Investigating the radiation characteristics of high-temperature flow fields around near-space vehicles holds critical significance, with key applications in aerothermal environment prediction, optical radiation noise estimation and related fields. This study employs the thermochemical nonequilibrium Navier-Stokes equations and the radiation transfer equation, taking the RAM-C blunt cone as the study object to analyze the radiation characteristics at different surface positions (including the stagnation point, windward/leeward meridians, and base center) under high-altitude and high-speed flight conditions. The results indicate that, under high-altitude and high-speed conditions, the flow fields in the compression zone ahead of the blunt cone and its wake region are both in a non-equilibrium state, with significant differences in radiation characteristics across different surface positions. At blunt cone apex, the dissociation of air components generates significant amounts of N atoms, O atoms and NO molecules, with the total irradiance predominantly composed of atomic radiation mechanisms and NO molecular radiation mechanisms, accounting for 22.14% and 73.98%, respectively. At other locations on the blunt cone surface, the degree of air dissociation is significantly reduced, with the atomic radiation mechanism contributing less than 5% to the total irradiance, while over 90% of the irradiance originates from NO molecules. The radiation intensity at the base center of blunt cone is significantly lower than other positions, being three orders of magnitude weaker compared to the apex. Additionally, the radiance is strongly dependent on the viewing aspect (defined by polar and azimuthal angles) and spectral band. The calculation results show that the lowest radiance at the base center occurs along the direction 45° polar angle and 90° azimuthal angle within the 600~700 nm spectral band.
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