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L'instabilité de Saffman-Taylor dans les fluides complexes : relation entre les propriétés rhéologiques et la formation de motifs

Abstract : We study the Saffman-Taylor instability in complex fluids. More precisely, we study the relation between rheological properties and pattern formation in a Hele-Shaw cell. To do so, we use model fluids, having only one non-Newtonian property at a time. A rheological study shows that the dominant property of a solution of the rigid polymer Xanthane is the shear thinning viscosity, that a solution of the flexible polymer PEO exhibits normal stresses and that a polymer gel exhibits a yield stress. For classical fluids, the relative width of the Saffman-Taylor fingers is determined by the ratio of the viscous forces to the capillary forces. In the case of a shear thinning fluid, the viscous forces are altered, leading to a narrowing of the finger. A modification of the viscous stresses by the existence of a yield stress leads to very branched patterns with a characteristic finger width, that is a function of the yield stress. For an elastic fluid, the normal stresses exert an extra pressure on the finger, which is added to the capillary forces and leads to finger widening. The knowledge of the influence of each of this properties separately on the Saffman-Taylor instability, constitutes a basis for studying the instability in even more complex fluids. The studied properties are among the most frequently encountered non-Newtonian properties allowing for a better understanding of the instability in fluids that exhibit several non-Newtonian properties simultaneously.
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Submitted on : Tuesday, January 8, 2002 - 4:02:45 PM
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  • HAL Id : tel-00000960, version 1

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Anke Lindner. L'instabilité de Saffman-Taylor dans les fluides complexes : relation entre les propriétés rhéologiques et la formation de motifs. Dynamique des Fluides [physics.flu-dyn]. Université Pierre et Marie Curie - Paris VI, 2000. Français. ⟨tel-00000960⟩

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