Over the past two weeks we have experienced Oakely login node crashes potentially caused by a Lustre bug.


FLUENT is a state-of-the-art computer program for modeling fluid flow and heat transfer in complex geometries.


Availability & Restrictions

FLUENT is available on both the Glenn and Oakley clusters.  The following versions are available:

13 X X
14 X  
14.5   X

A base license token will allow Fluent to use up to 4 cores without any additional tokens. If you want to use more than 4 cores, you will need an additional "HPC" token per core. For instance, a serial FLUENT job with 1 core will need 1 base license token while a parallel FLUENT job with 8 cores will need 1 base license token and 4 HPC tokens.

Academic License Limitations

Currently, there are in total 25 base license tokens and 68 HPC tokens for academic users. These HPC tokens are shared between FLUENT and ANSYS. A job using a base license token can be submitted to either Glenn or Oakley clusters. A parallel job using HPC tokens (with "ansyspar" flag) however can only be submitted to Glenn clusters due to scheduler issue.

NDEMC License Limitations

For NDEMC users, there are in total 10 base license tokens and 512 HPC tokens. These HPC tokens are shared among available ANSYS products (FLUENT, CFX, ICEMCFD, ANSYS Mechanical, etc.) All jobs should be submitted to Oakley cluster. 



Use of FLUENT for academic purposes requires validation. To obtain validation please complete and return the "Academic Agreement to Use FLUENT." This can be obtained from your site consultant or from the files fluent.pdf located in the Academic Agreement Forms.


FLUENT can only be run on the compute nodes of the Oakley and Glenn clusters. Therefore, all FLUENT jobs are run via the batch scheduling system, either as interactive or unattended jobs. In either case, only once a batch job has been started can the FLUENT module be loaded with the following command:

module load fluent

Additionally, you can use the following command to see the other FLUENT versions you can load on the cluster you are using:

module avail

Batch Usage

Sample Usage (interactive execution)

Using the FLUENT GUI interactivly can be done with the following steps:

  1. Ensure that your SSH client software has X11 forwarding enabled
  2. Connect to either the Oakley or Glenn system
  3. Request an interactive job. The command below will request a single-core, one hour job. Modify as per your own needs:
    qsub -I -X -l walltime=1:00:00 -l software=fluent+1
  4. Once the interactive job has started, run the following commands to setup and start the FLUENT GUI:

    module load fluent

Sample Batch Script (serial execution using 1 base token)

Running FLUENT for five-hours on an input file "run.input" on either Glenn or Oakley:

#PBS -N serial_fluent
#PBS -l walltime=5:00:00 
#PBS -l nodes=1:ppn=1
#PBS -l software=fluent+1
#PBS -j oe
# The following lines set up the FLUENT environment
module load fluent
# Move to the directory where the job was submitted from
# You could also 'cd' directly to your working directory
# Copy files to $TMPDIR and move there to execute the program
cp test_input_file.cas test_input_file.dat run.input $TMPDIR
# Run fluent
fluent 3d -g < run.input  
# Where the file 'run.input' contains the commands you would normally
# type in at the Fluent command prompt.
# Finally, copy files back to your home directory
cp *   $PBS_O_WORKDIR  

As an example, your run.input file might contain:

file/read-case-date test_input_file.cas 
solve/iterate 100
file/write-case-data test_result.cas
file/confirm-overwrite yes    


Sample Batch Script (parallel execution using HPC token)

FLUENT can be run in parallel, but it is very important that you read the documentation in the FLUENT Manual on the details of how this works. You can find the Fluent manuals on-line by following the "Further Reading" link at the bottom of this page, or clicking the "Manuals" link in the left panel of any of the software pages.

In addition to requesting the FLUENT base license token (-l software=fluent+1), you need to request copies of the ansyspar license, i.e., HPC tokens. However the scheduler cannot handle two "software" flags simultaneously, so the syntax changes. The new option is -W x=GRES:fluent+1%ansyspar+[n], where [n] is equal to the number of cores you requested minus 4.

Parallel jobs have to be submitted on Glenn via the batch system. An example of the batch script follows:

#PBS -N parallel_fluent   
#PBS -l walltime=1:00:00   
#PBS -l nodes=2:ppn=8
#PBS -j oe
#PBS -W x=GRES:fluent+1%ansyspar+12
#PBS -S /bin/bash
set echo on   
# The following lines set up the FLUENT environment   
module load fluent
# Move to the directory where the job was submitted from and   
# create the config file for socket communication library   
# Create list of nodes to launch job on   
rm -f pnodes   
cat  $PBS_NODEFILE | sort > pnodes   
export ncpus=`cat pnodes | wc -l`   
#   Run fluent   
fluent 3d -t$ncpus -pinfiniband.ofed -cnf=pnodes -g < run.input 

Further Reading

See Also

  • The FLUENT users ARMSTRONG group