LINE BY LINE AND STATISTICAL NARROW-BAND CALCULATIONS OF RADIATIVE TRANSFER IN SOME ATMOSPHERIC ENTRY PROBLEMS

摘要

The aim of this paper is to contribute to the benchmarking of radiative properties and radiative transfer in high temperature gases through test cases 1 and 3. A line by line (LBL) approach, based on exhaustive spectroscopic data that were previously developed in our laboratory, is used for both cases. For test case 1, a good global agreement is found between our calculations and the emission spectra measured by Laux (1993) from an ICP air plasma torch, producing LTE air plasma at temperatures up to 7600 K. Detailed comparisons show however some differences in the background level and, sometimes, in the absolute intensity and spectral position of the emitted signal. Most of these discrepancies are attributed to experimental calibrations that were corrected in more recent experiments (Laux 2002). Our contribution for test case 3 consists in computing radiative transfer in the wake of an axially symmetric body entering Martian atmosphere. Temperature and concentration fields are prescribed entries. We use line by line calculations with a ray-tracing method to provide reference solutions and develop a statistical narrow-band (SNB) model suitable for high temperature-low pressure applications. The analysis of radiative transfer in this application shows that the medium cannot be considered as optically thin and that the application of the weak absorption limit of SNB models, or equivalently, a smeared rotational model, leads to important discrepancies. The accuracy and numerical efficiency of the SNB model are emphasised.