Evaluation of an approximate narrow-band formulation for non-grey radiative transfer calculation in three-dimensional absorbing-emitting-scattering media

摘要

A grey-band approximation was developed for modelling the low-resolution spectralradiance or the infrared signature from a rocket exhaust plume containing an absorbing-emitting-scattering mixture.The mean gas absorption coefficient of a narrow-band was estimated using the gas transmissivifty based on the mean path-length using the gas transmissivity based on the mean path-length of the local ocmputational grod soze/Radoative properties of particulate were calculated using Mie theory.Accuracy of the approximate formulation was evaluated in an isothermal and homogeneous plume of 1800 K for a narrow-band of 25 cm~-1 wide by comparing the approxmiate results with 'line-by-line' results generated using an artificial gas spectral absoption coefficient.The artificial gas absorption coefficient was varied by two orders of magnitude to simulate strong and weak absorption bands. The grey-band model overpredicts the wavenumber integrated radiation intensity in the narrow-band by as much as 13