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3D optimal perturbations developing in homogeneous mixing layers in presence of subharmonic vortex-pairing

Lopez-Zazueta, Adriana and Joly, Laurent and Fontane, Jérôme 3D optimal perturbations developing in homogeneous mixing layers in presence of subharmonic vortex-pairing. (2012) In: 65th Annual Meeting of the American Physical Society's Division of Fluid Dynamics (DFD), 18 November 2012 - 20 November 2012, San Diego, United States (United States). (Unpublished)

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Many experimental and numerical studies have found that the pairing of primary Klevin-Helmholtz (KH) vortices in mixing layers generally inhibits the growth of infinintesimal three-dimensional disturbances, delaying the transition to turbulence. In this work, we investigate the existence of 3D perturbations that grow fast enough to survive the subharmonic merging instability. For this purpose, we perform a numerical study of the transient linear evolution of 3D perturbations emerging in a homogeneous time-evolving mixing layer which undergoes pairing. We look at the optimal perturbation that yields the largest gain of energy at a specific time horizon, by use of an optimization method which solves iteratively the linearized direct and adjoint Navier-Stokes equations. In particular, we consider the influence of the time horizon relative to the saturation time of both the primary KH and subharmonic pairing instabilities.

Item Type:Conference or Workshop Item (Lecture)
Audience (conference):International conference without published proceedings
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Institution:Université de Toulouse > Institut Supérieur de l'Aéronautique et de l'Espace - ISAE-SUPAERO (FRANCE)
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Deposited On:24 Jan 2013 10:32

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