Acceleration schemes for the discrete ordinates method
- Babcock and Wilcox, Alliance, OH (United States). Research and Development Div.
In many combustion devices such as furnaces and burners, radiant heat transfer is the dominant mode of heat transfer and significantly affects the gas and wall temperature distributions. Because reaction rates and density distributions are closely linked to the local gas temperatures, radiation heat transfer plays a large role in governing the combustion dynamics. As a consequence, accurate prediction of the performance of practical combustion devices requires robustly converging methods for solving the radiative transport equation. Discrete ordinates methods have been developed to solve the multidimensional radiative transport equation (RTE) for applications including combustion processes and other combined-mode heat transfer cases. The convergence of discrete ordinates methods is known to degrade for optical thicknesses greater than unity, which occur for example in a flame. Acceleration schemes have been developed for use in neutron transport applications, but little work has been done to accelerate convergence of the RTE for radiative heat transfer applications. This paper presents several acceleration schemes for the RTE, including successive overrelaxation, synthetic acceleration and mesh rebalance methods. Solution convergence is discussed and demonstrated using two- and three-dimensional examples. While all methods improve convergence, the mesh rebalance method improves the RTE convergence best. For some conditions, rebalance methods can improve convergence dramatically, reducing RTE iterations by an order of magnitude. However, the mesh rebalance method fails to produce convergence of the RTE for large optical thicknesses and fine mesh discretizations. Examples are used to demonstrate that improved convergence can be obtained by solving the rebalance equation on a coarser grid, which is determined by regrouping the base RTE grid, until an optical thickness of near unity is obtained on the coarse grid.
- OSTI ID:
- 455357
- Report Number(s):
- CONF-950828--; ISBN 0-7918-1714-8
- Country of Publication:
- United States
- Language:
- English
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