NEA-0443 FEM-2D.
FEM-2D, 2-D MultiGroup Diffusion in X-Y Geometry
NAME OR DESIGNATION OF PROGRAM, COMPUTER, NATURE OF PHYSICAL PROBLEM SOLVED, METHOD OF SOLUTION, RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM, TYPICAL RUNNING TIME, FEATURES, RELATED AND AUXILIARY PROGRAMS, STATUS, REFERENCES, MACHINE REQUIREMENTS, LANGUAGE, OPERATING SYSTEM OR MONITOR UNDER WHICH PROGRAM IS EXECUTED, ANY OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS, NAME AND ESTABLISHMENT OF AUTHOR, MATERIAL, CATEGORIES
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| Program name | Package id | Status | Status date |
|---|---|---|---|
| FEM-2D | NEA-0443/01 | Tested | 01-JUL-1978 |
Machines used:
| Package ID | Orig. computer | Test computer |
|---|---|---|
| NEA-0443/01 | CDC CYBER 173 | CDC CYBER 173 |
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4. METHOD OF SOLUTION
FEM-2D uses triangular elements with first and second order Lagrange approximations. The systems equations are formulated in multigroup form and solved by Cholesky procedure which operates only on nonzero elements. Various acceleration techniques are available for the outer iteration. Fluxes along various lines and rates in arbitrary zones may be output.
FEM-2D uses triangular elements with first and second order Lagrange approximations. The systems equations are formulated in multigroup form and solved by Cholesky procedure which operates only on nonzero elements. Various acceleration techniques are available for the outer iteration. Fluxes along various lines and rates in arbitrary zones may be output.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM
The code uses variable dimensioning. Thus, the problem size is restricted by the largest array which usually is the systems matrix. Fluxes of all groups are kept in memory. This might become another restrictive data set for a large number of groups. The validity of the results is restricted by the approximations used. FEM-2D requires a finite element net which allows the approximation of fluxes by at most parabolas. The node distribution should be more dense in areas of heavy flux changes (near absorbers or the reflector).
The code uses variable dimensioning. Thus, the problem size is restricted by the largest array which usually is the systems matrix. Fluxes of all groups are kept in memory. This might become another restrictive data set for a large number of groups. The validity of the results is restricted by the approximations used. FEM-2D requires a finite element net which allows the approximation of fluxes by at most parabolas. The node distribution should be more dense in areas of heavy flux changes (near absorbers or the reflector).
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6. TYPICAL RUNNING TIME
The running time is determined by the number of elements, the number of nodes and the approximation used. Due to the source and rate calculations, the number of nodes is the least important factor. Typical running times on a CDC 6600 for a two group problem are
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nodes elements approximation time/iteration (sec)
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177 301 first order 0.26
654 1204 first order 0.70
501 228 second order 0.48
654 301 second order 0.61
746 345 second order 0.70
The running time is determined by the number of elements, the number of nodes and the approximation used. Due to the source and rate calculations, the number of nodes is the least important factor. Typical running times on a CDC 6600 for a two group problem are
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nodes elements approximation time/iteration (sec)
------------------------------------------------------
177 301 first order 0.26
654 1204 first order 0.70
501 228 second order 0.48
654 301 second order 0.61
746 345 second order 0.70
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NEA-0443/01, included references:
- H.P. Franke and F.A.R. Schmidt:FEM2D - Program for Solving the Two-Dimensional Diffusion Equation by the
Method of Finite Elements
Progress Report of Research Task RB 78 I
July 1, 1974, Report Number 4-25 (ORNL-tr-2971)
- F.A.R. Schmidt and H.P. Franke:
Power Reactor Calculation with the Finite Elemen Program FEM 2D
Technical Notes (Reprint from Nucl. Sci. & Eng. 56, 431-433
- F.A.R. Schmidt:
FEM-2D - Input Description and Performance
March 1975, ike 4-43
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NEA-0443/01
| File name | File description | Records |
|---|---|---|
| NEA0443_01.001 | INFORMATION | 5 |
| NEA0443_01.002 | 'RSIMK' - SOURCE PROGRAM (F4+COMPASS) | 539 |
| NEA0443_01.003 | SOURCE PROGRAM (F4,COMPASS) | 4987 |
| NEA0443_01.004 | SAMPLE PROBLEM INPUT DATA | 62 |
| NEA0443_01.005 | SAMPLE PROBLEM PRINTED OUTPUT | 490 |
Keywords: Lagrange equations, diffusion equations, finite element method, power reactors, two-dimensional, x-y.