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Caractérisation des écoulements instationnaires 3D par tomographie holographique numérique multidirectionnelle

Abstract : This PhD work is part of the metrological development of optical methods applied to Fluid Mechanics to characterize 2D and 3D complex aerodynamic phenomenon. One of these techniques is digital holography which measures flow phase, directly linked to the refractive index integration. Gas density is deduced thanks to Gladstone-Dale relationship. If phase measurements are done along several viewpoints, gas density can be rebuilt in 3D by tomography. Firstly, digital holography was developed to measure high density gradients encountered in compressible wind tunnels. Then, three campaigns were made on steady 3D flows to compare performances of digital holography to differential interferometry and Background Oriented Schlieren (BOS) which measure light deviation, integration of the derivative of refractive index. 3D reconstruction algorithm developed by Onera/DMPE for 3DBOS, based on conjugated gradients method of a least squared regularized by Tikhonov minimization criterion, was adapted to phase measurements. Reconstructions with 36 different viewpoints were compared to reconstructions obtained by differential interferometry and BOS. Finally, the analysis of the viewpoint number needed to reconstruction showed its dependency with 3D complexity of the jet, what led to the implementation a digital holographic set-up with six simultaneous viewpoints to rebuild with success unsteady flows.
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Submitted on : Friday, October 19, 2018 - 4:36:13 PM
Last modification on : Monday, December 13, 2021 - 9:16:46 AM
Long-term archiving on: : Sunday, January 20, 2019 - 3:40:31 PM

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  • HAL Id : tel-01899629, version 1

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François Olchewsky. Caractérisation des écoulements instationnaires 3D par tomographie holographique numérique multidirectionnelle. Mécanique des fluides [physics.class-ph]. Université Lille 1, 2017. Français. ⟨NNT : ⟩. ⟨tel-01899629⟩

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