Direct molecular simulation of oxygen dissociation across normal shocks

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We present direct molecular simulations (DMSs) of rovibrational excitation and dissociation of oxygen across normal shock waves. These are the first atomistic simulations of normal shock waves to rely exclusively on ab initio potential energy surfaces to describe the full collision dynamics (accounting for elastic, inelastic and reactive processes) in a dilute gas mixture of molecular and atomic oxygen. The simulated setup aims to reproduce two of the experimental conditions in the shock tube tests of Ibraguimova et al. (J Chem Phys 139:034317, 2013). We compare mixture composition and vibrational temperatures extracted from our simulations with those inferred from the shock tube tests and observe good agreement. In addition to this, we report macroscopic moments due to dissipative transport across the shock, i.e., species diffusion fluxes, viscous stresses and heat flux. Furthermore, we examine the distributions of vibrational and total internal energy of the O 2 molecules at several locations across the shock wave. We are able to follow the gradual transition from pre-shock to post-shock population distributions and, in both cases studied, find depletion of the high-energy tail of the internal energy distributions due to preferential dissociation from states close to the dissociation energy D. Finally, we extract molecular velocity distributions functions (VDF) of O 2 and O at selected locations across the shock to delimit the region where continuum breakdown occurs.

Original languageEnglish (US)
Pages (from-to)41-80
Number of pages40
JournalTheoretical and Computational Fluid Dynamics
Issue number1
StatePublished - Feb 2022
Externally publishedYes

Bibliographical note

Funding Information:
The research is supported by the U.S. Air Force Office of Scientific Research (AFOSR) under Grant FA9550-19-1-0219. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the AFOSR or the U.S. Government.

Publisher Copyright:
© 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.


  • Dissociation in chemical reactions
  • Hypersonic flows
  • Kinetic theory of gases
  • Molecular dynamics calculations in fluid dynamics
  • Shock waves in chemical reaction kinetics


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