• A simple model relating flow layer thickness to viscosity was found to be consistent with the findings.

Conclusions:

• Interstitial fluid viscosity plays a significant role in granular flow dynamics.
• Increased viscosity leads to slower bead movement but enhanced mixing.
• Results suggest a potential transition from inertial to viscous regimes with decreasing Stokes number.