title: Local velocity measurements in the shear-thickening transition of dilute micellar solutions of surfactants.
abstract: Local velocimetry and rheometric measurements are performed on three dilute micellar solutions which undergo the shear-thickening transition. The three surfactants, namely, alkyltrimethyl ammonium bromide (C(n)TAB), all belong to the same family and only differ by the length of the aliphatic chain. Simultaneous ultrasonic velocimetry and rheometry recordings provide convincing evidence for a heterogeneous flow in the shear-thickening domain. A detailed analysis allows us to demonstrate surprisingly similar evolutions of the wall slip magnitude and of the apparent viscosity as well as subtle differences between the three systems. Together with the velocimetry results, the direct observation of the flow in the vorticity-velocity plane reveals that the shear-thickening transition is associated with the emergence of a three-dimensional unstable flow.
authors.affiliation: Laboratory of the Future, CNRS, Université Bordeaux I, Rhodia, 178 avenue du Dr Schweitzer, 33608 Pessac cedex, France.
authors.forename: Jalal
authors.initials: J
authors.lastname: Dehmoune
authors.forename: Sébastien
authors.initials: S
authors.lastname: Manneville
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Decruppe