The linear secondary stability of large-scale optimal streaks in turbulent Couette flow at and Poiseulle flow at is investigated. The streaks are computed by solving the nonlinear two-dimensional Reynolds-averaged Navier–Stokes equations using an eddy-viscosity model. Optimal initial conditions leading the largest linear transient growth are used, and as the amplitude of the initial vortices increases, the amplitude of streaks gradually increases. Instabilities of the streaks appear when their amplitude exceeds approximately of the velocity difference between walls in turbulent Couette flow and of the centerline velocity in turbulent Poiseuille flow. When the amplitude of the streaks is sufficiently large, the instabilities attain significant growth rates in a finite range of streamwise wavenumbers that shows good agreement with the typical streamwise wavenumbers of the large-scale motions in the outer region.
L'instabilité linéaire secondaire des streaks à grande échelle est étudiée dans les écoulements de Couette turbulent à et Poiseuille turbulent à . Les streaks sont calculés en résolvant les équations de Navier–Stokes moyennées selon Reynolds en utilisant un modèle de viscosité turbulente. Les conditions initiales optimales, induisant la plus grande croissance transitoire, sont utilisées ; quand l'amplitude des tourbillons optimaux initiaux est augmentée, l'amplitude des streaks augmente aussi. Les streaks deviennent instables quand leur amplitude est supérieure à environ de la différence de vitesse entre les deux parois dans l'écoulement de Couette turbulent et de la vitesse au centre du canal dans l'écoulement de Poiseuille turbulent. Quand l'amplitude des streaks est suffisamment élevée les instabilités atteignent des taux d'amplification significatifs dans une bande de longueurs d'onde qui est en bon accord avec les longueurs d'onde typiques observées dans les région externe.
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Mots-clés : Instabilité, Instabilité secondaire, Streaks à grande échelle, Écoulements turbulent
Junho Park 1; Yongyun Hwang 1; Carlo Cossu 2, 3
@article{CRMECA_2011__339_1_1_0, author = {Junho Park and Yongyun Hwang and Carlo Cossu}, title = {On the stability of large-scale streaks in turbulent {Couette} and {Poiseulle} flows}, journal = {Comptes Rendus. M\'ecanique}, pages = {1--5}, publisher = {Elsevier}, volume = {339}, number = {1}, year = {2011}, doi = {10.1016/j.crme.2010.10.012}, language = {en}, }
TY - JOUR AU - Junho Park AU - Yongyun Hwang AU - Carlo Cossu TI - On the stability of large-scale streaks in turbulent Couette and Poiseulle flows JO - Comptes Rendus. Mécanique PY - 2011 SP - 1 EP - 5 VL - 339 IS - 1 PB - Elsevier DO - 10.1016/j.crme.2010.10.012 LA - en ID - CRMECA_2011__339_1_1_0 ER -
Junho Park; Yongyun Hwang; Carlo Cossu. On the stability of large-scale streaks in turbulent Couette and Poiseulle flows. Comptes Rendus. Mécanique, Volume 339 (2011) no. 1, pp. 1-5. doi : 10.1016/j.crme.2010.10.012. https://comptes-rendus.academie-sciences.fr/mecanique/articles/10.1016/j.crme.2010.10.012/
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