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Dynamique et stabilité de tourbillons avec écoulement axial

Abstract : This fundamental study presents experimental and numerical results concerning the dynamics and stability of vortices with axial core flow, for moderate Reynolds numbers. The first part of the thesis focuses on the elliptic instability in co- and counter-rotating vortex pairs with axial core flow. The stability analysis of two Batchelor vortices clearly identifies elliptic instability modes with complex spatial structures, for a range of axial flows and axial wave numbers. Experimentally, the elliptic instability was evidenced in co- and counter-rotating vortices, generated by two half wings in a water channel. High-speed video recordings and Proper Orthogonal Decomposition of dye visualizations allowed a precise characterization of the instability mode, which involves perturbations of azimuthal wave numbers m=0 and m=2, fulfilling the elliptic instability resonance condition. The numerical stability analysis of the experimental vortices revealed the same unstable mode. Experimental and numerical wavelengths and growth rates are in good agreement. The second part of the thesis deals with "vortex meandering", studied experimentally by generating a single wing-tip vortex. A detailed analysis of the vortex perturbations successfully links this phenomenon to the theory of transient growth of an isolated vortex.
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Submitted on : Friday, November 27, 2009 - 5:53:31 PM
Last modification on : Thursday, January 23, 2020 - 6:22:06 PM
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  • HAL Id : tel-00436894, version 1

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Clément Roy. Dynamique et stabilité de tourbillons avec écoulement axial. Dynamique des Fluides [physics.flu-dyn]. Université de Provence - Aix-Marseille I, 2008. Français. ⟨tel-00436894⟩

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