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Patterns in flowing sand: understanding the physics of granular flow
Tamás Börzsönyi1, Robert E Ecke, Jim N McElwaine
1Research Institute for Solid State Physics and Optics, Post Office Box 49, H-1525 Budapest, Hungary. btamas@szfki.hu
Physical Review Letters
|November 13, 2009
Summary
Granular flows can become unstable, forming stripes. At high densities, these stripes resemble a boiling effect, similar to the Leidenfrost effect, with fast-moving regions over agitated material.
Area of Science:
- Physics
- Geophysics
- Fluid Dynamics
Background:
- Dense granular flows exhibit instabilities and inhomogeneous structures.
- Understanding flow instabilities is crucial, despite advances in simple flow analysis.
Purpose of the Study:
- Investigate the formation of longitudinal stripes in granular flows.
- Analyze the role of flow density in stripe formation and characteristics.
Main Methods:
- Experimental investigation of granular flow on a rough inclined plane.
- Numerical simulations to model flow dynamics and instability.
Main Results:
- Observed the emergence of longitudinal stripes from uniform granular flow instability.
- Demonstrated that stripe morphology is density-dependent.
- Identified a robust stripe pattern at high densities, featuring fast sliding plugs over agitated material, akin to the Leidenfrost effect.
Conclusions:
- The uniform flowing state of granular media on rough inclined planes is unstable.
- Flow density critically influences the resulting stripe patterns, with high-density flows exhibiting a unique Leidenfrost-like configuration.
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