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Stabilité de l'écoulement multicouche de films non newtoniens sur un plan incliné

Abstract : We study the stability of stratified Newtonian or non Newtonian fluids flow down an inclined plane. This problem is of interest in many applications such as simultaneous coating of multiple layers. One of the defects encountered in this process is the onset of instabilities which cause ripples responsible for the degradation of the coating uniformity. We focused on fluids obeying the Carreau model. This model accurately describes the rheological behavior of fluids like polymers suspensions and melts and is particularly suitable to free surface flow issues.
The first part is devoted to one layer case. Three complementary approaches have been used: an asymptotic approach considering a weakly non-Newtonian behavior in the limit of long waves, then a phenomenological approach in order to describe the instability mechanisms, and at last a numerical solution of the general case. A spectral Tau collocation method based on Tchebychev polynomials is used for the discretization of the generalized Orr-Summerfeld eigenvalue problem. We mainly focus on the effects of shear-thinning properties on the flow stability.
The work was extended by the study of two-layer film flows. We highlighted the influence of a shear-thinning rheology, surface tensions, viscosity and density stratification on the stability. We combined this study with an energy budget to explain the differences on the stability according to the parameters. We investigated the key role played by the shear stress at the interfaces to explain these phenomena and the influence of the shear-thinning properties on the different contributions of the energy balance.
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https://tel.archives-ouvertes.fr/tel-00256920
Contributor : Severine Millet <>
Submitted on : Monday, February 18, 2008 - 2:25:03 PM
Last modification on : Wednesday, July 8, 2020 - 12:42:05 PM
Long-term archiving on: : Thursday, May 20, 2010 - 7:02:00 PM

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  • HAL Id : tel-00256920, version 1

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Séverine Millet. Stabilité de l'écoulement multicouche de films non newtoniens sur un plan incliné. Mécanique [physics.med-ph]. INSA de Lyon, 2007. Français. ⟨tel-00256920⟩

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