TY - JOUR
T1 - Comparative analysis of reduced-order spectral models and grouping strategies for non-equilibrium radiation
AU - Sahai, Amal
AU - Johnston, Christopher O.
AU - Lopez, Bruno
AU - Panesi, Marco
N1 - Funding Information:
This research has been supported under a NASA Early Career Faculty Award (grant number NNX15AU4-4G ).
Publisher Copyright:
© 2019 Elsevier Ltd
PY - 2020/2
Y1 - 2020/2
N2 - Radiative transfer calculations in complex three-dimensional domains are plagued by computational bottlenecks due to the combined cost of resolving spectral, angular, and spatial dependence. The current work presents a systematic study into the efficacy of three commonly used reduced-order wide-band models, Planck-averaging, and statistics-based k-distribution and theory of homogenization, for modeling non-equilibrium radiation. A reinterpretation of Planck-averaging based on the maximum entropy principle combined with the commonly used multi-band opacity binning allows a direct equivalence to be drawn with the two statistics-based approaches. Additionally, the three seemingly distinct methods are shown to be strictly derived only for local thermodynamic equilibrium conditions which limits their accuracy when simulating non-equilibrium radiation. This shortcoming is addressed through the development of a novel grouping strategy for defining larger groups of individual frequencies from detailed radiation databases (based on line-by-line or narrow-band models) while accounting for variation in all radiative properties under non-equilibrium. Radiative transfer calculations for different Earth and Jupiter entry problems are performed using the different spectral models. Conventional reduced-order wide-band approaches converge slowly to the solution obtained using detailed spectral models. However, the new non-equilibrium grouping strategy allows both total quantities-of-interest and their detailed spectral variation to be predicted accurately while employing fewer reduced-order groups. The current model-reduction methodology provides nearly two orders-of-magnitude decrease in required spectral evaluations along a given line-of-sight with respect to narrow-band methods (and three to four orders with respect to original LBL databases) and is ideal for coupled flow-radiation calculations.
AB - Radiative transfer calculations in complex three-dimensional domains are plagued by computational bottlenecks due to the combined cost of resolving spectral, angular, and spatial dependence. The current work presents a systematic study into the efficacy of three commonly used reduced-order wide-band models, Planck-averaging, and statistics-based k-distribution and theory of homogenization, for modeling non-equilibrium radiation. A reinterpretation of Planck-averaging based on the maximum entropy principle combined with the commonly used multi-band opacity binning allows a direct equivalence to be drawn with the two statistics-based approaches. Additionally, the three seemingly distinct methods are shown to be strictly derived only for local thermodynamic equilibrium conditions which limits their accuracy when simulating non-equilibrium radiation. This shortcoming is addressed through the development of a novel grouping strategy for defining larger groups of individual frequencies from detailed radiation databases (based on line-by-line or narrow-band models) while accounting for variation in all radiative properties under non-equilibrium. Radiative transfer calculations for different Earth and Jupiter entry problems are performed using the different spectral models. Conventional reduced-order wide-band approaches converge slowly to the solution obtained using detailed spectral models. However, the new non-equilibrium grouping strategy allows both total quantities-of-interest and their detailed spectral variation to be predicted accurately while employing fewer reduced-order groups. The current model-reduction methodology provides nearly two orders-of-magnitude decrease in required spectral evaluations along a given line-of-sight with respect to narrow-band methods (and three to four orders with respect to original LBL databases) and is ideal for coupled flow-radiation calculations.
KW - Grouping strategy
KW - Non-equilibrium
KW - Reduced-order method
KW - Spectral model
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U2 - 10.1016/j.jqsrt.2019.106752
DO - 10.1016/j.jqsrt.2019.106752
M3 - Article
AN - SCOPUS:85075149897
SN - 0022-4073
VL - 242
JO - Journal of Quantitative Spectroscopy and Radiative Transfer
JF - Journal of Quantitative Spectroscopy and Radiative Transfer
M1 - 106752
ER -