47th AIAA Aerospace Sciences Meeting and Exhibit, 5-8 Jan 2009, Orlando, Florida Correlated-k Distribution Method for Atomic Radiation in Hypersonic Nonequilibrium flows Ankit Bansal * , M. F. Modest † and D. A. Levin ‡ Department of Mechanical Engineering Department of Aerospace Engineering The Pennsylvania State University, University Park, PA 16802 I. Abstract Radiation from the shock layer during atmospheric entry plays a significant role in the design of modern space vehicles, particularly in the design of the thermal protection system. This makes it necessary to predict the effects of radiation accurately and, at the same time, efficiently for the optimum design of new generation space vehicles. Line-by-line calculations are the most accurate method to solve the radiative transfer equation (RTE); however, they are not practical because of their large computational cost. In this work a correlated- k distribution method has been developed for the most important atomic species (N and O, as well as their ions), which provides great accuracy with high numerical efficiency for the evaluation of radiative transfer in a hot plasma. Challenges posed by typical nonequilibrium gas conditions in the plasma were overcome by splitting the full spectrum into a number of nonoverlapping part-spectra. Results for one-dimensional inhomogeneous gas slabs are presented and compared with line-by-line benchmarks and the full-spectrum correlated-k (FSCK) model, showing very good accuracy in typical nonequilibrium gas conditions as are found in atmospheric reentry of space vehicles. Nomenclature a nongray stretching function of k-distributions, dimensionless b line width, Å c speed of light, 2.9979 × 10 8 ms -1 f k-distribution, cm g, g 0 cumulative k-distribution h Planck’s constant, 6.6262 × 10 -34 Js I intensity, (W/m 2 cm) k reordered absorption coefficient, cm -1 m atomic mass, kg N, N number density (vector) T temperature, K V volume, m 3 Greek κ absorption coefficient, cm -1 λ wavelength, Å * Graduate student, Department of Mechanical Engineering; azb162@psu.edu † Distinguished professor, Department of Mechanical Engineering; mfm@engr.psu.edu ‡ Professor, Department of Aerospace Engineering; dalevin@psu.edu 1 47th AIAA Aerospace Sciences Meeting Including The New Horizons Forum and Aerospace Exposition 5 - 8 January 2009, Orlando, Florida AIAA 2009-1027 Copyright © 2009 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.