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ANSYS-Fluent (CFD)

Module

Check available versions of Ansys:

module avail 2>&1 | grep -i Ansys

Load the correct version of Ansys, e.g.,

module load *your preferred module*

available modules on VSC-4:

  • ANSYS/2019R3
  • ANSYS/2020R2
  • ANSYS/2021R1

General Workflow

Pre- and postprocessing locally & remote computation on VSC

The subsequent figure shows an overview of the general workflow if you use Fluent on your local machine for pre- and postprocessing and the cluster for solving your case, respectively.
For this workflow a graphical connection isn't necessary.

All files needed for this testcase are provided here: fluent_testcase.zip

Input file

Create a journal file (fluent.jou) which is written in a dialect of Lisp called Scheme. This file may be very short, i.e., instructing the code to be read, run and written. However, it may contain up to every single instruction of a case file executed during the run. You always have the choice between writing a certain command in the journal file or in the graphical user interface (GUI).

A basic form of the journal file reads:

# -----------------------------------------------------------
# SAMPLE JOURNAL FILE
#
# read case file (*.cas.gz) that had previously been prepared
file/read-case "tubench1p4b.cas.gz"
file/autosave/data-frequency 10
solve/init/initialize-flow
solve/iterate 500
file/write-data "tubench1p4b.dat.gz"
exit yes

The autosave/data-frequency setting will save a *.dat file every 10 iterations, the flow field is initialised to zero and then the iteration is started.

Preferably do these settings in the GUI, as shown here for the autosave frequency in the subsequent graphic.

Keep in mind to set the appropriate path for the cluster. Here the files will be saved in the same directory as the journal file is located. It could be better for the sake of clarity to create an additional directory for this backupfiles, i.e.

./Autosave/*your_filename*.gz

This is a relative reference to the path, where your *.cas.gz-file is located. Also keep in mind that the folder called “Autosave” already exists before running your job.


Job script

A script for running Ansys/Fluent called fluent_run.sh is shown below.

#!/bin/sh
#SBATCH -J fluent
#SBATCH -N 2
#SBATCH -o job.%j.out
#SBATCH --ntasks-per-node=24
#SBATCH --threads-per-core=1
#SBATCH --time=04:00:00

module purge
module load *your preferred module*

JOURNALFILE=fluent.jou

if [ $SLURM_NNODES -eq 1 ]; then
    # Single node with shared memory
    fluent 3ddp -g -t $SLURM_NTASKS -i $JOURNALFILE > fluent.log 
else
    # Multi-node
    fluent 3ddp  \                # call fluent with 3D double precision solver
    -g \                          # run without GUI
    -slurm -t $SLURM_NTASKS \     # run via SLURM with NTASKS
    -pinfiniband \                # use Infiniband interconnect
    -mpi=openmpi \                # use IntelMPI
    -i $JOURNALFILE > fluent.log  # input file
fi

This job script allows a variable definition of desired configuration. You can manipulate the number of compute nodes very easily and the job script generates the appropriate command to start the calculation with Fluent.


License server settings

These variables are defined when loading the fluent module file:

setenv       ANSYSLI_SERVERS 2325@LICENSE.SERVER
setenv       ANSYSLMD_LICENSE_FILE 1055@LICENSE.SERVER

Submit job

sbatch fluent_run.sh

Restarting a calculation

To restart a fluent job, you can read in the latest data file:

# read case file (*.cas.gz) that had previously been prepared
file/read-case "MyCaseFile.cas.gz"
file/read-data "MyCase_-1-00050.dat.gz"   # read latest data file and continue calculation
solve/init/initialize-flow
solve/iterate 500
file/write-data "MyCase.dat.gz"
exit yes

doku/ansys.txt · Last modified: 2021/10/22 10:19 by sfrank