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Absolute/convective instabilities in the Batchelor vortex: A numerical study of the linear impulse response. (English) Zbl 0905.76030
The absolute/convective instability properties of the Batchelor vortex are determined by direct numerical simulation of the linear impulse response. A decomposition procedure is applied to the computed wavepacket in order to retrieve the complex wavenumber and frequency prevailing along each spatio-temporal ray. In particular, the absolute wavenumber and frequency observed in the laboratory frame are determined as a function of swirl parameter and external flow. The introduction of a moderate amount of swirl is found to strongly promote absolute instability.

MSC:
76E15 Absolute and convective instability and stability in hydrodynamic stability
76M25 Other numerical methods (fluid mechanics) (MSC2010)
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