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Dynamique des grandes échelles dans les jets turbulents avec ou sans effets de rotation

Abstract : Résumé Traduit : This thesis is a contribution to the study of turbulence in the near field of a jet exit, with or without swirl. We use an experimental setup which has been validated to generate a thin axisymmetric mixing layer developing into a jet, and where the amount of swirl can be precisely set. The flow is characterized using stereoscopic PIV measurements, including high-speed acquisitions which resolve the dynamics of the large scale turbulent structures. We have proposed and tested a method which allows the estimate the convection velocities of these structures and to determine the validity of Taylor's hypothesis using the experimental dataset. This study shows that in the jet near field, it is legitimate to perform a pseudo spatial reconstruction using temporal PIV data. In the jet core, without swirl, a POD confirms the predominance of m=0 and m=1 modes, in line with previous studies. A detailed statistical analysis brings to light that the motion of m=1 modes is closer to a flapping than to a helix. In the mixing layer, streamwise vortices are dominant. Radially oriented pairs are shown to be frequent by analyzing spatial correlation of streamwise vorticity. The relative organization of these vortices with m=0 and m=1 modes is quantitatively established using velocity and vorticity correlations. This leads us to propose an interaction scenario between m=0 and m=1 modes, streamwise vortices, and the mean flow. When swirl is added, the growth rate and turbulent kinetic energy level in the mixing layer do not vary in a monotonous manner. This is due to specific initial conditions obtained from the swirl generation mechanism, which counter the effects arising from the increased alignment between the Reynolds stress and the strain tensor. On this last point, we show that the orientation of the initially radial vortex pair changes with swirl, and this provides a dynamical interpretation of evolution of the Reynolds stress tensor.
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Contributor : Samuel Davoust Connect in order to contact the contributor
Submitted on : Tuesday, March 13, 2012 - 10:32:40 PM
Last modification on : Tuesday, March 16, 2021 - 3:42:04 PM
Long-term archiving on: : Thursday, June 14, 2012 - 6:00:40 PM


  • HAL Id : pastel-00678786, version 1



Samuel Davoust. Dynamique des grandes échelles dans les jets turbulents avec ou sans effets de rotation. Dynamique des Fluides [physics.flu-dyn]. Ecole Polytechnique X, 2011. Français. ⟨pastel-00678786⟩



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