Estimation de paramètres et de conditions limites thermiques en conduction instationnaire pour des matériaux anisotropes. Apport des algorithmes stochastiques à la conception optimale d'expérience.

Abstract : This study deals with the resolution of two types of inverse heat transfer problem : estimation of thermophysical parameters and estimation of thermal boundary conditions. A first part is devoted to the 3D-flash method which is used to estimate the three thermal diffusivities corresponding to the three principal directions of an anisotropic material. This work led to the realization of a experimental setup. The thermal excitation is provided by a CO2 laser and the temperature fields are acquired using infrared thermography. The thermal diffusivities are estimated by combining an estimator, an experiment and an analytical modeling. Different estimators are proposed and compared, based on their standard deviations. Moreover, a procedure to perform experiment design is presented to further reduce these standard deviations. In the second part, two studied cases consisting in estimating thermal boundary conditions are presented. Both underlying systems involve materials whose thermal properties are known. The thermal boundaries are estimated using temperature measurement provided by thermocouples. The first case deals with the evaluation of heat transfer between the gas and the inner-surface of a high pressure hydrogen tank. In the second case, the objective is to estimate the heat flux absorbed by a composite sample exposed to an oxygen-acetylene torch, in order to simulate the ablation phenomena under extreme conditions. Optimization algorithms are essential in this work. Gradient-based methods are used for parameters estimation and thermal boundary estimation problems. Stochastic algorithms appear to be well adapted in the framework of experiment design problems.
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Emmanuel Ruffio. Estimation de paramètres et de conditions limites thermiques en conduction instationnaire pour des matériaux anisotropes. Apport des algorithmes stochastiques à la conception optimale d'expérience.. Autre. ISAE-ENSMA Ecole Nationale Supérieure de Mécanique et d'Aérotechique - Poitiers, 2011. Français. ⟨tel-00664748⟩

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