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Rayonnement des ondes d'instabilités dans les jets supersoniques

Abstract : The basic purpose of the present thesis is to examine the phenomenon of
acoustic radiation of supersonic jet flows by resorting to the linear
instability theory.
Thus, the downstream development of vortical structures is represented as
a collection of spatially growing instability waves of various frequencies.
At the local level description, it is shown that a simple topological
relationship between roots of the dispersion relation and branch cuts
determines two generic configurations for the time-asymptotic Green's function,
depending on control parameters.
Both configurations leads to the conclusion that a local analysis is not
appropriate to describe the sound emission.
In some cases, the cross-stream behaviour of pressure fluctuations
becomes dispersive and the cross-stream decay of the amplitude changes
from exponential to algebraic.
Such a transition arises in regions of physical space where noise is
generated and depends to a large extent on the jet Mach number.
In this thesis, it is shown how algebraic decays are completely
compatible with the features of the near-field, in terms of a
turning-point problem, and finally, a selection criterion for the occurence
of such a behaviour is given.
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Contributor : Christophe Millet <>
Submitted on : Tuesday, September 2, 2003 - 2:34:20 PM
Last modification on : Friday, June 26, 2020 - 2:02:05 PM
Long-term archiving on: : Wednesday, September 12, 2012 - 10:20:09 AM


  • HAL Id : tel-00003293, version 1



Christophe Millet. Rayonnement des ondes d'instabilités dans les jets supersoniques. Dynamique des Fluides [physics.flu-dyn]. Ecole nationale superieure de l'aeronautique et de l'espace, 2003. Français. ⟨tel-00003293⟩



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