In this work we present a molecular level study of N2+N collisions, focusing on excitation of internal energy modes and non-equilibrium dissociation. The computation technique used here is the direct molecular simulation (DMS) method and the molecular interactions have been modeled using an ab−initio potential energy surface (PES) developed at NASA’s Ames Research Center. We carried out vibrational excitation calculations between 5000K and 30000K and found that the characteristic vibrational excitation time for the N + N2process was an order of magnitude lower than that predicted by the Millikan and White correlation. It is observed that during vibrational excitation the high energy tail of the vibrational energy distribution gets over populated first and the lower energy levels get populated as the system evolves. It is found that the non-equilibrium dissociation rate coefficients for the N + N2process are larger than those for the N2+ N2process. This is attributed to the non-equilibrium vibrational energy distributions for the N + N2process being less depleted than that for the N2+ N2process. For an isothermal simulation we find that the probability of dissociation goes as 1/Ttrfor molecules with internal energy (∈int) less than ∼ 9.9eV,while for molecules with ∈int>9.9eV the dissociation probability was weakly dependent on translational temperature of the system. We compared non-equilibrium dissociation rate coefficients and characteristic vibrational excitation times obtained by using the ab − initio PES developed at NASA’s Ames Research Center to those obtained by using an ab − initio PES developed at the University of Minnesota. Good agreement was found between the macroscopic properties and molecular level description of the system obtained by using the two PESs.
|Original language||English (US)|
|Title of host publication||AIAA SciTech Forum - 55th AIAA Aerospace Sciences Meeting|
|Publisher||American Institute of Aeronautics and Astronautics Inc.|
|State||Published - 2017|
|Event||55th AIAA Aerospace Sciences Meeting - Grapevine, United States|
Duration: Jan 9 2017 → Jan 13 2017
|Name||AIAA SciTech Forum - 55th AIAA Aerospace Sciences Meeting|
|Other||55th AIAA Aerospace Sciences Meeting|
|Period||1/9/17 → 1/13/17|
Bibliographical noteFunding Information:
The research presented is supported by Air Force Office of Scientific Research (AFOSR) under Grant No. 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 authors would like to thank Dr. Michael Barnhardt and Dr. David Hash at NASA?s Ames Research Center for providing the opportunity for collaboration between Ames Research Center and the University of Minnesota. Maninder Grover was supported by the Doctoral Dissertation Fellowship at the University of Minnesota.
© 2017 by Maninder S. Grover, Thomas E. Schwartzentruber and Richard L. Jaffe.