Large Eddy Simulations of a constant-density flow carrying a passive scalar around a square cylinder at Reynolds numbers and are performed. We describe the three-dimensional topology of the turbulent flow in terms of intense longitudinal counter-rotating coherent vortices. We show also a change of regime concerning spanwise Kelvin–Helmholtz (KH) vortices. At the lower Reynolds number, they roll up downstream of the obstacle to form the von Kármán vortex street (VK). At higher Reynolds, they form immediately in the separating shear layer on the two sides of the cylinder. The role of vortices in the passive-scalar mixing is also looked at.
Nous présentons des résultats de Simulations des Grandes Echelles d'un écoulement de densité uniforme transportant un scalaire passif autour d'un cylindre de section carrée à nombre de Reynolds et . Nous décrivons la topologie tri-dimensionnelle de l'écoulement turbulent sous forme de tourbillons cohérents longitudinaux intenses contrarotatifs. Nous montrons aussi un changement de régime affectant les tourbillons de Kelvin–Helmholtz (KH) transverses. A bas Reynolds, ils se forment en aval de l'obstacle pour constituer l'allée de von Kármán (VK). A haut Reynolds, ils se forment immédiatement dans la couche cisaillée décollée sur les deux parois du cylindre. Le rôle des tourbillons dans le mélange du scalaire passif est aussi étudié.
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Mots-clés : Mécanique des fluides numérique, Simulation des Grandes Echelles, Turbulence, Sillage de cylindre, Tourbillons longitudinaux, Mélange de scalaire passif
Christophe Brun 1, 2; Thomas Goossens 2
@article{CRMECA_2008__336_4_363_0, author = {Christophe Brun and Thomas Goossens}, title = {3D coherent vortices in the turbulent near wake of a square cylinder}, journal = {Comptes Rendus. M\'ecanique}, pages = {363--369}, publisher = {Elsevier}, volume = {336}, number = {4}, year = {2008}, doi = {10.1016/j.crme.2008.01.002}, language = {en}, }
Christophe Brun; Thomas Goossens. 3D coherent vortices in the turbulent near wake of a square cylinder. Comptes Rendus. Mécanique, Volume 336 (2008) no. 4, pp. 363-369. doi : 10.1016/j.crme.2008.01.002. https://comptes-rendus.academie-sciences.fr/mecanique/articles/10.1016/j.crme.2008.01.002/
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