ANSYS Installations on Tetralith & Sigma

Official homepage: https://www.ansys.com

In order to use ANSYS software, you need a licence. Either you belong to a LiU research group that has a license for this software, or you have to provide your own licence.

ANSYS Documentation

ANSYS provides a customer portal: https://support.ansys.com
We recommend the customer portal to search for documentation, examples, etc. If you have a licence for an ANSYS product, e.g. Fluent or CFX, you probably also have access to the customer portal.

Installed ANSYS Versions

Version NSC Module Installation Path
2020R2 ansys/2020R2-nsc1 /software/sse/manual/ansys/2020R2/nsc1/v202/
2020R1 ansys/2020R1-nsc1 /software/sse/manual/ansys/2020R1/nsc1/v201/
2019R1 ansys/2019R1-nsc1 /software/sse/manual/ansys/2019R1/nsc1/v193/
19.0 ansys/19.0-nsc1 /software/sse/manual/ansys/19.0/nsc1/v190/
18.2 ansys/18.2-nsc1 /software/sse/manual/ansys/18.2/nsc1/v182/
17.2 ansys/17.2-nsc1 /software/sse/manual/ansys/17.2/nsc1/v172/

Note: From 2019 on, ANSYS changed the naming of the versions. We apply the official naming convention, e.g. version 2019R1.

How to run

Load the ANSYS module corresponding to the version you want to use, e.g

module load ansys/2019R1-nsc1

This gives you access to all ANSYS software, including Fluent, CFX, ANSYS workbench etc.

How to start the ANSYS workbench interface

ANSYS provides many different software packages. The ANSYS Workbench provides a general graphical interface to access all available software components. ANSYS Workbench can be started by the command:

runwb2

To use graphical hardware acceleration on a login node, we recommend to use vglrun:

vglrun runwb2

Settings for Parallel Tasks, Intel MPI and Omni-Path Network

Number of Parallel tasks

ANSYS Fluent version before 19.0
Until ANSYS version 19, one has to specify a machine file using the option -cnf=<machinefile>

ANSYS Fluent version after 19.0
From ANSYS version 19 onward, the option -cnf is not used anymore. Instead, one has to specify the number of parallel tasks using the option -t<number of tasks>, e.g. -t32 to use 32 parallel tasks.
In a batch script, it is inconvenient to manually specify the number of tasks, since this information is already specified by the number of nodes/cores, according to the SLURM options (#SBATCH -N, #SBATCH -n).

The number of parallel tasks can be determined from the SLURM options as following:

tasks=$(hostlist --repeat-slurm-tasks="$SLURM_TASKS_PER_NODE" "$SLURM_NODELIST" -e | wc -l)

fluent -t$tasks ...

Intel MPI and Omni-Path

Tetralith nodes are interconnected using Intel Omni-Path network. Our previous system Triolith used Infiniband. Therefore, the correct settings for the interconnect fabric differ between Tetralith and Triolith. If you manually provide the employed MPI and interconnect fabric for your ANSYS application, you might have to adjust them accordingly.

Example for Fluent using Intel MPI and Omni-Path:

-mpi="intel" -pib.infinipath

When using the NSC Fluent wrapper, you do not have to specify the options -mpi,-pib,-t. The wrapper takes care about the correct settings. The description is only intended for completeness and if you do not use our wrapper. The information is useful, when you want to run Fluent on other systems as well.

Fluent Wrapper

Fluent should be started using the NSC wrapper. The NSC wrapper uses the preferred Intel MPI library and the correct settings for Omni-Path fabric, so you do not have to take care about it. That means, you should not add any option -mpi or -pib, since these are added automatically. If you do not use the NSC wrapper, you have to adjust your mpi and interconnect settings as decribed in the previous section. Further, you do not need to specify the number of tasks (option -t). This is automatically done within the wrapper as well.

We provide the environment variable

$NSC_FLUENT_WRAPPER

which is available, after loading the ANSYS module.

