NUS staff and student can access and use ANSYS CFD software in the central HPC system. To start please register your NUS account for the HPC access. After your account is enabled in the HPC system, you can log into the system with your NUS account and password to run the software on the system. This diagram (connect to NUS-VPN if outside of campus) illustrates the steps.

Workbench is the default pre-processor of FLUENT solver. The DesignModeler is used for geometry creation and Meshing is used for mesh generation.

For post-processing, you can either use the build-in post-processor of Fluent or CFD-Post. You can also export the result to a neutral file and visualise it with EnSight, a powerful 3D visualisation software that is also available to use.

The latest version of Fluent/CFX is 2022R1. You can always check the version in the GUI of Workbench, Fluent or CFX via Help / (About…) or (Version…).

You can run the interactive Workbench, Fluent and CFD-Post graphics interface (GUI) at HPC Portal or an Xterm window of any Atlas login node. You are also recommended to run Pre-processing (Geometry creation in DesignModeler and Meshing) in a Windows computer. Check next FAQ for more.

To start Workbench, enter command “workbench &” at the command prompt. After the GUI launched, drag-drop Fluent or CFX module from the left-side Analysis Systems column into the central Project Schematic area to start a project. After this, click on Geometry to start DesignModeler and followed by Mesh to do the mesh generation.

Workbench GUI, especially for DesignModeler (DM) and Meshing, does not run well on Linux platform. So you can also download and install ANSYS Student version (free with 12 months renewable license, please Google the link for download) on your Windows computer and run Workbench DM directly for geometry creation and Meshing for mesh generation. After you create the geometry and mesh of the model, you can upload the mesh file to HPC system to continue your simulation in Fluent solver, decoupled it from Workbench.

This is a license problem and it can be fixed by changing the license preferences for Workbench.

In Workbench GUI, go to Tools / License Preferences.., and then choose “Use a separate license for each application”. After that close Workbench and start workbench again to continue the Meshing.

To access the tutorial files, you need logon to any HPC host. The Fluent tutorial files are saved in folder /app1/common/ansys/help/tutfiles_fluent/  and CFX tutorial files are saved in /app1/common/ansys/help/tutfiles_CFX/. Please copy the needed files to your own space for practice. To unzip the files, use command “unzip filename.zip”. For example:

#  cp  /app1/common/ansys/help/tutfiles_fluent/introduction.zip introduction.zip
  # unzip introduction.zip

Alternative, you can register a student access to the ANSYS Student Portal with this serial number (347798). You can find and download all the documentations and tutorial files from the Student Portal.

You can run the FLUENT/CFX solver interactively at HPC Portal or Xterm on AtlasX login nodes   for small jobs, setup and test run of big modeling cases.

For large and long hours FLUENT/CFX simulation jobs, you should submit the jobs to batch queues for batch computing. Check the FLUENT/CFX Parallel Computing part for more details and instructions.

When your FLUENT/CFX model is too huge and needs hours, days or even a couple of weeks to complete, you should submit the jobs to batch queues and run batch parallel computing FLUENT/CFX solver to speed up the simulation. Check the FLUENT/CFX Parallel Computing part for more details and instructions.

FLUENT interface includes the post-process tool. You can visualize the results from the pull down menu of “Display” and “Plot”. CFX results are post-processed in CFD-Post.

You can also use CFD-Post to visualise the Fluent result. CFD-Post comes with a better animation functions and is easy to use. To start CFD-Post, enter command “cfdpost &” at the command line prompt.

FLUENT User Define Functions (UDF) shall be written in C language. A good way to start trying of UDF is to check FLUENT documentation at UDF Manual –> Examples. You can copy and modify the example UDFs if they are relevant.

The Fluent script created on Windows/DOS may not work properly when you use the script file for the batch Fluent jobs. For example, you may notice the following Error message in the batch job std output:

Error: eval: unbound variable
Error Object: 20
Invalid integer.

Under this situation, you need to check and convert the script file from a Windows/DOS text file into a Unix/Linux text file. For example, you can do the following on a Linux command line prompt:

> file run1.txt
run1.txt: ASCII text, with CRLF line terminators

> cat -v run1.txt 
rcd test.cas.gz^M
it 500^M
... 

> dos2unix -o run1.txt
dos2unix: converting file run1.txt to UNIX format ...

> file run1.txt
run1.txt: ASCII text


> cat -v run1.txt 
rcd test.cas.gz
it 500
...

Once you convert the file into a purely “ASCII text” file using the dos2unix command, you can notice that the file format will be corrected without the “CRLF line terminators” via file command or no more “^M” at the end of each line via cat -v command. With the file format corrected, you can submit the job again and it should work fine.

When you encounter the following Error during the compilation of your UDF in Fluent:

Error: velocity.c: line 2: syntax error.

it may indicate that the UDF file format is not properly set. You can correct it with the method mentioned in the previous question.

You can use the following command to check the FLUENT/CFX license usage.

> fluent -use