An optical fiber based interferometer to measure velocity profiles in sheared complex fluids
- 25 February 2003
- journal article
- Published by EDP Sciences in The European Physical Journal Applied Physics
- Vol. 22 (2) , 143-154
- https://doi.org/10.1051/epjap:2003014
Abstract
We describe an optical fiber based interferometer to measure velocity profiles in sheared complex fluids using dynamic light scattering (DLS). After a review of the theoretical problem of DLS under shear, a detailed description of the setup is given. We outline the various experimental difficulties induced by refraction when using a Couette cell. We also show that homodyne DLS is not well suited to measure quantitative velocity profiles in narrow-gap Couette geometries. On the other hand, the heterodyne technique allows us to determine the velocity field inside the gap of a Couette cell. All the technical features of the setup, namely its spatial resolution (≈ 50 − 100 µm) and its temporal resolution (≈ 1 s per point, ≈ 1 min per profile) are discussed, as well as the calibration procedure with a Newtonian fluid. As briefly shown on oil-in-water emulsions, such a setup permits one to record both velocity profiles and rheological data simultaneously.Keywords
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