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Etude des structures longitudinales dans la couche limite laminaire et de leur lien avec la transition

Abstract : Streamwise elongated structures, called streaks, are observed in boundary layers exposed to significant levels of external perturbations. The effect of these streaks on the transition process is investigated in this thesis. The equations for the streaks' dynamics are obtained using the streamwise parabolic form of the Navier-Stokes equations. The numerical resolution is based on projection schemes associated to spectral spatial discretization. Simulations of a boundary layer subject to different external perturbations have been performed. The receptivity of the boundary layer is studied in detail for different inflow conditions : optimal vortices, single tip-vortex and two-dimensional turbulence fields. The breakdown of an isolated streak is investigated by linear stability anaysis and direct numerical simulation. The instability, characterised by a short streamwise wavelength, re-generates streamwise structures by non-linear interactions. The streak's breakdown is then characterised by the appearance of quasi-streamwise vortices following the meandering of the streak. This mechanism shows some similarities with the near-wall cycle of fully developed turbulent flows. In the last part, a model is proposed to mimic the streaks' dynamics in laminar boundary layers subject to free-stream turbulence. This empirical model is then applied to estimate the bypass transition position.
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https://tel.archives-ouvertes.fr/tel-00160727
Contributor : Damien Biau <>
Submitted on : Friday, July 6, 2007 - 7:39:17 PM
Last modification on : Tuesday, March 16, 2021 - 3:42:04 PM
Long-term archiving on: : Thursday, April 8, 2010 - 10:39:57 PM

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  • HAL Id : tel-00160727, version 1

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Damien Biau. Etude des structures longitudinales dans la couche limite laminaire et de leur lien avec la transition. Dynamique des Fluides [physics.flu-dyn]. Ecole nationale superieure de l'aeronautique et de l'espace, 2006. Français. ⟨tel-00160727⟩

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