Dissociation is strongly coupled to the vibrational energy population of the dissociating gas. High-temperature excitation results in the overpopulation of high-energy states which enhances the dissociation rate as high-vibrational energy states are strongly favored to dissociation. Dissociation then results in the depletion of the high-energy population and consequently a balance between excitation and dissociation is reached resulting in quasi-steady state (QSS). QSS is characterized by time invariant non-Boltzmann depleted distributions and therefore reduced dissociation rates relative to the equilibrium estimates. In the kinetics models developed thus far, either the non-Boltzmann effects are ignored or added as pre-factors in an ad-hoc manner to an equilibrium rate constant. Recently, using ab initio potential energy surfaces, direct molecular simulation (DMS) approach has simulated the evolution of air species at the conditions representative of post-shock conditions. Based on the DMS data, a simple physics based model to characterize the non-Boltzmann distributions is developed. The model is compared with zero dimensional DMS simulations for nitrogen and oxygen at constant temperature (isothermal) and constant energy (adiabatic) conditions. The non-Boltzmann distributions are then used in conjunction with state-specific dissociation rate constants to derive a non-equilibrium continuum dissociation model.
|Original language||English (US)|
|Title of host publication||AIAA Scitech 2020 Forum|
|Publisher||American Institute of Aeronautics and Astronautics Inc, AIAA|
|State||Published - 2020|
|Event||AIAA Scitech Forum, 2020 - Orlando, United States|
Duration: Jan 6 2020 → Jan 10 2020
|Name||AIAA Scitech 2020 Forum|
|Conference||AIAA Scitech Forum, 2020|
|Period||1/6/20 → 1/10/20|
Bibliographical noteFunding Information:
The research presented is supported by Air Force Office of Scientific Research Grant FA9550-16-1-0161. 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 US government. The research is also partially supported by Doctoral Dissertation Fellowship at the University of Minnesota.
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