Calibration of the Larsen-Borgnakke Model for NO-O Vibrational Relaxation

Abstract Modeling of Nitric Oxide (NO) vibrational states in hypersonic reentry flows is necessary to interpret emission and absorption spectra. To that end, the vibrational relaxation number, $$Z_v^C$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>Z</mml:mi> <mml:mi>v</mml:mi> <mml:mi>C</mml:mi> </mml:msubsup> </mml:math> , is an important parameter in the Larsen-Borgnakke (LB) model which is used to express vibrational relaxation rates for collisions. In this work, we use rates obtained from Quasi-Classical Trajectory (QCT) calculations of Andrienko et al. [2] for the NO-O vibrational relaxation process to arrive at a new fit for the $$Z_v^C$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>Z</mml:mi> <mml:mi>v</mml:mi> <mml:mi>C</mml:mi> </mml:msubsup> </mml:math> parameter. This new fit for $$Z_v^C$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>Z</mml:mi> <mml:mi>v</mml:mi> <mml:mi>C</mml:mi> </mml:msubsup> </mml:math> is implemented in Direct Simulation Monte Carlo (DSMC) calculations for the case of hypersonic flow over a cylinder where the effect of the new fit on NO macroparameters and vibrational state populations is studied.