NESC0858 APACHE.

1. NAME OR DESIGNATION OF PROGRAM:  APACHE.

3. DESCRIPTION OF PROBLEM OR FUNCTION

APACHE is a time-marching finite-difference code developed to solve the equations of transient viscous multicomponent chemically reactive fluid dynamics in two space dimensions. A steady-state solution is obtained as the asymptotic limit of a transient calculation.

4. METHOD OF SOLUTION

APACHE utilizes an Eulerian mesh with cells that are arbitrary trapezoids. It can be run in a purely explicit mode or a partially implicit mode. The explicit mode is an explicit  difference scheme with primary stability limitation, the Courant- Friedrichs-Lewy condition that an acoustic signal cannot traverse more than one spatial increment per cycle. The partially implicit mode is a variant of the ICE method with primary stability limitation that the fluid cannot traverse more than one spatial increment per cycle. It is primarily useful for low Mach number. The difference approximation to the convective terms is obtained by the  tensor viscosity method to achieve numerical stability without excessive damping. Multicomponent diffusion in APACHE is calculated  by a self-consistent effective binary diffusion algorithm.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

The fluid is assumed to be an ideal-gas mixture with temperature-independent specific heats. Chemical reactions are assumed to be elementary. Current dimensioning in the program allows only one rotational and vibration level of the lasing species to be considered and a maxima of -
    1 chemical reaction
   10 chemical species
   32 cells in the horizontal direction
   22 cells in the vertical direction.
These restrictions may be increased by increasing the value of the appropriate parameter variables and the corresponding DIMENSION statements.

6. TYPICAL RUNNING TIME

The running time varies from several minutes  for very simple problems to two hours for complex ones. NESC executed the sample problem in less than 2 CP minutes on a CDC 7600.

7. UNUSUAL FEATURES OF THE PROGRAM

Geometrical specifications, initial conditions, and boundary conditions are localized in user- input subroutines. The governing equations are written in two- dimensional variable-depth form, which allows the calculation of flow confined between two free-slip walls of variable spacing. Planar and cylindrical geometries are special cases of the variable- depth description. A spatial marching option reduces the computer time needed for steady-state supersonic flow calculations. For applications to CW chemical lasers, a subroutine calculates radiation intensities and laser power in the Fabry-Perot cavity approximation. The partially-generalized spatial mesh allows the convenient representation of curved boundaries and also provides variable zoning.

8. RELATED AND AUXILIARY PROGRAMS

APACHE is applicable to problems similar to those solved by RICE (NESC Abstract 720), but provides greater geometrical flexibility.

10. REFERENCES

- J.D  Ramshaw and J.K. Dukowicz:
  APACHE: A Two-Dimensional Reactive Fluid Dynamics Code for
  Chemical Laser Applications
  LA-UR-78-2765, November 1978.
- Otis A. Farmer and John D. Ramshaw:
  A Method for Rapid Attainment of the Steady-State in Two-
  Dimensional Time-Marching Supersonic Flow Calculations
  Journal of Computational Physics, Vol. 24, No. 1, pp 23-28,
     May 1977, (Appendix A of LA-7427).
- John D. Ramshaw, Raymond C. Mjolsness, and Otis A. Farmer:
  Numerical Method for Two-Dimensional Steady-State Chemical Laser
  Calculations
  Journal of Quantitative Spectroscopy and Radiative Transfer
Vol. 17 No. 2, pp. 149-164, February 1977, (Appendix B of LA-7427)  - J.K. Dukowicz and J.D. Ramshaw:
Tensor Viscosity Method for Convection in Numerical Fluid Dynamics    Journal of Computational Physics, Vol. 32, No. 1, pp. 71-79,
    July 1979.

- J.D  Ramshaw and J.K. Dukowicz:
  APACHE: A Generalized-Mesh Eulerian Computer Code for Multi
  Component Chemically Reactive Fluid Flow
  LA-7427 (January 1979).
- S.T. Bennion:
  J526 Convert Coordinate
  LASL Program Library Write-up (January 1979).
- R. Elliot:
  J516 Plot a Point
  LASL Program Library Write-up (January 1979).
- Gene Willbanks:
  J520 Types Specific Point on Film
  LASL Program Library Write-up (January 1979).
- R. Elliot:
  J522 Types Specific Point Vertically
  LASL Program Library Write-up (January 1979).
- J506 Manupulates Microfilm
  LASL Program Library Write-up (January 1979).
- Modification of LA-7427 Input Description
  NESC Note 80-30 (December 17, 1979).

11. MACHINE REQUIREMENTS

APACHE requires 33,000 (octal) words of small core memory and 56,000 (octal) words of large core memory.

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

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

NESC included dummy routines for the Stromberg-Carlson Plotter routines: ADV, CONVRT, DRV, LINCNT, PLT, SPLOT, TSP, and TSPV, and for the following LANL graphics initialization and buffering routines: GRF80, GRPHFTN, GRPHLUN, LIB4020, and SETFLSH. Alternative routines for the computer environment in which the program is being  executed are required to obtain graphical output.
Subroutines GEOM, INITIAL, and BNDARY in APACHE are user-input routines specific to the sample problem. Changes will be required for other problems.

15. NAME AND ESTABLISHMENT OF AUTHOR

J.D. Ramshaw and J.K. Dukowicz
Los Alamos National Laboratory
P. O. Box 1663
Los Alamos, New Mexico 87545, U. S. A.

File name	File description	Records
NESC0858_01.001	SOURCE	4670
NESC0858_01.002	SOURCE	3310
NESC0858_01.003	S.P. INPUT	11
NESC0858_01.004	S.P. OUTPUT	3887