Effect of free-stream turbulence on conical vortex dynamics
Résumé
The influence of Free-Stream Turbulence (FST) on the space–time dynamics of a conical vortex developing alonga A-pillar is studied experimentally. Measurements of unsteady wall pressure and velocity by High Speed-StereoPIV highlight the important effects of turbulence on the mean and instantaneous properties of the vortex. Verysignificant increases in Reynolds stresses into the vortex region and in wall fluctuating pressure are observed inthe presence of FST. In smooth flow, the frequency content of the pressure and velocity fields is very rich withlow and high frequency contributions due to the meandering of the vortex and instabilities in the vortex core.Meandering shows, for the different integral length scales and intensities of turbulence tested, a great receptivityto the presence of a FST and we observe a global motion of the vortex structure at low frequency. This frequencyis modulated by the value of the integral length scale of the FST. We show that the mean conical structure is awave guide for the perturbations of the core but that, with FST, the spatio-temporal evolution of the envelopeoverwhelms the intrinsic instability of the vortex core observed in smooth flow
Domaines
Mécanique [physics.med-ph]Origine | Fichiers produits par l'(les) auteur(s) |
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