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Theses

Etude numérique des effets de température dans les jets simples et coaxiaux

Abstract : This thesis investigates temperature eects on subsonic turbulent single-stream and dual-stream jets and their far-field acoustic signature. The full compressible Navier-Stokes equations are solved using Large-Eddy Simulation, and open Kirchho's surface integral method is used to extend the acoustic prediction to far-field location. In order to study sound source mechanisms of isothermal and heated jets, at the same Mach and Reynolds numbers, Lighthill's tensor source terms are decomposed in Fourier modes in the azimuthal direction. The main features in the modal structure of a heated jet are the entropy term contribution and the importance of the relative energy contained in higher order modes. We show that the entropy term and the linear density fluctuation term have a similar behaviour in the near-field, for both the spatial distribution of the energy and the frequency dependence. For the dual-stream jets, heating the primary jet leads to a vortex pairing between the inner and outer shear layers. Sound radiated in the downstream direction is shown to depend appreciably on this phenomenon. Finally, we proposed some model problems to test the performance and utility, in terms of the physical insight which is provided, of an energy corollary, based on Helmholtz decompositions of both linear momentum and velocity. We show it is possible to identify the dierent flow processes (source mechanisms) which lead to the transport of fluctuation energy, as well as the physical mechanisms by which that fluctuation energy is transported away from the source region as propagating sound energy.
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https://tel.archives-ouvertes.fr/tel-00573368
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Submitted on : Thursday, March 3, 2011 - 3:18:06 PM
Last modification on : Wednesday, October 20, 2021 - 3:22:14 AM
Long-term archiving on: : Saturday, December 3, 2016 - 12:15:56 PM

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  • HAL Id : tel-00573368, version 1

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Guillaume Daviller. Etude numérique des effets de température dans les jets simples et coaxiaux. Sciences de l'ingénieur [physics]. ISAE-ENSMA Ecole Nationale Supérieure de Mécanique et d'Aérotechique - Poitiers, 2010. Français. ⟨tel-00573368⟩

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