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Manuscript Title: ESECT/EMAP: mapping algorithm for computing intersection volumes of overlaid meshes in cylindrical geometry.
Authors: B.R. Wienke
Program title: ESECT/EMAP
Catalogue identifier: AAFD_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 39(1986)259
Programming language: Fortran.
Computer: CRAY-1S.
Operating system: CTSS.
RAM: 13K words
Word size: 64
Keywords: Radiation physics, Eulerian-lagrangian Mesh mapping, Intersection volumes, Volume weighting.
Classification: 21.1.

Nature of problem:
ESECT and EMAP are routines which provide an algorithm for mapping arbitrary meshes onto rectangular meshes in cylindrical (r,z) geometry. Intersection volumes between two meshes are computed and stored along with two indices tagging the intersection zones on each mesh. Input consists of the lines defining the rectangular mesh and the coordinates of the arbitrary mesh, which are assumed to be joined by straight lines. Output consists of the intersection volumes with designation of common mesh zones. Three intersection volumes can be used to smear material properties, energy densities, fluxes, temperatures and related quantities across two meshes in coupled hydro-dynamics and transport applications.

Solution method:
Exact expressions for the volumes of rotation (about z-axis) generated by the planar mesh intersection areas are obtained by triangulation. Intersection points of the two meshes are computed and mapped onto corresponding regions on the rectangular mesh. Intersection points with the same regional indices are reordered into multilaterals and the multilaterals triangulated to facilitate computation of the intersection volumes.

Running time:
Computations of intersection volumes generated by overlapping 10K rectangular and 2.2K radial meshes require an average of 9 s computer time, while computation times for the same mashes scaled by a factor of 1/4 in number of grid points average 1 s on the CRAY's. The arbitrary meshes employed in the calculations are symmetrical center converging webs of 5 degrees and 20 degrees segments, respectively, with the largest number of cells near the center of convergence. The rectangular meshes are uniform. Generally, cases of small cell rectangular meshes overlaid on large cell arbitrary meshes require the longer running times.