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Forcing symmetry exchanges and flow reversals in turbulent wakes

Published online by Cambridge University Press:  14 September 2017

Diogo Barros Open the ORCID record for Diogo Barros [Opens in a new window] ,
Jacques Borée ,
Olivier Cadot Open the ORCID record for Olivier Cadot [Opens in a new window] ,
Andreas Spohn  and
Bernd R. Noack Open the ORCID record for Bernd R. Noack [Opens in a new window]
Diogo Barros
Affiliation:
Institut Pprime UPR-3346, CNRS – Université de Poitiers – ENSMA, Poitiers 86360, France
Jacques Borée
Affiliation:
Institut Pprime UPR-3346, CNRS – Université de Poitiers – ENSMA, Poitiers 86360, France
Olivier Cadot
Affiliation:
IMSIA, ENSTA–ParisTech/CNRS/CEA/EDF, Université Paris Saclay, Palaiseau 91762, France
Andreas Spohn
Affiliation:
Institut Pprime UPR-3346, CNRS – Université de Poitiers – ENSMA, Poitiers 86360, France
Bernd R. Noack
Affiliation:
LIMSI – CNRS UPR 3251, Campus Universitaire d’Orsay, Orsay 91405, France Institut für Strömungsmechanik, TU Braunschweig, Braunschweig 38108, Germany
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Abstract

Turbulent wakes past bluff bodies commonly present asymmetric flow states reminiscent of bifurcations in the laminar regime. Understanding the sensitivity of these states to flow forcing is crucial to the modelling and control of flow symmetry properties. In this study, the near wake of a rectangular bluff body in proximity to a wall is disturbed by the use of passive devices located between the model and the wall, upstream of the massive flow separation occurring at the blunt trailing edges. Due to the proximity to the boundary, the wake initially presents wall-normal asymmetry and a negative wall-normal pressure gradient along the base. The application of disturbances with variable size, however, sets flow symmetry along the wall-normal plane, leading to the intermittent spanwise wake reversals reported recently in the literature. A further increase in the size of perturbation suppresses wake switching, and wall-normal asymmetry is recovered, but with a positive wall-normal pressure gradient. The dynamical features of this bifurcation scenario can be retrieved using two coupled symmetry-breaking models for spanwise and wall-normal pressure gradients. This confirms the high sensitivity of the separated flow to external perturbations. More importantly, the results unify observations of the bluff-body wake topologies covered in previous investigations.

JFM classification

Nonlinear Dynamical Systems: Bifurcation Flow Control: Instability control Wakes/Jets: Wakes
Type
Rapids
Information
Journal of Fluid Mechanics , Volume 829 , 25 October 2017 , R1
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Copyright
© 2017 Cambridge University Press 

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