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Universal and wide shear zones in granular bulk flow
Denis Fenistein1, Jan Willem van de Meent, Martin van Hecke
1Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands.
Physical Review Letters
|April 20, 2004
Summary
Experiments reveal that slow granular flows in a split-bottomed Couette geometry create wide shear zones. These zones expand with layer height, following a universal scaling law and error function velocity profile.
Area of Science:
- Rheology of granular materials
- Fluid dynamics of non-Newtonian flows
Background:
- Understanding granular flow is crucial in various industrial and geological processes.
- Traditional Couette geometries often confine shear zones to sidewalls, limiting study.
- Characterizing shear zone behavior in granular materials remains a challenge.
Purpose of the Study:
- To investigate the formation and scaling of shear zones in slow granular flows.
- To analyze the universality of velocity profiles within these shear zones.
- To explore the influence of layer height on shear zone dynamics.
Main Methods:
- Utilizing a modified split-bottomed Couette rheometer for granular flow experiments.
- Systematically varying granular layer heights.
- Measuring and analyzing velocity profiles across the shear zones.
Main Results:
- Identified wide, tunable shear zones forming away from sidewalls.
- Observed shear zone width increasing with layer height, following a particle-independent scaling law.
- Demonstrated that rescaled velocity profiles collapse onto a universal error function master curve.
Conclusions:
- The split-bottomed Couette geometry effectively creates and studies large-scale shear zones in granular flows.
- Granular shear zone dynamics exhibit universal scaling behavior independent of particle properties.
- The error function accurately describes the velocity profile within these granular shear zones.
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