Modelisation of aero-optic effects in supersonic conditions
Lafontaine, Pierre
Promotor(s) :
Terrapon, Vincent
Date of defense : 25-Jun-2018/26-Jun-2018 • Permalink : http://hdl.handle.net/2268.2/4545
Details
Title : | Modelisation of aero-optic effects in supersonic conditions |
Translated title : | [fr] Modélisation des effets aéro-optiques d'un écoulement supersonique |
Author : | Lafontaine, Pierre ![]() |
Date of defense : | 25-Jun-2018/26-Jun-2018 |
Advisor(s) : | Terrapon, Vincent ![]() |
Committee's member(s) : | Vassen, Jean-Marc
Loicq, Jerôme ![]() |
Language : | English |
Keywords : | [fr] Aerodynamics Optics |
Discipline(s) : | Engineering, computing & technology > Aerospace & aeronautics engineering |
Institution(s) : | Université de Liège, Liège, Belgique |
Degree: | Master en ingénieur civil en aérospatiale, à finalité spécialisée en "aerospace engineering" |
Faculty: | Master thesis of the Faculté des Sciences appliquées |
Abstract
[fr] Optical distortions are observed everywhere, in nature and in man-crafted technologies. These distortions affect the performances of the optical systems, and as such present an interest to be studied.
In the context of an airborne optical device, the optical perturbations are mostly due to the near-field perturbation of the flow. Considering a supersonic flow, the perturbed region is limited by a shock wave. The perturbed region which generates the optical aberrations is therefore clearly defined. A missile optical guidance system is chosen as a model for the simulations.
Acknowledging the importance of aerodynamic heating through shocks and heat exchanges in the boundary layer, a fluid-structure interaction simulation is performed. The density field of the flow can be directly related to the index of refraction; the increase of temperature of the optical window induce a modification of the index of refraction. Finally thermo-elastic deformations occurs due to the increase of temperature.
The surface of the shock wave is fitted by a polynomial surface: it is expected to provide a good characterization of the optical effect of the shock.
The optical performances of the system under aero-optic disturbances are computed by ray tracing.
The results are consistent with the expected optical effects of the aberrations, and show that the heating of the optical window dominates the deterioration of the optical performances. For an hemispherical window in a flow of Mach 4 and an angle of view of 20 degree, the boresight shift is equal to 0.57 [mrad].
The sucessfull computation of aberrations in the same order of magnitude as reference simulations supports the importance of the characterization of the shock surface.
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