title: Azimuthal instability of the interface in a shear banded flow by direct visual observation.
abstract: The stability of the shear banded flow of a Maxwellian fluid is studied from an experimental point of view using rheology and flow visualization with polarized light. We show that the one-layer homogeneous flow cannot sustain shear rates corresponding to the end of the stress plateau. The high shear rate branch is not found and the shear stress oscillates at the end of the plateau. An azimuthal instability appears: the shear induced band becomes unstable and the interface between the two bands undulates in time and space with a period τ, a wavelength λ and a wave vector k parallel to the direction of the tangential velocity.
authors.affiliation: Laboratoire de Physique des Milieux Denses Université Paul Verlaine Metz 1, Bld D.Arago F-57078 Metz cedex 3, France. Decruppe@univ-mezt.fr
authors.forename: J P
authors.initials: JP
authors.lastname: Decruppe
authors.forename: L
authors.initials: L
authors.lastname: Bécu
authors.forename: O
authors.initials: O
authors.lastname: Greffier
authors.forename: N
authors.initials: N
authors.lastname: Fazel
mesh_terms: D008027:Light; D008954:Models, Biological; D019370:Observation; D012212:Rheology / Q000379:methods*; D013314:Stress, Mechanical; D013997:Time Factors; D014741:Video Recording; D014783:Viscosity