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Proceedings Paper

Numerical study of the wavefront distortion in an aerodynamical flow field
Author(s): B. Sorrente; P. d'Espiney; R. Deron
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Paper Abstract

Optical aberrations induced by turbulent flows are critical issues for the performance of an airborne optical system. In that context experiments were performed on a test-body at Mach 3.7 with several high Reynolds number in the S3MA wind tunnel of ONERA. A Shack-Hartman wave front sensing was performed (see companion paper of R. Deron). The objective of this work was to develop a computational algorithm to model the wave front distortions in temporal averaged field. First the aerodynamical flow field is obtained by RANS computation around the test body and mass-density is interpolated in an optical grid. Then wave front has been calculated using ray tracing from eikonal equations. For this validation two Reynolds numbers were retained and the boundary layer is turbulent on downstream window. A planar optical beam is emitted from the window and passes through the inhomogeneous media from the boundary layer to the shock wave. Various pupil, angle positions and lines of sight are considered. Zernike decomposition and MTF computation allow modal analysis in the near field condition and evaluation of the image quality respectively. Tilt effects appear to be the dominant aberration while higher orders have a limited impact on the image quality, except for large departures from the normal of the window. Discrepancies observed according to the line of sight variation are analysed. Finally simulations results compare favorably with the measurements made with the Shack-Hartmann wave front sensing. So this computational study is conforted and allows to complete the experiment.

Paper Details

Date Published: 9 October 2008
PDF: 10 pages
Proc. SPIE 7108, Optics in Atmospheric Propagation and Adaptive Systems XI, 71080C (9 October 2008); doi: 10.1117/12.802773
Show Author Affiliations
B. Sorrente, ONERA (France)
P. d'Espiney, ONERA (France)
R. Deron, ONERA (France)

Published in SPIE Proceedings Vol. 7108:
Optics in Atmospheric Propagation and Adaptive Systems XI
Anton Kohnle; Karin Stein; John D. Gonglewski, Editor(s)

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