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Theses

Analyse expérimentale d'un modèle de tourbillon conique et de sa sensibilité à une turbulence amont

Abstract : The experimental research presented in this thesis aims to study the influence of an upstream flow with and without free stream turbulence (FST) on conical vortices (primary and secondary) generated from a A-pillar strut. This flow configuration is encountered on land vehicles and the interaction of the A-pillar vortices with the side windows is the main contributor to aerodynamic noise transmitted in the car. A model of dihedral type was designed and tested in a wind tunnel in order to generate these vortices. Spatial and temporal properties of velocity and wall pressure fields were studied using simultaneously PIV (or stereo-PIV) measurements and fluctuating wall pressure measurements using off-set sensors. It has been shown that moderate free-stream turbulence (intensity : 4%) leads to a very important modification of the shape of the A-pillar vortex and of the resulting wall pressure field (Cp'). Our conjecture - based on the study of statistical moments and spatio-temporal correlations - is that without FST, the main contribution to Cp' is linked to the local contribution of the 3D vortex core and induced separation. On the contrary, Cp', in presence of FST, seems to be associated with a global response of the 3D separation and induced aerodynamic field around the body. The difference observed with and without FST in the pressure and velocity fields have a significant impact on the Cp' and means that these contributions might be transmitted in very different ways by the car structure because the frequency and length scale range are very distinct. The inclusion of simple geometric devices on the model has been further tested. We have shown that these devices modify very significantly the development of the conical vortex and of its fluctuating pressure footprint.
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Theses
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https://tel.archives-ouvertes.fr/tel-00632367
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Submitted on : Friday, October 14, 2011 - 11:01:07 AM
Last modification on : Wednesday, October 20, 2021 - 3:22:14 AM
Long-term archiving on: : Sunday, January 15, 2012 - 2:21:17 AM

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  • HAL Id : tel-00632367, version 1

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Luis Fernando Gouveia de Moraes. Analyse expérimentale d'un modèle de tourbillon conique et de sa sensibilité à une turbulence amont. Sciences de l'ingénieur [physics]. ISAE-ENSMA Ecole Nationale Supérieure de Mécanique et d'Aérotechique - Poitiers, 2011. Français. ⟨tel-00632367⟩

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