Sommaire:

Viscoelastic fluids exhibit an intermediate behavior between elastic solids and dissipative liquids, depending on the time scale at which they are perturbed. Elastic instabilities may occur in the flow of viscoelastic fluids and a general criterion for the onset of these instabilities can be established based on the curvature of flow streamlines and fluid elasticity.
I will present in this talk an overview of the experimental work that I have performed on the characterization of the onset of elastic flow instabilities in viscoelastic (polymeric or wormlike micellar) solutions in different flow geometries (ranging from microfluidic to macroscopic devices), and for different flow protocols.
By performing oscillatory shear experiments in a cone-plate configuration we showed that, for large enough amplitudes of the driving, the homogeneous flow became unstable and it reorganized into different stable shear bands. Similarly, in oscillatory pipe flow the laminar flow became unstable leading to the formation of viscoelastic vortex rings. In steady flows, experiments performed in microfluidic serpentine channels allowed us to determine the influence of shear-thinning on the onset of purely elastic instabilities. Furthermore, we characterized an elastically-driven turbulent flow regime, which displayed anomalous scaling properties.

Pour plus d'informations, merci de contacter Massiera G.