Comptes Rendus
no. 12
Experimental observation of frequency doubling in a viscoelastic mixing layer
[Observation expérimentale de doublement de fréquence dans la couche de mélange viscoélastique.]

Présenté par : Patrick Huerre

F. Sausset1  ; O. Cadot1  ; S. Kumar2
1 Physique et mécanique des milieux hétérogènes, École supérieure de physique et de chimie industrielle, 10, rue Vauquelin, 75231 Paris cedex, France
2 Department of Chemical Engineering and Materials Science, University of Minnesota, 151 Amundson Hall, 421 Washington Ave. SE, Minneapolis, MN 55455, USA
Comptes Rendus. Mécanique, Volume 332 (2004) no. 12, pp. 1001-1006.

Une étude expérimentale de la couche de mélange à un nombre de Reynolds de 440 est réalisée. Une solution viscoélastique colorée est introduite dans la couche cisaillée stationnaire juste avant la formation des tourbillons. En utilisant un mesure locale de la vitesse et une technique de visualisation par fluorescence, il est montré que la formation tourbillonnaire est affectée par le comportement non-Newtonien de la solution viscoélastique par rapport au cas Newtonien. Cet effet correspond à la formation de tourbillons secondaires produisant un harmonique supérieur dans la répartition spatiale de vorticité. En conséquence, un doublement de la fréquence des oscillations de la vitesse locale dans la couche de mélange est observé.

An experimental mixing layer in water at Reynolds number 440 is investigated. A colored viscoelastic solution is introduced in the shear layer before the roll-up dynamics. On the basis of flow visualization and local velocity measurements, it is found that compared to the Newtonian case, the roll-up process is affected by the non-Newtonian behavior of the viscoelastic solution. The effect consists of the appearance of secondary eddies in the mixing layer corresponding to the production of higher harmonics in the vorticity distribution. Consequently, there is a frequency doubling of the local velocity oscillations in the mixing layer.

Reçu le :
Accepté le :
Publié le :
DOI : 10.1016/j.crme.2004.10.001
Keywords: Fluid mechanics, Mixing layer, Elasticity, Harmonic production
Mot clés : Mécanique des fluides, Couche de mélange, Élasticité, Production d'harmoniques
F. Sausset 1 ; O. Cadot 1 ; S. Kumar 2

1 Physique et mécanique des milieux hétérogènes, École supérieure de physique et de chimie industrielle, 10, rue Vauquelin, 75231 Paris cedex, France
2 Department of Chemical Engineering and Materials Science, University of Minnesota, 151 Amundson Hall, 421 Washington Ave. SE, Minneapolis, MN 55455, USA 
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F. Sausset; O. Cadot; S. Kumar. Experimental observation of frequency doubling in a viscoelastic mixing layer. Comptes Rendus. Mécanique, Volume 332 (2004) no. 12, pp. 1001-1006. doi : 10.1016/j.crme.2004.10.001. https://comptes-rendus.academie-sciences.fr/mecanique/articles/10.1016/j.crme.2004.10.001/

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