Development of a Discrete Ordinates Code System for Unstructured Meshes of Tetrahedral Cells, with Serial and Parallel Implementations

A numerically stable, accurate, and robust form of the exponential characteristic (EC) method, used to solve the time-independent linearized Boltzmann Transport Equation, is derived using direct affine coordinate transformations on unstructured meshes of tetrahedra. This quadrature, as well as the linear characteristic (LC) spatial quadrature, is implemented in our transport code, called TETRAN. This code solves multi-group neutral particle transport problems with anisotropic scattering and was parallelized using High Performance Fortran and angular domain decomposition. A new, parallel algorithm for updating the scattering source is introduced. The EC source and inflow flux coefficients are efficiently evaluated using Broyden's rootsolver, started with special approximations developed here. TETRAN showed robustness, stability and accuracy on a variety of challenging test problems. Parallel speed-up was observed as the number of processors was increased using an IBM SP computer system.Air Force Inst of Tech Wright-Patterson AFB OH School of Engineering is the author of 'Development of a Discrete Ordinates Code System for Unstructured Meshes of Tetrahedral Cells, with Serial and Parallel Implementations', published 1998 under ISBN 9781423555841 and ISBN 1423555848.