Berlin 2015 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 39: Flow-Induced Structures in Complex Fluids (joint session CPP/ DRG, Deutsche Rheologische Gesellschaft/ DY)
DY 39.11: Talk
Wednesday, March 18, 2015, 18:00–18:15, C 264
Evidence for simultaneous appearance of gradient and vorticity shear bands using time-resolved Rheo-SANS and laser light transmittance measurements — •Annekathrin Mütze1, Peggy Heunemann1, Lionel Porcar2, and Peter Fischer1 — 1ETH Zürich, Schmelzbergstr. 9, 8092 Zürich, Switzerland — 2Institute Laue-Langevin, 6 rue Jules Horowitz, B.P.156, F-38042 Grenoble Cedex 9, France
The flow properties of wormlike micellar surfactant solutions play an important role in applications like drag reduction in turbulent flows, fracturing fluids, and encapsulation agents. Such systems are studied with respect to the applied shear stress, concentration, temperature and composition of the salt counter ions. A combination of rheological measurements, laser-light transmittance, video analysis, and rheo-small angle neutron scattering allow a detailed exploration of number and types of shear bands. Typical flow curves of the solutions show Newtonian, shear-thinning, and shear-thickening flow behavior. In the latter regime, the solutions show vorticity and gradient shear bands simultaneously, in which vorticity shear bands dominate the visual effect, while gradient shear bands always coexist and predominate the rheological response. We show that gradient shear bands change their phases (turbid, clear) with the same frequency as the shear rate oscillates, whereas in-time vorticity shear bands change their phases with half the frequency of the shear rate [1].
[1] A. Mütze, P. Heunemann, P. Fischer. Journal of Rheology 58(6): 1647