Ansys Fluent, CFX

Versions

Currently installed versions include: 2022r2, 2023r1, 2024r2 In the future, autumn releases will be installed. The file paths are the following for the versions: /opt/software/packages/ansys/<version>

Licensing

A license is required to use Ansys Fluent. Kommondor has a license server with hundreds of licenses. With the recent licensing change, a simulation might use two kinds of licenses. There’s a base license called cfd_base, which covers up to 4 cores. Above 4 cores, anshpc licenses are used. One license covers one additional core. For example a simulation using 16 cores would use a base fluid license and 12 HPC licenses for 4+12*1=16 cores in total. License availability can be checked using the license manager:

/opt/software/packages/ansys/2024r2/v242/licensingclient/linx64/lmutil lmstat -a -c 1055@license.komondor.hpc.einfra.hu | grep -e "anshpc" -e "cfd_base"

Creating Journal file in Ansys Fluent

  1. File -> Write -> Start Journal

  2. Apply the necessary settings using the Text User Interface, run a few iterations of the simulation than save the results.

  3. File -> Write -> Stop Journal

  4. You can edit and modify the created Journal file using a text editor (eg. number of iterations, save location, etc.)

Alternative method:

A journal file is just a text file disguised with a .jou extension containing the commands. So, writing a journal file from scratch is possible, and it can be more flexible than the GUI method mentioned above. The text file needs to be saved with the .jou extension. A simple example can be seen below:

;changing working directory
sync-chdir <Path to working directory>

;Reading in the case file
/rc "<Path to case file>"
; an alternative form of this is "/file/read-case fullcase.cas.gz"

;initialising the system
/solve/init/init

;Setting the number of time-steps (first number) and the max
;number of iterations per step (second number)
/solve/dual-time-iterate 1000 10

;Outputting solver performance data upon completion of the simulation
/parallel timer usage

;Writing the final case file (overwriting if required)
/wc "<Path for case file>"
yes

;Writing the final data file (overwriting if required)
/wd "<Path for data file>"
yes
; an alternative form of this is "/file/write-data output_results.data ok"

/exit ok

For transient simulations with adaptive time steps or more complex setups, the commands have to be recorded in the GUI. Steady-state simulations can be run with the following command with the number of maximum iterations specified:

solve/iterate 100

Other useful commands:

Creating a SLURM script

#!/bin/bash
#SBATCH --job-name=<job-name>
#SBATCH --output=%j.out
#SBATCH --error=%j.err
#SBATCH --partition=cpu
#SBATCH --nodes=1
#SBATCH --ntasks-per-node=8
#SBATCH --time=00:10:00
#SBATCH --account=<project-name>

### NOTICE. DO NOT use flag "--cpus-per-task= "
### It will break job setting, so no MPI/OpenMP job

export SLURM_MPI_TYPE=pmi2
export OMP_NUM_THREADS=1
export SSH_SPAWN=0
export I_MPI_OFI_LIBRARY_INTERNAL=0
export INTELMPI_ROOT=/opt/software/packages/intel/mpi/2021.9.0/
export SLURM_CPU_BIND=none

if [ $SLURM_JOB_NUM_NODES -eq 1 ]
then
export I_MPI_FABRICS=shm
fi

rm -rf fluentHostfile
FLUENTNODES="$(scontrol show hostnames)"
echo $FLUENTNODES > fluentHostfile

export ANSYSLMD_LICENSE_FILE=1056@license.komondor.hpc.einfra.hu

/opt/software/packages/ansys/2023r1/ansys_inc/v231/fluent/bin/fluent 3ddp -g -t $SLURM_NTASKS -mpi=intel -mpiopt="-genv FI_PROVIDER cxi -genv I_MPI_PIN 1 -genv I_MPI_PIN_CELL core -genv FI_PROVIDER_PATH /opt/cray/libfabric/1.15.2.0/lib64/"  -i  <journal-file> -cnf=fluentHostfile -scheduler_tight_coupling -pcheck=0

Change the parts marked as <$variable> according to your own preferences. If it is necessary, change the parameters below:

2d – 2D, single-precison solver
3d – 3D, single-precision solver
2ddp – 2D, double-precision solver
3ddp – 3D, double-precison solver
-g – run without GUI and graphics
-i <journal> - reading in a Journal file

Other commands: Ansys Fluent User’s Guide (2023/R2) / 4.1.5. Command Line Startup Options

Note

You can issue TUI commands directly after opening Fluent. In this case, the Journal file is unnecessary.

Running a job

  1. Upload the necessary files to the directory you want to use (eg. using WinSCP).

  2. Login to the server via SSH.

  3. Use the following commands:

cd <working_directory>
sbatch <script_name>.sbatch

  1. You can monitor your submitted jobs with the following command:

squeue -u <user-name>

CFX

Unlike Fluent, CFX works with multiple executables for different tasks. So running a simulation is simpler, and does not require a journal file. A simulation prepared in a definiton file can be run with the following command:

cfx5solve -batch -def <path to .def file> -chdir <path to working directory on scratch> -parallel -part <number of cores> -start-method "Open MPI Local Parallel" -par-dist <hostfile>

The -chdir option is required, otherwise it will not work.

Creating a SLURM script

#!/bin/bash
#SBATCH --job-name=<job-name>
#SBATCH --output=%j.out
#SBATCH --error=%j.err
#SBATCH --partition=cpu
#SBATCH --nodes=1
#SBATCH --ntasks-per-node=16
#SBATCH --time=10:10:00
#SBATCH --account=<project-name>


### NOTICE. DO NOT use flag "--cpus-per-task= "
### It will break job setting, so no MPI/OpenMP job

export SLURM_MPI_TYPE=pmi2
export OMP_NUM_THREADS=1
export SSH_SPAWN=0
export I_MPI_OFI_LIBRARY_INTERNAL=0
export INTELMPI_ROOT=/opt/software/packages/intel/mpi/2021.9.0/
export SLURM_CPU_BIND=none

if [ $SLURM_JOB_NUM_NODES -eq 1 ]
then
export I_MPI_FABRICS=shm
fi

rm -rf cfxHostfile_2
CFXNODES="$(scontrol show hostnames)"
echo "${CFXNODES}*$SLURM_NTASKS," > cfxHostfile_2


export ANSYSLMD_LICENSE_FILE=1056@license.komondor.hpc.einfra.hu

/opt/software/packages/ansys/<version>/ansys_inc/<version>/CFX/bin/cfx5solve -batch -def <Path to .def file> -chdir <Path to working directory> -parallel -part $SLURM_NTASKS  -start-method "Open MPI Local Parallel" -par-dist cfxHostfile_2

The results can be exported using cfx5export, using the -help flag the available formats and their options can be listed.

/opt/software/packages/ansys/<version>/ansys_inc/<version>/CFX/bin/cfx5export -help