Wicking in a powder.
P S Raux1, H Cockenpot, M Ramaioli
1PMMH, UMR 7636 du CNRS, ESPCI, 75005 Paris, France.
Langmuir : the ACS Journal of Surfaces and Colloids
|February 27, 2013
Summary
Wetting granular media requires a critical contact angle around 55°, less than for tubes. Polydispersity and pressure further influence this spontaneous liquid impregnation.
Area of Science:
- Physics
- Materials Science
- Fluid Dynamics
Background:
- Wicking, or spontaneous liquid uptake, is crucial in porous materials.
- Understanding liquid penetration in granular media is essential for various applications.
- Previous studies often focused on simpler geometries like tubes.
Purpose of the Study:
- To investigate the phenomenon of wicking in granular media.
- To determine the critical contact angle for spontaneous liquid impregnation in granular layers.
- To analyze the influence of polydispersity and pressure on wetting transitions.
Main Methods:
- Theoretical analysis of liquid behavior at the surface of granular layers.
- Modeling wicking in monodisperse and polydisperse granular systems.
- Investigating the role of contact angle and external pressure.
Main Results:
- The critical contact angle for monodisperse granular layers is approximately 55°.
- This critical angle is significantly lower than the 90° threshold for tube penetration.
- Polydispersity and applied pressure were found to alter the critical contact angle.
Conclusions:
- Liquid impregnation in granular media is geometrically more challenging than in tubes.
- The critical contact angle is a key parameter governing spontaneous wetting in granular systems.
- Wetting behavior in granular media is sensitive to particle size distribution and external pressure.
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