MRI evidence for a "coffee-front effect" in drying porous media

Emmanuel Keita (1) , Pamela Françoise Faure (2) , Stéphane Rodts (2) , Philippe Coussot (2)

1 navier umr 8205 - Laboratoire Navier
2 Physique des milieux poreux

After drying colloidal particles suspended in a porous medium a concentration gradient appears. Using 1H MRI we propose a protocol to observe simultaneously the distributions of air, liquid, and colloid through the unsaturated solid porous structure. Thus we show that the above phenomenon comes from a receding-front effect: The elements migrate towards the free surface of the sample and accumulate in the remaining liquid films. Our understanding of the process makes it possible to establish a simple model without diffusion predicting the drying rate and the concentration distribution in time, in excellent agreement with the experimental observations. © 2013 American Physical Society.

Domaines: Sciences de l'ingénieur [physics]; Mécanique [physics.med-ph]; Mécanique des solides [physics.class-ph]; Physique [physics]; Mécanique [physics]; Mécanique des solides [physics.class-ph]; Sciences de l'ingénieur [physics]; Mécanique [physics.med-ph]; Mécanique des matériaux [physics.class-ph]; Physique [physics]; Mécanique [physics]; Mécanique des matériaux [physics.class-ph]

Emmanuel Keita, Pamela Françoise Faure, Stéphane Rodts, Philippe Coussot. MRI evidence for a "coffee-front effect" in drying porous media. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, 2013, 87 (6), ⟨10.1103/physreve.87.062303⟩. ⟨hal-00946113⟩