Coupling the DOT-IV two-dimensional discrete ordinates transport computer code through a 90-degree rotation of geometry

COUPL is a FORTRAN computer code designed to couple together two DOT-IV¹ discrete ordinates transport problems through a region where the r-z geometry is rotated 90 degrees. A typical case of this situation is the test problem in this report as depicted in Fig. 1 where two DOT-IV calculations are coupled through a 90-degree piping elbow (two-legged duct). COUPL is applicable to other problems of this type as long as the diameter of leg 2 is less than or equal to the diameter of leg 1.

COUPL reads the solutions calculated by the DOT-IV code in the region of interest of leg 1 and writes a boundary source, consisting of directional fluxes, on a specified r-Θ (z boundary) surface in leg 2. This boundary source serves to start the leg 2 DOT-IV calculation and thus continue the solution of the piping elbow transport problem by producing reasonable solutions throughout leg 2.

After a brief discussion of the nature of the transport problem and the application of the DOT-IV code, and after outlining the requirements for the DOT-IV boundary source and characteristics of the DOT-IV VARFLM flux and moment output, a description of the transformation techniques as used in COUPL will follow. Finally, the sample problem (Fig. 1) on which the code has been tested will be discussed and the corresponding results will be compared with a Monte Carlo estimate. The comparison indicates that COUPL is a convenient and reasonably accurate means of effecting such a rotation in geometry in a transport problem, and is considerably less expensive than performing the same calculation by Monte Carlo.