Ansys Fluent is a computational fluid dynamics code. There are a limited number of licenses available to the entire user group, you can view the license availability and status using the
flstat
command from any login node. The most important output of this command is the acfd_fluent_solver which is required to launch any instance of Fluent and acfd_par_proc which is the count of in-use or available Fluent parallel process licenses required to launch Fluent in parallel.
Launching Fluent in Parallel
There are sample submission scripts in the submission directory, /nfs/apps/Submission, you can use to launch Ansys Fluent. For parallel Fluent jobs you will want to use the one called srun_fluent, most of the default options can be used, the options you may want to change:
module load ansys/19.0
This loads the environment module for the version of Ansys Fluent you want to use, here Ansys 19.0 is being loaded, other versions are available, please view the modules documentation for further information using modules.
The following line launches Fluent in to Slurm.
fluent -t$SLURM_NTASKS -cnf=$HOSTSFILE -mpi=intel -pib.infinipath -ssh 3ddp
You should only change the last option, 3ddp, which is 3D Double Precision, other options are possible 2ddp, 2D Double Precision, etc,.
Exporting the Display and Starting Fluent
Once you have made the necessary changes to your submission script you need to export your DISPLAY. Typically Fluent is run in graphical mode and the DISPLAY environment tells Fluent where your DISPLAY is located. Your display will be listed in the title bar of the TurboVNC graphical interface, an example would be login06:10, the 10th display on the login06 system, export your DISPLAY using the following command from your login node
export DISPLAY="loginX:YY"
Where X is your login node number and YY is your display number. Once this is set you can submit your Fluent submission script to the queue and if there are sufficient licenses for it to start you will see Fluent spawn on your display.
You do not sbatch the Fluent jobs, instead it is recommended you use the srun command. For this example we will launch Fluent on 2 nodes, using 80 Fluent processes.
srun -N 2 ./srun_fluent
If you need to use a power of 2 for you job you can use the -tasks-per-node=32 flag.
srun --nodes=2 --ntasks-per-node=32 ./srun_fluent
This will spawn 64 fluent_mpi processes on 2 nodes instead of 80.
Launching Fluent in Serial
There are sample submission scripts in the hpcee directory in your user home directory you can use to launching Ansys Fluent. For serial Fluent jobs you will want to use the one called srun_fluent_serial, most of the default options can be used, the options you may want to change:
module load ansys/19.0
This loads the environment module for the version of Ansys Fluent you want to use, here Ansys 19.0 is being loaded, other versions are available, please view the modules documentation for further information using modules.
The following line launches Fluent in to Slurm.
fluent -t$SLURM_NTASKS -cnf=$HOSTSFILE -t1 3ddp
You should only change the last option, 3ddp, other options are possible, 2d, 2ddp, 2D Double Precision, etc,. Once you have completed your changes submit the script to the queue with the command below.
srun --nodes=1 ./srun_fluent_serial
Your job should begin shortly.
NOTE: Because of the way Fluent interprets non-interactive sessions this mode will launch Fluent on a single core but Fluent will require one processor from the Ansys Parallel license to be available in order to launch successfully.
For Ansys Fluent in true serial mode, you will need to request a single node and launch Fluent manually. This does not require a Fluent parallel license to launch, first allow Fluent to connect to your display with
xhost +
Then the following the steps below.
salloc -N 1 -p general
This command will allocate a single node in the General queue. Once you have been logged into this node you will need to export your DISPLAY. Your display will be listed in the title bar of the TurboVNC graphical interface, an example would be login06:10, the 10th display on the login06 system, export your DISPLAY using the following command from your login node
export DISPLAY="loginX:YY"
Where X is your login node number and YY is your display number. Once this is set you can use the module command to load the appropriate version of Fluent
module load ansys/19.0
Then simply launch fluent
node:~> fluent 3ddp
When complete, close Fluent and exit back to your login node, this will close the interactive session you have open currently.