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Low-order modelling of the wake dynamics of an Ahmed body

Published online by Cambridge University Press:  01 October 2021

Bérengère Podvin Open the ORCID record for Bérengère Podvin [Opens in a new window] ,
Stéphanie Pellerin Open the ORCID record for Stéphanie Pellerin [Opens in a new window] ,
Yann Fraigneau Open the ORCID record for Yann Fraigneau [Opens in a new window] ,
Guillaume Bonnavion Open the ORCID record for Guillaume Bonnavion [Opens in a new window]  and
Olivier Cadot Open the ORCID record for Olivier Cadot [Opens in a new window]
Bérengère Podvin*
Affiliation:
Université Paris-Saclay, CNRS, Laboratoire interdisciplinaire des sciences du numérique, 91405, Orsay, France
Stéphanie Pellerin
Affiliation:
Université Paris-Saclay, CNRS, Laboratoire interdisciplinaire des sciences du numérique, 91405, Orsay, France
Yann Fraigneau
Affiliation:
Université Paris-Saclay, CNRS, Laboratoire interdisciplinaire des sciences du numérique, 91405, Orsay, France
Guillaume Bonnavion
Affiliation:
Institut Pprime, UPR CNRS 3346, ISAE-ENSMA, Fluides Thermique Combustion, 86961Futuroscope-Chasseneuil, France
Olivier Cadot
Affiliation:
School of Engineering, University of Liverpool, LiverpoolL69 3GH, UK
*
†Email address for correspondence: podvin@limsi.fr
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Abstract

We investigate the large-scale signature of the random switches between two mirrored turbulent wake states of flat-backed bodies. A direct numerical simulation (DNS) of the flow around an Ahmed body at a Reynolds number ($Re$) of 10 000 is considered. Using proper orthogonal decomposition (POD), we identify the most energetic modes of the velocity field and build a low-dimensional model based on the first six fluctuating velocity modes capturing the characteristics of the flow dynamics during and between switches. In the absence of noise, the model produces random switches with characteristic time scales in agreement with the simulation and experiments. This chaotic model suggests that random switches are triggered by the increase of the vortex shedding activity. However, the addition of noise results in a better agreement in the temporal spectra of the coefficients between the model and the simulation.

JFM classification

Nonlinear Dynamical Systems: Low-dimensional models Wakes/Jets: Wakes
Type
JFM Rapids
Information
Journal of Fluid Mechanics , Volume 927 , 25 November 2021 , R6
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Copyright
© The Author(s), 2021. Published by Cambridge University Press

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References

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