Abstract
A new two-temperature model for use in computational fluid dynamics (CFD) simulations for coupled internal energy transfer and dissociation in nitrogen is constructed based on ab-initio data from Direct Molecular Simulation (DMS). The DMS method imbeds trajectory calculations, where molecular collisions are integrated using an ab-initio potential energy surface, within a direct simulation Monte Carlo calculation. As a result, the DMS method is able to directly simulate rovibrational excitation and dissociation processes, including the evolution of non-Boltzmann internal energy distribution functions and coupling to dissociation. Guided by recent DMS results for a full nitrogen system (both N-N2 and N2-N2 collisions), a simple model based on surprisal analysis is found to accurately predict both the overpopulation of high v-level states during rapid excitation and the depletion of high v-level states due to dissociation. Furthermore, both DMS and quasi-classical-trajectory (QCT) results can be used to determine the dissociation probability for molecules in a certain vibrational energy level (v). A simple probability model that is a function of v-level is shown to accurately reproduce DMS data. Combined, the probability expression can be integrated over the surprisal model, which accounts for non-Boltzmann vibrational energy distributions. The result, is a two-temperature (T, Tv) dissociation model that accurately reproduces a range of coupled vibration-dissociation phenomena found in previous studies and in the current DMS results. The new two-temperature model is suitable for large scale CFD simulations.
Original language | English (US) |
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Title of host publication | 46th AIAA Thermophysics Conference |
Publisher | American Institute of Aeronautics and Astronautics Inc, AIAA |
ISBN (Print) | 9781624104350 |
State | Published - 2016 |
Event | 46th AIAA Thermophysics Conference, 2016 - Washington, United States Duration: Jun 13 2016 → Jun 17 2016 |
Other
Other | 46th AIAA Thermophysics Conference, 2016 |
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Country/Territory | United States |
City | Washington |
Period | 6/13/16 → 6/17/16 |