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Article Dans Une Revue Journal de Physique III Année : 1991

Mesure par interférométrie laser du mouvement d'une particule proche d'une paroi

Y. Assou
  • Fonction : Auteur
A. Azouni
  • Fonction : Auteur
F. Feuillebois
  • Fonction : Auteur

Résumé

An experimental technique based on laser interferometry is used to obtain the displacement of a sphere towards a plane wall in a viscous fluid : it consists in inserting the sphere in an interferometric system, in such a way that the displacement of the sphere changes the state of interference. An important feature of the setup is that the shape, the roughness, and the positioning of the sphere in the optical path are relatively uncritical. The spheres used in the experiment are bearing balls, 4 and 5 ×10-3 m in diameter. The accuracy on the sphere displacement is of the order of 2 ×10-8 m. The interference signal is digitalized and stored in a microcomputer. The data are then processed to yield the friction coefficient fTzz of the sphere in its motion very close to the wall. The variation of fTzz with the non-dimensional gap ε (ratio of the gap to the sphere radius) show three regions: (i) One in which a is small but at least 10 times larger than the non-dimensional rugosity (ratio of the scale of rugosity to the sphere radius) ; there is then a very good agreement with the result valid for a smooth sphere fTzz = 1/ε from lubrication theory. (ii) When ε decreases to the order of the non-dimensional rugosity, the friction coefficient is then smaller than 1/ε. The technique thus opens a way to study the effects of rugosity in hydrodynamics. (iii) The technique allows to measure gaps of the order of 10-8 m and could thus be used in future studies of short ranges forces.

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Dates et versions

jpa-00248583 , version 1 (04-02-2008)

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Y. Assou, Denis Joyeux, A. Azouni, F. Feuillebois. Mesure par interférométrie laser du mouvement d'une particule proche d'une paroi. Journal de Physique III, 1991, 1 (2), pp.315-330. ⟨10.1051/jp3:1991125⟩. ⟨jpa-00248583⟩
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