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Vers des simulations numériques prédictives des détonations gazeuses : influence de la cinétique chimique, de l’equation d’etat et des effets tridimensionnels

Abstract : This study is part of the general framework of numerical simulations of detonations under non-ideal conditions.The configurations discussed correspond to flows encountered in industrial hazards and rotating detonation engines.Simulations are based on an inhouse code RESIDENT (REcycling mesh SImulation of DEtonations) developed at the Pprime Institute. It is based on high-order shock capturing schemes, with a MP9 interpolation scheme, a HLLC-M solver and a 3rd Runge-Kutta time integration. At first, the influence of the equation of state (EOS) on the cellular detonation structure has been studied with two EOS : Perfect gas and Noble-Abel. The numerical results have shown that new triples points are generated from the interaction of a slip line with already existing triple points. The increase of the post-shock isentropic coeffient has inhibited the appearance of these instabilities and has regularized the cell structure. This results may be important as engineering correlations are based on the cell size and regularity. Secondly, the influence of chemical modelling on the structure of the detonation and its extinction limits were studied using three kinetic models of increasing complexity : single-step, three-step chain-branching and detailed chemistry. Despite the macroscopic features are similar, the outcome of the critical height of a detonation confined by an inert layer is significantly different, highlighting the impact of the kinetics in predicting the extinction limits observed in experiments. Finally, the influence of three-dimensional effects on the dynamics of detonation was studied. Comparisons of 2-D and 3-D simulations are carried out in the case of marginal and semi-confined detonations. Despite the differences observed in the flow topology, similarities were found in the mean structure when the detonation propagation is ideal. The analysis of the total fluctuation energy revealed that entropy fluctuations are more important than pressure fluctuations. In the case of semi-confined detonation, 3-D effects manifests a smaller velocity deficit than in 2-D when the detonation propagates at the same reactive height. The velocity deficitis correlated to the ratio of the hydrodynamic thickness to the radius of curvature, despite the higher average curvature of the 3-D front.
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Submitted on : Thursday, December 17, 2020 - 9:40:28 AM
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Saïd Taileb. Vers des simulations numériques prédictives des détonations gazeuses : influence de la cinétique chimique, de l’equation d’etat et des effets tridimensionnels. Autre. ISAE-ENSMA Ecole Nationale Supérieure de Mécanique et d'Aérotechique - Poitiers, 2020. Français. ⟨NNT : 2020ESMA0012⟩. ⟨tel-03079083⟩

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