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Penetration and blown air effect in granular media
Raphaël Clément1, Sylvain Courrech du Pont, Mehdi Ould-Hamouda
1Laboratoire Matière et Systèmes Complexes, UMR CNRS-Université Paris Diderot, France.
Physical Review Letters
|March 17, 2011
Summary
Penetrating a capped cylinder into sand is easier than an open one, contrary to liquids. Trapped air fluidizes sand, reducing resistance for easier motion.
Area of Science:
- Physics
- Materials Science
- Fluid Dynamics
Background:
- Granular media like sand exhibit increasing resistance with depth.
- Unlike liquids, granular media typically oppose motion via solid friction.
- Non-thermal systems, such as sand, display unique physical behaviors.
Purpose of the Study:
- To investigate the counterintuitive penetration dynamics of top-capped versus open cylinders in granular media (sand).
- To compare the penetration behavior in sand with that observed in liquids.
- To elucidate the role of trapped air in modifying the resistance experienced during penetration.
Main Methods:
- Vertical penetration experiments were conducted using both top-capped and open cylinders in dense sand.
- Comparative analysis of penetration resistance in sand versus liquids was performed.
- Observation and analysis of the effect of trapped air escaping from the cylinder on sand fluidization.
Main Results:
- Penetration into sand is significantly easier with a top-capped cylinder compared to an open one.
- In contrast, a top-capped cylinder experiences greater resistance in liquids due to increased buoyancy.
- Escaping air from the capped cylinder fluidizes the sand, thereby reducing penetration resistance.
Conclusions:
- The behavior of granular media differs fundamentally from liquids regarding the effect of trapped air during penetration.
- Top-capped cylinders facilitate easier penetration in sand by fluidizing the medium.
- This finding highlights the unique physical properties of granular materials and their interaction with trapped air.
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