title: Extra dissipation and flow uniformization due to elastic instabilities of shear-thinning polymer solutions in model porous media.
abstract: We study flows of hydrolized polyacrylamide solutions in two dimensional porous media made using microfluidics, for which elastic effects are dominant. We focus on semi-dilute solutions (0.1%-0.4%) which exhibit a strong shear thinning behavior. We systematically measure the pressure drop and find that the effective permeability is dramatically higher than predicted when the Weissenberg number is greater than about 10. Observations of the streamlines of the flow reveal that this effect coincides with the onset of elastic instabilities. Moreover, and importantly for applications, we show using local measurements that the mean flow is modified: it appears to be more uniform at high Weissenberg number than for Newtonian fluids. These observations are compared and discussed using pore network simulations, which account for the effect of disorder and shear thinning on the flow properties.
authors.affiliation: Univ. Bordeaux, CNRS , Solvay, Lab. LOF UMR5258, Pessac, France.
authors.forename: Anaïs
authors.initials: A
authors.lastname: Machado
authors.affiliation: Univ. Grenoble Alpes, CNRS , Lab. LRP UMR5520, F-38000 Grenoble, France.
authors.forename: Hugues
authors.initials: H
authors.lastname: Bodiguel
authors.affiliation: Univ. Bordeaux, CNRS , Solvay, Lab. LOF UMR5258, Pessac, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Beaumont
authors.affiliation: Univ. Bordeaux, CNRS , Solvay, Lab. LOF UMR5258, Pessac, France.
authors.forename: Gérald
authors.initials: G
authors.lastname: Clisson
authors.affiliation: ESPCI , SIMM UMR 7615, 11 rue Vauquelin, 75005 Paris, France.
authors.forename: Annie
authors.initials: A
authors.lastname: Colin