Eur. Phys. J. AP
Volume 22, Number 2, May 2003
|Page(s)||143 - 154|
|Section||Physics and Mechanics of Fluids, Microfluidics|
|Published online||25 February 2003|
An optical fiber based interferometer to measure velocity profiles in sheared complex fluids
Centre de Recherche Paul Pascal, avenue Schweitzer,
33600 Pessac, France
Revised: 7 January 2003
Accepted: 9 January 2003
Published online: 25 February 2003
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.
PACS: 83.85.Ei – Optical methods; rheo-optics / 42.25.Fx – Diffraction and scattering / 83.85.Cg – Rheological measurements-rheometry
© EDP Sciences, 2003
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