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Title: Modeling of non-equilibrium phenomena in expanding flows by means of a collisional-radiative model

The effects of non-equilibrium in a quasi-one-dimensional nozzle flow are investigated by means of a collisional-radiative model. The gas undergoing the expansion is an air plasma and consists of atoms, molecules, and free electrons. In the present analysis, the electronic excited states of atomic and molecular species are treated as separate pseudo-species. Rotational and vibrational energy modes are assumed to be populated according to Boltzmann distributions. The coupling between radiation and gas dynamics is accounted for, in simplified manner, by using escape factors. The flow governing equations for the steady quasi-one-dimensional flow are written in conservative form and discretized in space by means of a finite volume method. Steady-state solutions are obtained by using a fully implicit time integration scheme. The analysis of the evolution of the electronic distribution functions reveals a substantial over-population of the high-lying excited levels of atoms and molecules in correspondence of the nozzle exit. The influence of optical thickness is also studied. The results clearly demonstrate that the radiative transitions, within the optically thin approximation, drastically reduce the over-population of high-lying electronic levels.
Authors:
;  [1] ;  [2] ;  [3]
  1. Aeronautics and Aerospace Department, von Karman Institute for Fluid Dynamics, Chaussée de Waterloo 72, 1640 Rhode-Saint-Genèse (Belgium)
  2. CORIA, UMR CNRS 6614, Universitè de Rouen, Site universitaire du Madrillet, Avenue de l'Universitè 76801 Saint-Etienne du Rouvray Cedex (France)
  3. Aerospace Department, University of Illinois at Urbana-Champaign, 306 Talbot Lab, 104 S. Wright St., Urbana, Illinois 61801 (United States)
Publication Date:
OSTI Identifier:
22227982
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 20; Journal Issue: 7; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 74 ATOMIC AND MOLECULAR PHYSICS; APPROXIMATIONS; ATOMS; DISTRIBUTION FUNCTIONS; ELECTRONIC STRUCTURE; ELECTRONS; MATHEMATICAL SOLUTIONS; MOLECULES; ONE-DIMENSIONAL CALCULATIONS; PLASMA; PLASMA EXPANSION; ROTATIONAL STATES; STEADY-STATE CONDITIONS; VIBRATIONAL STATES