NESC0859 SOLA-LOOP.

1. NAME OR DESIGNATION OF PROGRAM:  SOLA-LOOP.

3. DESCRIPTION OF PROBLEM OR FUNCTION

SOLA-LOOP is designed for the solution of transient two-phase flow in networks composed of one- dimensional components. The fluid dynamics is described by a non- equilibrium drift-flux formulation of the fluid conservation laws.
Although developed for nuclear reactor safety analysis, SOLA-LOOP may be used as the basis of other types of special-purpose network codes. The program can accommodate almost any set of constitutive relations, property tables, or other special features required for different applications.

4. METHOD OF SOLUTION

The drift-flux equations are formulated as continuity equations, the momentum equation, and the internal energy equation. The mixture density, the macroscopic vapor density, the center of mass velocity, and the mixture specific internal energy are chosen as dependent variables, and time and axial position are the independent variables. Constitutive relations and exchange rates are determined by the intended use of the code. The calculation cycle used to solve by point relaxation methods the finite difference formulation of the flow equations in a single one- dimensional component is made up of four tasks. First, the momentum  equation is advanced explicitly using the values from the previous cycle for all contributions. Next, an iteration is made to replace the pressure with advanced time values. This pressure iteration scheme is a variant of the implicit continuous fluid Eulerian (ICE)  technique.
Then, all other dependent variables are updated, and in the fourth task data output, time-step control, and housekeeping operations are performed. Various boundary conditions may be applied at the ends of the one-dimensional component meshes to represent inlet and exit conditions including prescribed velocities or pressures, uniform or  gradient-free outflow, and periodic boundaries in which the bottom and top of a component are joined. Where two or more components are  coupled, special coupling equations are solved to obtain the appropriate boundary conditions for each. Different time-steps can be used in various components. The time-steps are determined by numerical stability requirements and other user-supplied conditions.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Conservation of momentum is not required by the finite difference approximations used for the momentum equation. Current dimensioning in the SOLA- LOOP program allows maxima of
     10 components
      8 segments per component
    200 junctions
6 time levels, pressure groups, and vapor production rates per         cell
      5 boundary data sets.
These restrictions may be adjusted by changing the values of the variables NP, NS, NJ, NK, and NM, respectively, and all appropriate  DIMENSION statements.

6. TYPICAL RUNNING TIME

The time required is highly problem- dependent. NESC executed the sample problem in less than 3 CP minutes on a CDC 7600.

7. UNUSUAL FEATURES OF THE PROGRAM

Network systems often contain low- speed flow with slowly-varying properties in one region and high- speed flow or flow that requires a finely-detailed description in another. The variable time-steps and subcycling provisions in SOLA-  LOOP are designed specifically for such systems.

8. RELATED AND AUXILIARY PROGRAMS

The solution algorithm has evolved  from earlier SOLA series programs. The original SOLA was designed for problems involving a single incompressible fluid in a fixed- region. SOLA-LOOP is an advanced network code derived from the SOLA- DF (NESC Abstract 832) code, which is based on a drift-flux approximation for the dynamics of a two-phase mixture.
K-FIX (NESC Abstract 727) and K-TIF (NESC Abstract 876) are detailed models for transient, two-phase flows in two and three dimensions.

10. REFERENCES

- C.W. Hirt, N.C. Romero, M.D. Torrey, and J.R. Travis:
  SOLA-DF: A Solution Algorithm for Nonequilibrium Two-Phase Flow
  NUREG/CR-0690 (LA-7725/MS), June 1979.
- C.W. Hirt, B.D. Nichols, and N.C. Romero:
  SOLA - A Numerical Solution Algorithm for Transient Fluid Flow
  LA-5852, April 1975.

- C.W. Hirt, T.A. Oliphant, W.C. Rivard, N.C. Romero, M.D. Torrey:
  SOLA-LOOP, A Nonequilibrium Drift-Flux Cpde for Two-Phase Flow in
  Networks
  NUREG/CR-0626 LA-7659 R-4 (June 1979).
- C.W. Hirt, T.A. Oliphant, W.C. Rivard, N.C. Romero, M.D. Torrey:
  SOLA-LOOP, A Nonequilibrium Drift-Flux Cpde for Two-Phase Flow in
  Networks
  NUREG/CR-0626 LA-7659 R-4 (June 1979).

11. MACHINE REQUIREMENTS

34,000 (octal) words of memory are needed to  execute the program.

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:  SCOPE.

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

Because of computing environment differences the time-step/subcycle  sequence used by SOLA-LOOP is likely to produce slightly varying results on different computer systems.

15. NAME AND ESTABLISHMENT OF AUTHOR

C.W. Hirt, T.A. Oliphant, W.C. Rivard, N.C. Romero, and M.D. Torrey* Los Alamos National Laboratory
P. O. Box 1663
Los Alamos, New Mexico 87545, U.S.A.

* Contact

       Centro Atomico Bariloche
       8400 BARILOCHE
       ARGENTINA

Solaloop.for Source code
Solaloop.ar Input file

File name	File description	Records
NESC0859_02.001	Information file	32
NESC0859_02.002	SOLA-LOOP source program (FORTRAN)	4044
NESC0859_02.003	SOLA-LOOP test case input data	22
NESC0859_02.004	SOLA-LOOP test case printed output	1052