A numerical simulation study was performed to examine the post-detonation reaction processes produced by the detonation of a 12 mm diameter hemispherical pentaerythritol tetranitrate (PETN) explosive charge. The simulations used a finite rate detailed chemical reaction model consisting of 59 species and 368 reactions to capture post-detonation reaction processes including air dissociation from Mach 19+ shock waves that initially break out of the PETN charge, reactions within the detonation products during expansion, and afterburning when the detonation products mix with the shock heated air. The multi-species and thermodynamically complete Becker–Kistiakowsky–Wilson real-gas equation of state is used for the gaseous phase to allow for the mixing of reactive species. A recent simplified reactive burn model is used to propagate the detonation through the charge and allow for detailed post-detonation reaction processes. The computed blast, shock structures, and mole fractions of species within the detonation products agree well with experimental measurements. A comparison of the simulation results to equilibrium calculations indicates that the assumption of a local equilibrium is fairly accurate until the detonation products rapidly cool to temperatures in the range of 1500–1900 K by expansion waves. Below this range, the computed results show mole fractions that are nearly chemically frozen within the detonation products for a significant portion of expansion. These results are consistent with the freeze out approximation used in the blast modeling community.
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Post-detonation fireball modeling: Validation of freeze out approximations
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June 2023
Research Article|
June 07 2023
Post-detonation fireball modeling: Validation of freeze out approximations

Special Collection:
Shock Waves
Anthony A. Egeln, Jr.
;
Anthony A. Egeln, Jr.
(Data curation, Formal analysis, Investigation, Methodology, Visualization, Writing – original draft, Writing – review & editing)
1
Department of Mechanical and Aerospace Engineering, University of Florida
, Gainesville, Florida 32611, USA
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John C. Hewson
;
John C. Hewson
(Conceptualization, Supervision, Validation)
2
Sandia National Laboratories
, Alburquerque, New Mexico 87185, USA
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Daniel R. Guildenbecher
;
Daniel R. Guildenbecher
(Conceptualization, Funding acquisition, Investigation, Project administration, Resources, Supervision, Validation, Writing – review & editing)
2
Sandia National Laboratories
, Alburquerque, New Mexico 87185, USA
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Ryan T. Marinis;
Ryan T. Marinis
(Data curation, Validation)
2
Sandia National Laboratories
, Alburquerque, New Mexico 87185, USA
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Marc C. Welliver;
Marc C. Welliver
(Funding acquisition, Project administration, Resources, Supervision)
2
Sandia National Laboratories
, Alburquerque, New Mexico 87185, USA
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Ryan W. Houim
Ryan W. Houim
a)
(Conceptualization, Formal analysis, Funding acquisition, Methodology, Resources, Software, Supervision, Validation, Writing – original draft, Writing – review & editing)
1
Department of Mechanical and Aerospace Engineering, University of Florida
, Gainesville, Florida 32611, USA
a)Author to whom correspondence should be addressed: rhouim@ufl.edu
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a)Author to whom correspondence should be addressed: rhouim@ufl.edu
Note: This paper is part of the special topic, Shock Waves.
Physics of Fluids 35, 066117 (2023)
Article history
Received:
April 06 2023
Accepted:
May 21 2023
Connected Content
A companion article has been published:
Explosive behavoir: Characterizing the freeze-out assumption in post-detonation explosive reactions
Citation
Anthony A. Egeln, John C. Hewson, Daniel R. Guildenbecher, Ryan T. Marinis, Marc C. Welliver, Ryan W. Houim; Post-detonation fireball modeling: Validation of freeze out approximations. Physics of Fluids 1 June 2023; 35 (6): 066117. https://doi.org/10.1063/5.0153334
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