Fluent

Category

Engineering, Fluid dynamics

Description

ANSYS Fluent is a fluid dynamics (CFD) software tool that includes physical modeling capabilities across a wide range of CFD and multiphysics applications. It can be used to model flow, turbulence, heat transfer, and reactions for industrial applications.

Available versions (Euler, old software stack)

Legacy versions	Supported versions	New versions
14.5, 15.0	16.2, 17.0	18.0, 18.2

Please note that this page refers to installations from the old software stack. There are two software stacks on Euler. Newer versions of software are found in the new software stack.

Environment modules (Euler, old software stack)

Version	Module load command	Additional modules loaded automatically
14.5	module load legacy fluent/14.5	centos_cruft/6
15.0	module load legacy fluent/15.0	centos_cruft/6
16.2	module load fluent/16.2	legacy centos_cruft/6
17.0	module load fluent/17.0	legacy centos_cruft/6
18.0	module load new fluent/18.0
18.2	module load new fluent/18.2
19.5	module load new fluent/19.5

Please note that this page refers to installations from the old software stack. There are two software stacks on Euler. Newer versions of software are found in the new software stack.

How to submit a job

For submitting a fluent job, you need to create a journal file, which contains the commands that fluent should run. You can submit a fluent job for the journal file my_journal_file.jou with the following command.

sbatch [Slurm options] --wrap="fluent [fluent options] -i my_journal_file.jou"

Here you need to replace [LSF options] with LSF parameters for the resource requirements of the job. Please find a documentation about the parameters of bsub on the wiki page about the batch system. Note that for parallel jobs, it is sufficient to use the -n option of bsub. The batch system will automatically set the fluent parameter for specifying the number of cores, based on the value that you specify for -n. Please find below some description for the command line parameters, the are in the submission command specified as [fluent options].

Parameter	Description
-cc	Use the classic color scheme
-env	Show environment variables
-mesher	Start Ansys Fluent in meshing mode
-nm	Don't display mesh after reading it
-post	Start the Ansys Fluent post-processing-only executable
-rx	Specify realease number

A typical Fluent job submission could look like the following:

sbatch --time=8:00:00 --mem-per-cpu=2g --tmp=2g --wrap="fluent 2d -i fluent_case.jou > output.out"

In fluent, you can choose between single and double precision solvers. The choice can be specified via the parameter that indicates if the model is two or three-dimensional. In this example command, ouput is redirected to the file output.out.

Keyword	Description
2d	two-dimensional model single precision
2ddp	two-dimensional model double precision
3d	three-dimensional model single precision
3ddp	three-dimensional model double precision

Parallel jobs

You can run parallel fluent jobs on the cluster, by specifying the number of cores through the -n option of bsub. Fluent supports distributed memory parallel mode, which allows you to run single simulations across multiple compute nodes. Using fluent, you can choose between PCMPI and Intel MPI. On our HPC clusters, we noticed a problem with the CPU affinity settings, when using PCMPI. In some cases, all MPI processes were bound to a single processor core, which lead to a slow down for those jobs (by a factor that is equal to the number of cores, that users specified for the simulation). Therefore, we strongly recommend to not change any MPI settings through command line parameters. For parallel fluent jobs, the batch system automatically sets the MPI options such that Intel MPI is used.

Example

As an example, we use a parallel fluent job, that runs on 4 cores.

[leonhard@euler02 fluent]$ ls
baseline.jou  test_mesh.msh
[leonhard@euler02 fluent]$ module load fluent/17.0
[leonhard@euler02 fluent]$ bsub -n 4 -W 1:00 -R "rusage[mem=2048,scratch=2048]" "fluent 2ddp -i baseline.jou &> test.log"    
Fluent job.
Job <26024496> is submitted to queue <normal.4h>.
[leonhard@euler02 fluent]$ bjobs
JOBID      USER        STAT  QUEUE      FROM_HOST   EXEC_HOST   JOB_NAME   SUBMIT_TIME
26024496   leonhard    PEND  normal.4h  euler02                 * test.log Aug 29 15:29
[leonhard@euler02 fluent]$ bjobs
JOBID      USER        STAT  QUEUE      FROM_HOST   EXEC_HOST   JOB_NAME   SUBMIT_TIME
26024496   leonhard    RUN   normal.4h  euler02     4*e1123     * test.log Aug 29 15:29
[leonhard@euler02 fluent]$ ls
baseline.jou  iso_htc_baseline.out  lsf.o26024496  test.log  test_mesh.msh

Since we redirected the output, the log information will be stored in the file test.log instead of lsf.o26024496.

License information

Commercial (centrally provided by IT shop)

Links

http://www.ansys.com/Products/Fluids/ANSYS-Fluent

https://www.youtube.com/user/ansysinc/videos
https://en.wikipedia.org/wiki/Ansys#Fluid_Dynamics