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The onset of three-dimensional centrifugal global modes and their nonlinear development in a recirculating flow over a flat surface

Article dans une revue avec comité de lecture
Auteur
CHERUBINI, Stefania
19097 Dipartimento di Ingegneria Meccanica e Gestionale [DIMEG]
DE PALMA, Pietro
19097 Dipartimento di Ingegneria Meccanica e Gestionale [DIMEG]
ALIZARD, Frédéric
ccROBINET, Jean-Christophe
134975 Laboratoire de Dynamique des Fluides [DynFluid]

URI
http://hdl.handle.net/10985/6867
DOI
10.1063/1.3500677
Date
2010
Journal
Physics of Fluids

Résumé

The three-dimensional stability dynamics of a separation bubble over a flat plate has been studied in both linear and nonlinear conditions. Using a global eigenvalue analysis, two centrifugal global modes are identified: an asymptotically unstable three-dimensional weakly growing mode which appears to be originated by a Rayleigh instability; a marginally stable three-dimensional steady mode which is originated by a convective Gortler instability. Direct numerical simulations show that both modes play a role in the route to transition toward the turbulent flow. A structural sensitivity analysis is used to investigate the mechanism of selection of the path toward transition when small perturbations are considered. Finally, a scenario of transition via Gortler modes breakdown is studied in detail, revealing the formation of trains of hairpin vortices in streamwise succession.

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  • Dynamique des Fluides (DynFluid)

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    Article dans une revue avec comité de lecture
    CHERUBINI, Stefania; DE PALMA, Pietro; ccROBINET, Jean-Christophe (Cambridge University Press (CUP), 2013)
    The present work provides an optimal control strategy, based on the nonlinear Navier–Stokes equations, aimed at hampering the rapid growth of unsteady finite-amplitude perturbations in a Blasius boundary-layer flow. A ...
  • Rapid path to transition via nonlinear localized optimal perturbations in a boundary-layer flow 
    Article dans une revue avec comité de lecture
    CHERUBINI, Stefania; DE PALMA, Pietro; BOTTARO, Alessandro; ccROBINET, Jean-Christophe (American Physical Society (APS), 2010)
    Recent studies have suggested that in some cases transition can be triggered by some purely nonlinear mechanisms. Here we aim at verifying such an hypothesis, looking for a localized perturbation able to lead a boundary-layer ...
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    Article dans une revue avec comité de lecture
    CHERUBINI, Stefania; DE PALMA, Pietro; ccROBINET, Jean-Christophe (Elsevier, 2014)
    We use direct numerical simulations in the presence of free-stream turbulence having different values of intensity, T u, and integral length scale, L, in order to determine which kind of structures are involved in the path ...
  • Optimal wave packets in a boundary layer and initial phases of a turbulent spot 
    Article dans une revue avec comité de lecture
    CHERUBINI, Stefania; BOTTARO, Alessandro; DE PALMA, Pietro; ccROBINET, Jean-Christophe (Cambridge University Press (CUP), 2010)
    The three-dimensional global optimal dynamics of a flat-plate boundary layer is studied by means of an adjoint-based optimization in a spatial domain of long – but finite – streamwise dimension. The localized optimal initial ...
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    Article dans une revue avec comité de lecture
    CHERUBINI, Stefania; DE PALMA, Pietro; BOTTARO, Alessandro; ccROBINET, Jean-Christophe (American Institute of Physics, 2011)
    The understanding of laminar-turbulent transition in shear flows has recently progressed along new paradigms based on the central role of nonlinear exact coherent states. We follow such paradigms to identify, for the first ...

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