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Title: A study of internal energy relaxation in shocks using molecular dynamics based models

Recent potential energy surfaces (PESs) for the N{sub 2} + N and N{sub 2} + N{sub 2} systems are used in molecular dynamics (MD) to simulate rates of vibrational and rotational relaxations for conditions that occur in hypersonic flows. For both chemical systems, it is found that the rotational relaxation number increases with the translational temperature and decreases as the rotational temperature approaches the translational temperature. The vibrational relaxation number is observed to decrease with translational temperature and approaches the rotational relaxation number in the high temperature region. The rotational and vibrational relaxation numbers are generally larger in the N{sub 2} + N{sub 2} system. MD-quasi-classical trajectory (QCT) with the PESs is also used to calculate the V-T transition cross sections, the collision cross section, and the dissociation cross section for each collision pair. Direct simulation Monte Carlo (DSMC) results for hypersonic flow over a blunt body with the total collision cross section from MD/QCT simulations, Larsen-Borgnakke with new relaxation numbers, and the N{sub 2} dissociation rate from MD/QCT show a profile with a decreased translational temperature and a rotational temperature close to vibrational temperature. The results demonstrate that many of the physical models employed in DSMC should be revisedmore » as fundamental potential energy surfaces suitable for high temperature conditions become available.« less
Authors:
;  [1] ;  [2]
  1. Department of Aerospace Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)
  2. Department of Aerospace Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois 61801-2935 (United States)
Publication Date:
OSTI Identifier:
22489712
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 143; Journal Issue: 14; Other Information: (c) 2015 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; CROSS SECTIONS; DISSOCIATION; HYPERSONIC FLOW; MOLECULAR DYNAMICS METHOD; MONTE CARLO METHOD; POTENTIAL ENERGY; RELAXATION; SIMULATION; SURFACES