Modeling of dissociation and energy transfer in shock-heated nitrogen flows

This work addresses the modeling of dissociation and energy transfer processes in shock heated nitrogen flows by means of the maximum entropy linear model and a newly proposed hybrid bin vibrational collisional model. Both models aim at overcoming two of the main limitations of the state of the art...

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Bibliographic Details
Published in:Physics of fluids (1994) 2015-12, Vol.27 (12)
Main Authors: Munafò, A., Liu, Y., Panesi, M.
Format: Article
Language:English
Subjects:
Bins
Boltzmann distribution
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
DISSOCIATION
DISTRIBUTION
Energy levels
Energy of dissociation
ENERGY TRANSFER
ENTROPY
EQUATIONS
Fluid dynamics
Mathematical models
Maximum entropy
Model accuracy
Modelling
MOLECULES
NITROGEN
Physics
Predictions
SIMULATION
VIBRATIONAL STATES
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Summary:This work addresses the modeling of dissociation and energy transfer processes in shock heated nitrogen flows by means of the maximum entropy linear model and a newly proposed hybrid bin vibrational collisional model. Both models aim at overcoming two of the main limitations of the state of the art non-equilibrium models: (i) the assumption of equilibrium between rotational and translational energy modes of the molecules and (ii) the reliance on the quasi-steady-state distribution for the description of the population of the internal levels. The formulation of the coarse-grained models is based on grouping the energy levels into bins, where the population is assumed to follow a Maxwell-Boltzmann distribution at its own temperature. Different grouping strategies are investigated. Following the maximum entropy principle, the governing equations are obtained by taking the zeroth and first-order moments of the rovibrational master equations. The accuracy of the proposed models is tested against the rovibrational master equation solution for both flow quantities and population distributions. Calculations performed for free-stream velocities ranging from 5 km/s to 10 km/s demonstrate that dissociation can be accurately predicted by using only 2-3 bins. It is also shown that a multi-temperature approach leads to an under-prediction of dissociation, due to the inability of the former to account for the faster excitation of high-lying vibrational states.
ISSN:1070-6631
1089-7666
DOI:10.1063/1.4935929