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Accueil > Evénements Scientifiques > Conférences et Séminaires > Conférences et séminaires 2012 > Luigi Bisanti - 23 janvier à 14H00, salle Castex

Luigi Bisanti - 23 janvier à 14H00, salle Castex

26 janvier 2012

Generalized stability analysis of shielded vortices

Luigi Bisanti, doctorant EMT2

Lundi 23 janvier, 14H00, salle Castex

séminaire EMT2, ouvert à tous

Abstract :

The generalized stability analysis of a family of isolated vortices characterized by a non-monotonic vorticity profile is performed for low Reynolds numbers. The modal temporal stability analysis allows the neutral curve to be computed. Then, for the particular case of the Taylor vortex, a subcritical optimal perturbation analysis proves that transient energy growths can occur for various azimuthal wavenumbers and a study in the supercritical case completes the short-time analysis. The physical analysis of the optimal disturbances reveals some typical mechanisms of growth observed in the Lamb-Oseen vortex, leading to a generalization of the optimal amplification processes involving vortices. Lastly the effects of a diffusive base flow are investigated, the results proving that the base flow diffusion simply plays a trivial spatial lenght rescaling without introduce any new mechanism. The short-time analysis by means of the optimal perturbation tool will complete the long-time analysis, showing that the most unstable mode found by the classical stability analysis is not necessarily the most dangerous at short period.