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Home > Seminars and Workshops > Past seminars, PhD & HDR defense > 2017 > Séminaires 2017 > Le jeudi 07 Septembre à 11h

Le jeudi 07 Septembre à 11h

Thierry Magin, Associate Professor au Von Karman Institute
Titre/title : Development of a Lagrangian reactor for detailed chemistry in rarefied flows:
Application to atmospheric entries, Huygens probe and meteors.
Quand/When : Jeudi 07 Septembre 2017, 11 heures
Lieu/Where : salle CPhT / Aile 0, Palaiseau

Résumé :
Understanding thermo-chemical nonequilibrium effects in reactive and plasma flows is important for a variety of aerospace and science applications, ranging from heat shield design for atmospheric entry flows to interpretation of meteor radio observations. Detailed chemistry models are often too computationally expensive to be strongly coupled to flow solvers, in particular in the rarefied flow regime. We have developed a Lagrangian chemical reactor assuming that elementary chemical processes can be decoupled from a steady flow governed by the Maxwell transfer equations. The problem is introduced by studying the electronic energy excitation of the CN molecule in the shock layer of the Huygens probe during its entry into the atmosphere of Titan. Then, the Maxwell transfer equations are derived from kinetic theory, allowing us to take into account rarefied gas effects. The Lagrangian chemical reactor developed follows fluid particles along pre-computed streamlines, integrating the governing equations with boundary conditions picked from the first point of the streamline. Dissipation of energy and mass is assumed decoupled from the detailed chemistry solver, whereas mass diffusion across the stream is considered by means of the Lagrangian reactor. The code developed is applied to simulations of meteors at high altitude using the Direct Simulation Monte Carlo method. Since these simulations are deficient from the chemistry point of view, the Lagrangian reactor can be used to introduce additional processes such as recombination reactions, providing a map of free electrons up to a distance of 2 km from the meteoroid. These simulations tools will be used to interpret radio observation of meteors, and study of platform contamination for electric propulsion thrusters.


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Tutelles : CNRS Ecole Polytechnique Sorbonne Université Université Paris Sud Observatoire de Paris Convention : CEA
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