Evidence for three-dimensional unstable flows in shear-banding wormlike micelles.
We report on an experimental study of the shear-banding phenomenon in the concentrated wormlike micellar system CTAB at 20wt.% in D2O . Time-resolved velocity profiles are recorded using ultrasonic velocimetry simultaneously to global rheological data. Our results confirm the studies performed previously by Fischer and Callaghan [Phys. Rev. E 64, 011501 (2001)]. Time averaged velocity profiles display an unsheared "nematic gel." In the range of applied shear rate, the flow field exhibits very fast temporal fluctuations. Suspicions for the presence of three-dimensional flow are evidenced and possible causes for a three-dimensional instability are discussed together with the coupling of wall slip to bulk dynamic.
Centre de Recherche Paul Pascal, Avenue Schweitzer, 33600 Pessac, France. Lydiane.Becu@univ-lemans.fr
Lydiane
L
Bécu
Domitille
D
Anache
Sébastien
S
Manneville
Annie
A
Colin