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Home page > Séminaires > Archives séminaires > Séminaires 2019 > Séminaire MSC. 18 février 2019. Jorge Peixinho (PIMM, ENSAM) : "Rotating and stretching viscoelastic fluids"..

Séminaire MSC. 18 février 2019. Jorge Peixinho (PIMM, ENSAM) : "Rotating and stretching viscoelastic fluids".

Sauf mention contraire, les séminaires et les soutenances se déroulent à 11h30 en salle 454A du bâtiment Condorcet.

Rotating and stretching viscoelastic fluids

Jorge Peixinho, Laboratoire PIMM - Procédés et Ingénierie en Mécanique et Matériaux - CNRS, Arts et Métiers (ENSAM) et CNAM, Paris

Abstract :

Liquids with complex structures, such as macromolecular solutions or melts, soap solutions or suspensions behave in unexpected ways. Here, we consider instabilities of viscoelastic solutions in rotating and stretching flows. Specifically, mixtures of relatively short and long linear polymers (polyethylene oxide) solutions in dilute and semi-dilute concentrations are first sheared between concentric cylinders, with the inner rotating and the outer fixed. The torque on the inner cylinder is modified compared to a Newtonian fluid of the same viscosity revealing the different flow patterns that emerge above the stability threshold for circular Couette flow. For large polymer concentrations, steady solitary pairs of vortices, were observed depending on the deceleration. Then, when the same polymer solutions are stretched between two horizontal plates, persistent filaments are formed depending on the balance between capillary, viscoelastic and inertial effects. We used a high-speed camera and a laser to extract properties of the solutions such as relaxation times and extensional viscosities. Moreover, the filament thinning experiences an instability where the filament’s morphology close to breakup is drops interconnected that endure drop migration, oscillation, and merging.

Contact : Équipe séminaires / Seminar team - Published on / Publié le 23 janvier 2019

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