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Communication Dans Un Congrès Année : 2012

A bypass transition in the Lamb-Oseen vortex

Résumé

Transient energy growth in the short-time linear dynamics of a Lamb-Oseen monopole is a potential mechanism for nonlinear bypass transition, a phenomenon already observed in both experiments and numerical simulations. In the present study, we investigate this scenario by means of a nonlinear optimal perturbation approach, i.e. by looking for the initial perturbation whose evolution satisfies the fully nonlinear Navier-Stokes equations and maximizes the energy gain at a given time horizon. Preliminary two-dimensional results show that, for small initial amplitudes, the optimal perturbation and growth mechanisms observed in the linear regime are recovered. More particularly, the time evolution of the m = 2 optimal perturbation leads to an elliptical core deformation of the monopole, which suggests a potential bypass scenario driven by the non-linear dynamics. This is confirmed by computations for larger initial perturbation amplitudes: the optimal perturbation is similar to that of the linear regime but a subcritical bifurcation to a quasi-steady, high-energy, rotating tripole is observed.
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Dates et versions

hal-04003377 , version 1 (24-02-2023)

Identifiants

  • HAL Id : hal-04003377 , version 1
  • OATAO : 10496

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Luigi Bisanti, Pierre Brancher, Christophe Airiau. A bypass transition in the Lamb-Oseen vortex. 65th Annual Meeting of the American Physical Society's Division of Fluid Dynamics (DFD), Nov 2012, San Diego, United States. pp.0. ⟨hal-04003377⟩
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