Alternatively, you can use the full path:

Fluent 2020R2:  /software/sse/manual/ansys/2020R2/nsc1/fluent_nsc.sh
Fluent 2020R1:  /software/sse/manual/ansys/2020R1/nsc1/fluent_nsc.sh
Fluent 2019R1:  /software/sse/manual/ansys/2019R1/nsc1/fluent_nsc.sh
Fluent 19.0:    /software/sse/manual/ansys/19.0/nsc1/fluent_nsc.sh
Fluent 18.2:    /software/sse/manual/ansys/18.2/nsc1/fluent_nsc.sh
Fluent 17.2:    /software/sse/manual/ansys/17.2/nsc1/fluent_nsc.sh

Note: The NSC_FLUENT_WRAPPER can only be used on a compute node, but not on a login node.

How to run Fluent Interactively

When running the Fluent/ANSYS GUI, NSC recommends using ThinLinc to access Tetralith.
For more information on how to use ThinLinc, please see: Running graphical applications using ThinLinc ThinLinc is avaible for all platforms (Macintosh, Windows, Linux).

Load the ANSYS version that you would like tu use, e.g.

module load ansys/2019R1-nsc1

Start Fluent interactively, using the NSC wrapper script:

$NSC_FLUENT_WRAPPER

Meshing in Fluent

Fluent has an integrated module to create meshes. It can be accessed via the Fluent Launcher, when starting Fluent interactively. In the GUI of the Fluent Laucher, you have to choose: Options -> Meshing Mode. In the section "Processing Options" you have to choose "Parallel (Local Machine)" and adjust the number of Meshing Processes not to be 0. Do not choose "Serial", even if you are only using one core. The "Serial" mode does not work on Tetralith.

Example Batch Script

To run Fluent in batch mode, it has to be submitted via a SLURM batch script, as the following example illustrates:

#!/bin/bash
#SBATCH -n 64
#SBATCH -t 00:20:00
#SBATCH -J jobname
#SBATCH -A SNIC-xxx-yyy

module load ansys/2019R1-nsc1

JOURNAL=your_fluent_journal_file.scm

$NSC_FLUENT_WRAPPER -g 3ddp -i $JOURNAL

Submit the script via the command: sbatch <script file>


You have to adjust the batch script as follows:

  1. Specify the number of cores via the option #SBATCH -n<cores>

  2. Specify the required time #SBATCH -t <time>

  3. Change the jobname #SBATCH -J <job name>

  4. Specify your account name #SBATCH -A <account name>

  5. Adjust the name of your JOURNAL file (testcase)

  6. The option "-g" starts Fluent without a graphical interface

  7. The Option "3ddp" starts Fluent in 3D mode, using double precision


A list of available runtime options for Fluent can be accessed via

$NSC_FLUENT_WRAPPER -help

Common Fluent Options

The following options are commonly used as arguments, when starting Fluent in a batch script

Option Dscription
-g start Fluent without graphical interface. Use this option in batch scripts.
-i <JOURNAL> read the specified Fluent Journal File
2ddp 2D simulation, using double precision
3ddp 3D simulation, using double precision
2d 2D simulation, using single precision
3d 3D simulation, using single precision

Potential Problems

  1. When running a simulation via the GUI or a batch script, you should choose the same floating point precision, namely single or double precision. In the batch script, the option "3ddp" starts a 3D calculation with double precision mode. In the Fluent Laucher GUI, you find the Option "Double Precision", which may not be selected by default. This may potentially lead to a different behaviour of your solution process and accuracy when you compute interactively and in batch mode, if you do not choose the same precision.

  2. In the Fluent GUI, there are options to check the mesh quality. Under the menu item Mesh , you find the menu items Check and Check Quality to ensure that the mesh quality is okay. An insufficient mesh quality may lead to poor results, slow convergence or even a breakdown of the solution process.

  3. Paraview and Ensight Gold Format. In version ANSYS 2019R1, it seems that the export to the ensight gold format has changed. Fluent adds a new section "SCRIPTS" and some metadata information to the ensight gold case file. Paraview does not know these additional options and will complain about it. In this case, you have to remove these lines in the ensight gold case file.


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