**RSICC CODE PACKAGE PSR-383**

**1. NAME AND TITLE**

KFIX-3D: Code System to Calculate 3D Extension 2-Phase Flow Dynamics.

**2. CONTRIBUTORS**

Los Alamos National Laboratory, Los Alamos, New Mexico through the Energy Science and Technology Software Center, Oak Ridge, Tennessee.

**3. CODING LANGUAGE AND COMPUTER**

FORTRAN IV; CDC7600 (P00383C760000).

**4. NATURE OF PROBLEM SOLVED**

This package consists of two programs K-FIX(3D) and K-FIX(3D, FLX) which extend the transient, two-dimensional, two-fluid program K-FIX to perform three-dimensional calculations. The transient dynamics of three-dimensional, two-phase flow with interfacial exchange are calculated at all flow speeds. Each phase is described in terms of its own density, velocity, and temperature. The application is to flow in the annulus between two cylinders where the inner cylinder moves periodically perpendicular to its axis. K-FIX(3D) is easily adaptable to a variety of two phase flow problems while K-FIX (3D,FLX) combines KFIX(3D), the three-dimensional version of the KFIX code, with the three-dimensional, elastic shell code FLX for application to a very specific class of problems. KFIX(3D,FLX) was developed specifically to calculate the coupled fluid-structure dynamics of a light water reactor core support barrel under accident conditions. Motion may be induced by blowdown, prescribed displacement, or seismic action.

This package was released by NESC in 1982 then transferred to ESTSC and then to RSICC in January 1999. Files were not retrievable from the media, but the NEA Data Bank in France graciously submitted their package which was obtained from NESC. Hence, the files in this package are from the NEADB NESC-0877/01 package.

**5. METHOD OF SOLUTION**

In K-FIX(3D), the six field equations for the two phases couple through mass, momentum, and energy exchange. The equations are solved using an Eulerian finite-difference technique that implicitly couples the rates of phase transitions, momentum, and energy exchange with determination of the pressure, density, and velocity fields. The implicit solution is accomplished iteratively without linearizing the equations, thus eliminating the need for numerous derivative terms. With the three-dimensional K-FIX code, calculations in Cartesian and cylindrical geometries can be performed. Obstacles built from the computing cells can be specified within the computing volume. In cylindrical geometry, calculations can be performed in the full 360 degrees or any angular segment. To enhance computing efficiency, a new cell indexing scheme has been introduced and computing time is reduced further by deletion of the viscous stress and heat conduction terms from the momentum and energy equations. FLX, which uses an explicit finite-difference solution algorithm to solve the shell equations, is explicitly coupled to the K-FIX(3D) fluid-dynamics program. A finite-difference numerical model is used for describing the dynamics of a core barrel.

**6. RESTRICTIONS OR LIMITATIONS**

None noted.

**7. TYPICAL RUNNING TIME**

The sample test problem for K-FIX(3D) requires 14 seconds to compile and less than one minute to execute on a CDC7600. The sample test problem for K-FIX(3D,FLX) requires 18 seconds to compile and less than 14 minutes to execute on a CDC7600.

**8. COMPUTER HARDWARE REQUIREMENTS**

The K-FIX(3D) sample problem, excluding plotting and timing routines, took about 50,000 (octal) words of small core memory (SCM) and 65,000 (octal) words of large core memory (LCM) storage.

**9. COMPUTER SOFTWARE REQUIREMENTS**

The code ran under SCOPE and required a FORTRAN IV compiler.

**10. REFERENCES**

"K-FIX(3D), NESC No. 877, K-FIX(3D) Tape Description, Implementation Information, and Supplementary Material," National Energy Software Center Note 82-01 (October 9, 1981).

W. C. Rivard, M. D. Torrey, "K-FIX: A Computer Program for Transient, Two-Dimensional, Two-Fluid Flow, THREED: An Extension of the K-FIX Code for Three-Dimensional Calculations," LA-NUREG-6623 (April 1977).

LA-NUREG-6623, Supplement I (March 1978).

LA-NUREG-6623, Supplement II (January 1979).

LA-NUREG-6623, Supplement III (July 1980).

J. K. Dienes, C. W. Hirt, W. C. Rivard, L. R. Stein, and M. D. Torrey, "FLX: A Shell Code for Coupled Fluid-Structure Analysis of Core Barrel Dynamics," NUREG/CR-0959, LA-7927 (November 1979).

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced documents and one diskette which includes source, job control language and test cases.

**12. DATE OF ABSTRACT**

April 1999.

** KEYWORDS:** FLUID DYNAMICS; REACTOR SAFETY