Modeling of nonequilibrium radiation phenomena - An assessment

The present understanding of shock-layer radiation in the low-density regime, as appropriate to hypersonic vehicles, is discussed. Calculated spectra using the NONEQ and GENRAD computer programs are compared with experimental spectra recorded at NASA Ames's electric arc-driven shock-tube facility. The computations predict the intensity of the Nj(1~) system very well, but overpredict the intensities of various atomic O and N transitions and underpredict the intensities of the N2(2) band system. To compute the correct electronic populations, it appears that the quasi-steady-state formulation must be expanded to include more individual electronic states. However, this may cause some computational difficulties and will require excitation rate data for many states, which are not well known.

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