Novel approach for CO2 state-to-state modeling and application to multi-dimensional entry flows

Amal Sahai, Bruno E. Lopez, Christopher O. Johnston, Marco Panesi

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

This paper presents a physics-based macroscopic model for the description of non- equilibrium effects in CO2 flows. The starting point is the development of a vibrational state-to-state kinetic model including both vibrational excitation and dissociation processes for CO2 internal states. A reduced-order representation is formulated by grouping the vibrational states into a set of macroscopic bins. The novel aspect of this work is to use both the levels’ energy and the magnitude of their transition rates to generate these bins of vibrational states. The state population is then reconstructed from the macroscopic variables using bin-wise distribution functions based on the maximum entropy principle. A reduced system of governing equations is derived by taking successive moments of the fundamental microscopic equations without any ad-hoc assumptions. In order to fulfill the needs of practical multi-dimensional simulations, a set of kinetic and thermodynamic databases are constructed. The accuracy of the grouping strategy is assessed by analyzing the error introduced by the reduced-order models. It is found that the reduced-order state- to-state model can accurately reproduce the internal population and various macroscopic quantities, even for strong non-equilibrium conditions and a reduced number of bins. The reduced-order state-to-state model has been implemented in the US3D code and is applied to the Mars Science Laboratory entry. The conventional Boltzmann and the newly developed state-specific model are compared using a pure CO2 gas mixture. Both approaches shows very similar results in the forebody region of the spacecraft, while large discrepancies are observed in the backshell region, where non-Boltzmann effects become significant.

Original languageEnglish (US)
Title of host publicationAIAA SciTech Forum - 55th AIAA Aerospace Sciences Meeting
PublisherAmerican Institute of Aeronautics and Astronautics Inc.
ISBN (Electronic)9781624104473
DOIs
StatePublished - 2017
Event55th AIAA Aerospace Sciences Meeting - Grapevine, United States
Duration: Jan 9 2017Jan 13 2017

Publication series

NameAIAA SciTech Forum - 55th AIAA Aerospace Sciences Meeting

Other

Other55th AIAA Aerospace Sciences Meeting
CountryUnited States
CityGrapevine
Period1/9/171/13/17

ASJC Scopus subject areas

  • Aerospace Engineering

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