Eur. Phys. J. Appl. Phys.
Volume 39, Number 3, September 2007
|Page(s)||267 - 274|
|Section||Physics and Mechanics of Fluids, Microfluidics|
|Published online||12 July 2007|
Influence of the disorder on solute dispersion in a flow channel
Grupo de Medios Porosos, Facultad de Ingeniería, Universidad de Buenos Aires, Paseo Colón 850, 1063 Buenos Aires, Argentina
2 Laboratoire Fluides, Automatique et Systèmes Thermiques, UMR No. 7608, CNRS, Universités Paris 6 et 11, Bâtiment 502, Campus Paris Sud, 91405 Orsay Cedex, France
Corresponding author: firstname.lastname@example.org
Accepted: 12 June 2007
Published online: 12 July 2007
Solute dispersion is studied experimentally in periodic or disordered arrays of beads in a capillary tube. Dispersion is measured from light absorption variations near the outlet following a steplike injection of dye at the inlet. Visualizations using dye and pure glycerol are also performed in similar geometries. Taylor dispersion is dominant both in an empty tube and for a periodic array of beads: the dispersivity ld increases with the Péclet number Pe respectively as Pe and Pe0.82 and is larger by a factor of 8 in the second case. In a disordered packing of smaller beads (1/3 of the tube diameter) geometrical dispersion associated to the disorder of the flow field is dominant with a constant value of ld reached at high Péclet numbers. The minimum dispersivity is slightly higher than in homogeneous nonconsolidated packings of small grains, likely due to wall effects. In a weakly disordered packing with the same beads as in the periodic configuration, ld is up to 20 times lower than in the latter and varies as Peγ with γ = 0.5 or = 0.69 (depending on the fluid viscosity). A simple model accounting for this latter result is suggested.
PACS: 47.56.+r – Flows through porous media / 05.60.Cd – Classical transport
© EDP Sciences, 2007
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