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Comptes Rendus Physique
Volume 13, n° 9-10
pages 866-877 (novembre 2012)
Doi : 10.1016/j.crhy.2012.09.006
On the dynamical role of coherent structures in turbulence
Sur le rôle dynamique des structures cohérentes dans la turbulence
 

Nicholas T. Ouellette
Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT 06520, USA 

Abstract

The notion of coherent structures in fluid mechanics – distinguishable regions of the flow field that share common properties and are correlated in space and time – has played a significant role in characterizing and modeling turbulent flows. They have not yet, however, truly become predictive tools, in part because there is no universally accepted way of extracting coherent structures from the flow field. A wide range of types of structures have been suggested, but there has been comparatively little work done to determine their role in the flow dynamics, and therefore to discern which structures are useful for more than flow visualization. Here, I review several common types of coherent structures, both Eulerian and Lagrangian, with a focus on two-dimensional turbulence far from boundaries. I also discuss a framework for pinpointing the dynamical role of coherent structures based on spatial localization of the spectral properties of the flow. Future work on coherent structures should focus on defining structures that play clear roles in the turbulence dynamics.

The full text of this article is available in PDF format.
Résumé

La notion en mécanique des fluides de structures cohérentes, cʼest-à-dire des régions particulières de lʼécoulement corrélées spatialement et temporellement et qui partagent des propriétés similaires, a joué un rôle significatif dans la caractérisation et la modélisation des écoulements turbulents. Pour autant, ces structures ne sont pas considérées comme des outils prédictifs car, notamment, il nʼexiste pas de consensus sur la méthode permettant leur extraction de lʼécoulement. Il a été proposé une gamme étendue de types de structures, mais peu de travail a été fourni visant à caractériser leur rôle dans la dynamique du fluide, cantonnant donc ces structures à une caractérisation visuelle de lʼécoulement. Dans cet article, je me propose de rappeler lʼimportance de quelques unes de ces structures, aussi bien eulériennes que lagrangiennes, avec un intérêt particulier pour la turbulence bidimensionnelle loin des bords. Je discuterai aussi de lʼexistence dʼun cadre permettant de quantifier leur rôle dynamique en me basant sur la localisation spatiale des propriétés spectrales de lʼécoulement. Les études futures des structures cohérentes devront se concentrer à définir les structures qui jouent un rôle clair dans la dynamique de la turbulence.

The full text of this article is available in PDF format.

Keywords : Coherent structures, Turbulence, Fluid mechanics

Mots-clés : Structures cohérentes, Turbulence, Mécanique des fluides




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