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Title: Modeling of molecular nitrogen collisions and dissociation processes for direct simulation Monte Carlo

The Direct Simulation Monte Carlo (DSMC) method typically used for simulating hypersonic Earth re-entry flows requires accurate total collision cross sections and reaction probabilities. However, total cross sections are often determined from extrapolations of relatively low-temperature viscosity data, so their reliability is unknown for the high temperatures observed in hypersonic flows. Existing DSMC reaction models accurately reproduce experimental equilibrium reaction rates, but the applicability of these rates to the strong thermal nonequilibrium observed in hypersonic shocks is unknown. For hypersonic flows, these modeling issues are particularly relevant for nitrogen, the dominant species of air. To rectify this deficiency, the Molecular Dynamics/Quasi-Classical Trajectories (MD/QCT) method is used to accurately compute collision and reaction cross sections for the N{sub 2}({sup 1}Σ{sub g}{sup +})-N{sub 2}({sup 1}Σ{sub g}{sup +}) collision pair for conditions expected in hypersonic shocks using a new potential energy surface developed using a ReaxFF fit to recent advanced ab initio calculations. The MD/QCT-computed reaction probabilities were found to exhibit better physical behavior and predict less dissociation than the baseline total collision energy reaction model for strong nonequilibrium conditions expected in a shock. The MD/QCT reaction model compared well with computed equilibrium reaction rates and shock-tube data. In addition, the MD/QCT-computed total crossmore » sections were found to agree well with established variable hard sphere total cross sections.« less
Authors:
;  [1] ;  [2] ;  [3]
  1. Department of Aerospace Engineering, The Pennsylvania State University, 233 Hammond Building, University Park, Pennsylvania 16802 (United States)
  2. Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, 136 Research East, University Park, Pennsylvania 16802 (United States)
  3. Department of Aerospace Engineering, The Pennsylvania State University, 136 Research East, University Park, Pennsylvania 16802 (United States)
Publication Date:
OSTI Identifier:
22413337
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 141; Journal Issue: 23; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; COLLISIONS; DISSOCIATION; EXTRAPOLATION; HYPERSONIC FLOW; MOLECULAR DYNAMICS METHOD; MONTE CARLO METHOD; NITROGEN; REACTION KINETICS; SIMULATION; SURFACES; TOTAL CROSS SECTIONS