ON THE COMPROMISE BETWEEN ACCURACY AND COMPUTATIONAL COST FOR DIFFERENT GLOBAL SPECTRAL MODELS

This paper presents an analysis of the performance of the three most common global spectral models for gas radiation, the weighted-sum-of-gray-gases (WSGG), the spectral line-based WSGG (SLW), and the full-spectrum k-distribution (FSK) models, when applied with the same number J of gray gases or quadrature nodes. The main purpose of the work is to assess and compare the accuracy of these models at a same level of computational cost. Values of J = 3 to J = 8 are considered. Decoupled, one-dimensional calculations on a purely H₂O participating medium are carried out, with the line-by-line (LBL) method serving as the reference. The rank-correlated approach is used for the SLW and FSK models, and new correlations based on a high-resolution database are generated for the WSGG model. Of the three models, the WSGG generally performs the worst, and the FSK, the best, even for J = 3. For this smallest J, the SLW model yields very large errors, but starting from J = 4 its accuracy is comparable to that of the FSK model. Increasing J tends to reduce the errors of these two models, but it has no effect on the WSGG model for J > 4.