Improved Discrete Ordinates Calculations for an Approximate Model of Neutral Particle Transport in Ducts

摘要

An imporoved implementation of the discrete ordinates method for computing neutral particle transport in ducts is presented. The considered one-dimensoanl model makes use of two basis functions to represent the transverse and azimuthal depdnecies of the particle angular flux in the duct. It is shown that if the problem is decomposed into uncollided and collided problems prior to using the discrete ordinates approximation, the number of a ordinates necessary to achieve a desired degree of accuracy in the solution can be greatly reduced, especially for long ducts with signficant wall absorption. Further savings in computer time can be attained by employing a composite quadrature based on a (nonstandard) halfrange quadrature that can be generated in an effective and efficient way with one of the classical mehtods in the constructive theory of orthogonal polynomials.