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Bound-state characteristic temperature method and its applications

As the speed of a hypersonic vehicle increases, atomic emission lines in the shock-layer would be the main source of radiative heating. Therefore, it is very important to study the atomic excitation in the air plasma in the shock-layer. For thermal nonequilibrium air plasmas, the equilibrium state statistical theory is not applicable. Although full models (such as the collisional-radiative model) can be used to solve nonequilibrium problems with high accuracy, they are too computationally expensive and difficult to apply in engineering. In this work, we investigate the atomic excitation in air plasmas by means of a bound-state characteristic temperature (BCT) method. Some cases of equilibrium and nonequilibrium air plasmas associated with the well-known FIRE II flight experiment are considered. The calculated atomic energy level populations are in good agreement with the CR model. It shows that our calculation is reason-able and have a good accuracy. The computational efficiency is more than 2000 times higher than the CR model. If used in the flowfield of a hypersonic vehicle, the computational cost can be greatly reduced.