• Building the Programs
  1. Assumed Directories
  2. Unpacking the Source Files
  3. Setting Compile-Time Parameters
  4. Invoking the Makefile
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Building the programs

The following is a set of instructions for building the compressible-flow simulation program mb_cns.exe and its pre- and post-processors. The package should work on any UNIX-like platform with an ANSI C compiler.

The original development was done in a SUN OS environment at ICASE with the vectorisation tuned for Cray Y/MP and Cray 2 supercomputers. Further development was done under IBM AIX, HP/UX, Fujitsu VCC, IRIX, OS/2, Win32 systems, and (most recently) Linux.

As of August, 1998, the mb_cns, L1d, and ssp packages have been rearranged into a unified directory tree as described below.

Assumed Directories

The zip, tar and make files are set up assuming the following directory arrangement within the top level directory $HOME/cfd. Within that directory, mb_cns, L1d, nm, gas_models, util and plot packages each have a directory. Within the mb_cns directory the following subdirectories will exist:

• source
• unix
• borland
• tools
• examples
  • sod
  • sod2
  • cyl50
  • cone20
  • hemi2
  • a98
  • ...
• doc

Unpacking the Source Files

Set up a home directory named cfd and, put the tarred and gzipped files (mb_cns.tar.gz, cfd_util.tar.gz and cfd_plot.tar.gz) into the directory containing that cfd directory. Unzip this tar file and then extract all of the source and documentation files into their destination directories using

   % gzip -d mb_cns.tar
   % tar -xvf mb_cns.tar
   

   % tar --gunzip -xvf mb_cns.tar.gz
   

Within the directory, set up the other subdirectories as described above. It will be convenient to have $HOME/cfd_bin as part of your search path.

Up until the end of March 1998, source code development was done mainly on OS/2 and Win32 systems. If your computer doesn't like carriage returns and the Control-Z (end-of-file) character in the source files of earlier distributions, there is a shell script mb_cns/script/sc.sh that will remove these characters from text files. All of the files in the source directory can be processed using

   % cd source
   % ../script/sc.sh *
   

The executable files need to be built but, before doing so, check to see that the code is configured correctly and create the $HOME/cfd_bin directory if it is not already present.

Setting Compile-Time Parameters

Set the relevant macro-definitions in the header file compiler.h to reflect the compiler/ operating-system environment that you are using. Since many compilers now support the ANSI standard, there is little to choose from here. If one of the workstations is selected, that will probably cover most situations. The only special environments to note are the

CRAY_C

Cray vectorising compiler

VP_2600_C

Fujitsu VCC vectorising compiler

SGI_CHALLENGE

Power C analyser for the Silicon Graphics Power Challenge (shared memory).

Definitions in mb_cns.h which may need to be changed occasionally...

DEBUG_LEVEL

Set to 1 for occasional messages
Set to 2 for entry messages to all subroutines
Set to 3 dump detailed data as well
Set to 4 dump data within the flux calculation routines.

ECHO_ALL

Set to 1 to echo all input parameters as they are read
Set to 0 to NOT echo parameters.

INTERP_TYPE

Set to 0 for the high-order reconstruction to be third-order upwind-biased.
Set to 1 for fully-upwind high-order reconstruction.

STRINGENT_CFL

Normally set to 0.
However, for some viscous calculations with high aspect-ratio cells, it may need to be set to 1 to enforce a more restrictive CFL check on the time step.

PRINT_COUNT

Normally set to 20.
This is the number of time-steps between printing a status message to the console.

CFL_COUNT

Normally set to 10.
This is the number of time-steps between checking the size of the time-step.

Some definitions that should be left alone unless they cause trouble...

DOUBLE_PTR

When set to 1, two-dimensional arrays are allocated as pointers to pointers. This is the preferred option as the size of the data will adjust, at run time, to fit the size of grid requested.
When set to 0, two-dimensional arrays are allocated as single pointers. This is really only required for the Fujitsu VCC compiler which doesn't vectorise across rows of an array.
This parameter is set to 1 on selection of the Fujitsu VCC compiler in compiler.h.

