1. NAME AND TITLE

FEWA-FEMA: A Finite Element Model of Water and Other Material through Aquifers.

2. CONTRIBUTOR

Oak Ridge National Laboratory, Oak Ridge, Tennessee.

3. CODING LANGUAGE AND COMPUTER

Fortran IV; IBM 3033.

4. NATURE OF PROBLEM SOLVED

FEWA is a finite element model designed to treat complex transient real-world problems of sources/sinks, Dirichlet boundary values, Neumann or Cauchy fluxes, and leaky confining beds (aquitards) simultaneously.

FEMA deals with the construction, verification, and demonstration of a finite element model of material transport through aquifers. The particular features of FEMA are its versatility and flexibility to deal with as many real-world problems as possible.

5. METHOD OF SOLUTION

In FEWA, both quadrilateral and triangular elements, or a combination of the two, are used to facilitate the discretization of a compound region with highly irregular curved boundaries. Also, a pointwise iteration solution strategy for solving the matrix equation approximating the partial differential equation is included as an alternative to the direct solution method. This inclusion makes the model efficient and applicable to large-field problems when the bandwidth of the matrix becomes large.

Three optional sorption models are embodied in FEMA. These are linear isotherm and Freundlich and Langmuir nonlinear isotherms. Point as well as distributed source/sinks are included to represent artificial injection/withdrawals and natural infiltration of precipitation. All source/sinks can be transient or steady state. Finite element methods are adopted to transform the governing differential equations to the matrix equation. To increase the applicability of the model in terms of stability and convergence, twelve options have been included for the derivation of the matrix equation. The resulting matrix equation is solved with either the direct elimination or successive relaxation technique.

6. RESTRICTIONS OR LIMITATIONS

None noted.

7. TYPICAL RUNNING TIME

FEWA-FEMA runs in < 20 cpu sec.

8. COMPUTER HARDWARE REQUIREMENTS

FEWA-FEMA is operable on the IBM 3033 computers. Input/output is < 1000.

9. COMPUTER SOFTWARE REQUIREMENTS

FEWA-FEMA was written in Fortran H. The FEWA sample problem uses a 508 K region and the FEMA sample problem uses 268 K.

10. REFERENCES

G. T. Yeh and D. D. Huff, "FEWA: A Finite Element Model of Water Flow Through Aquifers," ORNL-5976 (November 1983).

G. T. Yeh and D. D. Huff, "FEMA: A Finite Element Model of Material Transport Through Aquifers," ORNL-6063 (January 1985).

11. CONTENTS OF CODE PACKAGE

Included are the referenced documents and one (1.2MB) DOS diskette which contains the source code and sample problem input.

12. DATE OF ABSTRACT

June 1986.