Numerical Analysis on the Nonequilibrium Phenomena of the Electronic Excitation Process behind Hypersonic Shock Waves

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In this study, the nonequilibrium phenomena of the electronic excitation process behind hypersonic shock waves have been investigated through numerical analysis. In the analysis, the three-temperature model is employed and temperature profiles are computed along the distance from the shock front. In the three-temperature model, the translational–rotational, vibrational and electron-electronic excitation temperatures are separately described and the relaxation processes for each energy mode are considered. Numerical calculations are conducted under the conditions corresponding to the shock tube experiments conducted in our previous study and the results are compared with the experimental data. It is found that the calculated and measured vibrational temperature profiles are in good agreement. In contrast, the calculated electronic excitation temperature is much lower than the measured one, revealing the discrepancy in the modeling of the electronic excitation temperature. To investigate the effect of electron behavior, parametric studies are conducted using the three-temperature model. The calculated temperatures agree well with the measured temperatures by considering the electrons in the region ahead of the shock wave. This result suggests that the effect of electron behavior is significant for hypersonic shock waves and a detailed model to describe the nonequilibrium phenomena is needed.