Nonequilibrium Zeldovich-von Neumann-Doring theory and reactive flow modeling of detonation |
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Authors: | C M Tarver J W Forbes P A Urtiew |
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Institution: | (1) Lawrence Livermore National Laboratory, P.O. Box 808, L-282, Livermore, CA 94551, USA |
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Abstract: | This paper discusses the Nonequilibrium Zeldovich-von Neumann-Doring (NEZND) theory of self-sustaining detonation waves and
the Ignition and Growth reactive flow model of shock initiation and detonation wave propagation in solid explosives. The NEZND
theory identified the nonequilibrium excitation processes that precede and follow the exothermic decomposition of a large
high explosive molecule into several small reaction product molecules. The thermal energy deposited by the leading shock wave
must be distributed to the vibrational modes of the explosive molecule before chemical reactions can occur. The induction
time for the onset of the initial endothermic reactions can be calculated using high pressure-high temperature transition
state theory. Since the chemical energy is released well behind the leading shock front of a detonation wave, a physical mechanism
is required for this chemical energy to reinforce the leading shock front and maintain its overall constant velocity. This
mechanism is the amplification of pressure wavelets in the reaction zone by the process of de-excitation of the initially
highly vibrationally excited reaction product molecules. This process leads to the development of the three-dimensional structure
of detonation waves observed for all explosives. For practical predictions of shock initiation and detonation in hydrodynamic
codes, phenomenological reactive flow models have been developed. The Ignition and Growth reactive flow model of shock initiation
and detonation in solid explosives has been very successful in describing the overall flow measured by embedded gauges and
laser interferometry. This reactive flow model uses pressure and compression dependent reaction rates, because time-resolved
experimental temperature data is not yet available. Since all chemical reaction rates are ultimately controlled by temperature,
the next generation of reactive flow models will use temperature dependent reaction rates. Progress on a statistical hot spot
ignition and growth reactive flow model with multistep Arrhenius chemical reaction pathways is discussed.
The text was submitted by the authors in English. |
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