NXDIM

Set to maximum size in ix index. This is needed only if DOUBLE_PTR == 0.

NYDIM

Set to maximum size in iy index. This is needed only if DOUBLE_PTR == 0.

NSPECD

Set to the maximum number of species used in the gas model. For single species calculations, leave it as 2 if memory is not a problem.

NGHOST

Default value = 2.
Number of ghost (or buffer) cells surrounding the active cells within a block.

NDIM

Length of temporary vectors. It needs to be large enough to accommodate the largest grid dimension (plus 4 elements for ghost cells). On Intel (PC) class machines, this dimension should be kept as small as reasonable because of the small cache size and slow main memory. For example, running the cone20 test case with NDIM=504 rather than NDIM=204 resulted in a 37% increase in CPU time.

BLOCK_DIM

Maximum number of blocks that will be used.

NL

Number of levels in the time-stepping procedure. Leave as 2 for the standard predictor-corrector scheme.

VERY_SMALL (in cns_visc.c)

Smallest value of y for the axisymmetric terms.

QUICK_AND_DIRTY (in rivp.c)

Use the approximate power macro qd_power.h

LINEAR (in rivp.c)

Type of interpolation used within the rarefactions.

NN (in mb_hist.c)

The maximum number of history events that can be picked up by mb_hist. The value 10000 should be enough for most applications.

BEZIER_DIM (in mb_prep.c)

Maximum number of Bezier segments in a Bezier polyline. The value 20 should be plenty for most applications.

MAX_LINES (in mb_prof.c)

The maximum number of strips that can be pasted together when extracting a flow profile.

RHOMIN, EMIN, PMIN, TMIN, AMIN (in gas.c)

As a brute-force way of making the code robust in extreme flow situations, certain elements of the gas state are limited to small positive (and physically meaningful) values. These lower limits are set in gas.c and may need to be adjusted if you are simulating (what may be) unusual flow conditions. One such condition might be a rarefied flow where all of the densities are very small. This is one of the disadvantages of using dimensional quantities within the code.

CHECK_RECONSTRUCTION_FAILURE (in mb_cns.h)

If set to 1, the high-order reconstruction will be checked to see if it has provided reasonable estimates for the Left and Right cell interface properties. The loops in this section of code are not easy to vectorise so, for vector computers such as Cray C90 and Fujitsu VP, it may be preferable to turn this checking off.

WARN_RECONSTRUCTION_FAILURE (in mb_cns.h)

If set to 1 (and high-order reconstructions are checked), warnings will be logged whenever the high-order reconstruction fails to give reasonable estimates.

CHECK_FOR_VALID_DATA, MAX_INVALID_CELLS (in mb_cns.h)

When decoding the array of conserved quantities, the specific internal energy or the density may try to go negative. If it does, the value is reset to small positive value inside decode_conserved() and, if CHECK_FOR_VALID_DATA == 1, the number of cells in which this happens is counted. MAX_INVALID_CELLS is the maximum number of cells (per block) for which this event will be tolerated. If this symptom occurs, your best bet is to refine the grid so that the cells are not too elongated and that sharp expansion corners are avoided.

DT_REDUCTION_FACTOR (in mb_cns.h)

If an attempt at a time step fails because of invalid cells, the time step is re-attempted with a smaller time step. A reduction factor of 0.2 is somewhat arbitrary. A factor of 0.5 would seem to be not enough but a factor of 0.1 would seem too expensive.

Invoking the Makefile

Change to the source directory and build the executable programs by invoking the make file and specifying the target computer. For example, the programs can be built for a UNIX workstation with the GNU C compiler using

% make for_gnu

% make for_sg_mp

% make install

At this point you should have a complete set of executables in the $HOME/cfd_bin directory and you are now ready to try running them.