Journal of Quantitative Spectroscopy & Radiative Transfer 245 (2020) 106857 Contents lists available at ScienceDirect Journal of Quantitative Spectroscopy & Radiative Transfer journal homepage: www.elsevier.com/locate/jqsrt Locally correlated SLW model for prediction of gas radiation in non-uniform media and its relationship to other global methods Vladimir P. Solovjov a , Brent W. Webb a,∗ , Frederic André b , Denis Lemonnier c a Brigham Young University, 360G EB, Provo, UT 84602, USA b Univ Lyon, CNRS, INSA-Lyon, Université Claude Bernard Lyon 1, CETHIL, 5008 Villeurbanne, France c ISAE-ENSMA, BP 40109, 86961 Futuroscope Chasseneuil Cedex, France a r t i c l e i n f o Article history: Received 15 November 2019 Revised 13 January 2020 Accepted 25 January 2020 Available online 28 January 2020 Keywords: gas radiation global models SLW model FSCK model a b s t r a c t Following previous theoretical development based on the assumption of a rank correlated/comonotonic spectrum, the Locally Correlated SLW (LC-SLW) method is outlined. The relationship between the LC-SLW method and the Reference Approach SLW (RA-SLW) method and the Rank Correlated SLW method (RC- SLW) is established. Further, the relationship between these SLW model variants and other global models including the Full Spectrum Correlated-k (FSCK) and Absorption Distribution Function (ADF) models is defined. The predictive accuracy of the various SLW models is compared. It is found that, despite the fact that the RC-SLW model demonstrates better overall accuracy, the LC-SLW model may generally prove more accurate in regions of higher gas temperature. While the LC-SLW model yields improved accuracy over the RC-SLW model in regions of high temperature, it is shown that the LC-SLW model cannot claim universal improvement in predictive accuracy at all conditions. © 2020 Elsevier Ltd. All rights reserved. 1. Introduction Global methods are presently the most computationally effi- cient methods for modeling thermal radiation transfer in high temperature non-uniform gaseous media [1]. These methods in- clude the SLW (Spectral Line Weighted-sum-of-gray-gasses) [2,3], ADF (Absorption Distribution Function) [4], FSK (Full Spectrum k-distribution) [5], SLMB (Spectral Line Moment-Based) [6], and WSGG (Weighted-Sum-of-Gray-gasses) [7] models. The models have been demonstrated capable of providing predictive accuracy approaching that of rigorous line-by-line method (LBL) but at dra- matically lower computational cost. Despite the seeming difference between the SLW, ADF, and FSK methods, they are all based on the same fundamental principle in modeling of the gas absorption spectrum, and it has previously been shown that all can be de- scribed as particular cases of the Generalized SLW Model [8]. Different approaches for SLW modeling in non-uniform media are based on the assumption of either correlated/comonotonic or scaled spectra. Eight possible correlated SLW approaches have been developed theoretically in [8,9]. However, not all of them have been evaluated from the perspective of predictive accuracy. The various global methods, which are theoretically equivalent if the ∗ Corresponding author. E-mail address: webb@byu.edu (B.W. Webb). gas absorption spectra are rigorously correlated or scaled, can yield different predictions for radiative transfer in non-uniform real gas scenarios. Each approach has its unique advantages and disadvan- tages. Even the RC-SLW method [9–11], which has been shown to be theoretically superior to other approaches [10], has inher- ent limitations and may not be universally preferred in all situa- tions. This paper investigates the so-called locally correlated mod- els, where the correlation between absorption spectra at different states is established at the local blackbody source temperature T loc rather than at a fixed (reference) temperature T b (as is done in the traditional RA-SLW, RC-SLW, and ADF methods). Although the four possible versions of the locally correlated SLW model were intro- duced previously [8,9], they have not been explored in detail. The approach used in [12,13] may be loosely interpreted as a locally correlated model. Those studies presented the SLW version of the improved FSK method of Cai and Modest [14], which technically is also a locally correlated approach for which no rigorous derivation or theoretical justification was reported. The present paper intends to describe in detail and to study the most efficient version of the locally correlated SLW model, to establish its relationship to the reference approach SLW and rank correlated SLW models, to illustrate the relationship between the locally correlated SLW model and other global methods (ADF, FSK), and to explore the predictive accuracy of the various SLW models for a set of example problems investigating scenarios of gas ab- sorption or emission dominance. https://doi.org/10.1016/j.jqsrt.2020.106857 0022-4073/© 2020 Elsevier Ltd. All rights reserved.