J. Phys. II France 6 (1996) 1639-1654
Tracer Dispersion in a Polymer Solution Flowing Through a Double Porosity Porous MediumA. Paterson1, A. d'Onofrio1, 2, C. Allain1, J.P. Hulin1, M. Rosen2 and C. Gauthier3
1 Laboratoire de Fluides, Automatique et Systèmes Thermiques URA CNRS 871, Bâtiment 502, Université Paris-Sud, 91405 Orsay Cedex, France
2 Grupo de Medios Porosos, Facultad de Ingenieria, Paseo Colon 850, 1063 Buenos Aires, Argentina
3 Laboratoire des Matériaux et Structures du Génie Civil UMR CNRS-LCPC 113, Parc Club de la Haute Maison, 77420 Champs-sur-Marne, France
(Received 30 April 1996, received in final form 29 July 1996, accepted 31 July 1996)
Experimental results on the dispersion of a tracer in a polymer solution flowing through a nonconsolidated packing of porous grains are reported. We use a scleroglucane solution with a shear viscosity decreasing as a power law of the shear-rate over a broad range: the characteristic exponent is varied between 0.40 and 0.77 by changing the polymer content. Porous grains of size m and internal porosity are obtained by grinding sintered glass beads of initial diameter m. Dispersion measurements use a saline tracer at Péclet numbers Pe between 0.7 and 700. At a constant Pe, the dispersivity (K being the longitudinal dispersion coefficient) increases with (by a factor of 6 between and around Pe = 10). At some Pe values, early arrival time effects are observed. The dispersivity also increases with Pe at all values in the range of transition from diffusive towards convective transport in grains. These results are assumed to be due to the non-Newtonian characteristics of the solution increasing the contrast both between low and high velocity flow paths and between the inside and the outside of the grains.
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