Size-dependence of the flow threshold in dense granular materials
1School of Engineering, Brown University, Providence, RI, USA. david_henann@brown.edu.
Soft Matter
|June 15, 2018
Summary
Granular material flow depends on system size, with smaller systems requiring more force to initiate flow. A new model accurately predicts this size-dependent strengthening across various flow types.
Area of Science:
- Physics
- Engineering
- Materials Science
Background:
- Dense granular material flow is often modeled using local, stress-based criteria.
- Grain-scale cooperativity causes size effects not captured by local models, such as thinner layers needing more tilt to flow on inclined planes.
Purpose of the Study:
- To investigate if the size-dependence of the flow threshold in inclined plane flow is general across different inhomogeneous flow configurations.
- To validate a nonlocal continuum model's ability to capture these size effects.
Main Methods:
- Utilized two-dimensional discrete-element method (DEM) calculations.
- Simulated three distinct inhomogeneous flow scenarios: planar shear flow with gravity, annular shear flow, and vertical chute flow.
Main Results:
- Demonstrated that the flow threshold is size-dependent in all three simulated configurations.
- Observed additional strengthening as the system size was reduced in each case.
Conclusions:
- The size-dependence of the flow threshold is a general phenomenon in dense granular materials across various flow types.
- The nonlocal granular fluidity model quantitatively captures the observed size-dependent strengthening in all tested configurations.
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