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FLUENT on SHALE

FLUENT is a computational fluid dynamics solver that provides a wide array of advanced physical models for turbulence, combustion, and multiphase applications.

GAMBIT is a preprocessor for Fluent.

"The primary goals of running FLUENT in parallel are to reduce calculation turnaround time for complex problems by using multiple processors (CPUs) and to run large cases that cannot run on a single 32-bit processor. (A 32-bit processor can handle up to 2 – 3 million-cell cases)....." [1]

Running FLUENT under SHALE involves two steps:
  • Configuring a script file with TORQUE PBS commands.
  • Configuring a command file with FLUENT TUI commands.
Note: All GAMBIT models and mesh files must be generated on a separate workstation and transferred to SHALE.

Configuring a script file with TORQUE PBS commands

SHALE uses TORQUE,  "an open source resource manager providing control over batch jobs and distributed compute nodes"[2]

To submit a job, the qsub command must be executed, for example like:
qsub scriptfile
To run FLUENT on the SHALE cluster, the script file includes commands to assign a shell command, filenames and the total time the job should be allowed to run. Here are
the contents of a sample script file:

!/bin/bash
#PBS -S /bin/bash
#PBS -N fluentjobname
#PBS -e fluentjobname.err
#PBS -o fluentjobname.out
#PBS  -l walltime=24:00:00,nodes=8;ppn=2
np='wc -l < $PBS_NODEFILE'
fluent3d -t$np -mpi=net -cnf=$PBS_NODEFILE -g -i ~/path/fluentcommandfile.cmd

The first line specifies that the Bourne-again shell bash located in the /bin directory should be executed. Contact the system administrator if you plan on using other shell types
on the SHALE cluster.

Line's 2 through 6 start with the Portable Batch System (#PBS) commands.
Specifying the job name: replace jobname below with whatever your job is called.
#PBS -N jobname

Specifying the path/filename for standard output: Replace the path/outputfile with your path/filename.
#PBS -o path/outputfilename.out

Specifying the path/filename for standard error: Replace the path/errorfile with your path/filename.
#PBS -e path/errorfilename.err

Specifying the resource limits; max. wall clock time during which job can run/number of CPUs to be used: Contact the system 
administrator before changing the wall clock time. SHALE currently has a license to utilize 8 nodes with 2 processors per node, 
the "nodes=8; ppn=2" line should be left as is. 

#PBS -l walltime=24:00:00

The last line specifies which FLUENT solver is to be started. In this particular case the it is the 3D version. The other 
options are fluent2d, fluent2dpp, fluent3dpp for the 2D, 2D double precision and 3D double precision version. Refer to FLUENT 
user's manual for more options. 

fluent3d -t$np -mpi=net -cnf=$PBS_NODEFILE -g -i ~/path/fluentcommandfile.cmd

Replace the path and fluentcommandfile.cmd with your path and fluentcommandfile. 

The script file above was created using emacs/vi. Use your favourite editor to create yours!

Once your script file is ready, move on to the FLUENT command file that FLUENT will use to work on your .CAS and .DAT files.

References:
[1] FLUENT website
[2] TORQUE website