How to use ANSYS Fluent on UCI's HPC

ANSYS Fluent Downloads

Use these downloads to install Fluent only

• Fluent 2025R2 - Windows

• Fluent 2025R2 - Linux

  • • Linux Documentation

• Note:  the HPC upgraded to Fluent 2025R2 May 2026.  

General Background

Get started with the campus HPC

1. Check out the HPC website.  

2. Request an account

   1. 1. Scroll down to "Get an account".

      2. Accounts are available to "anyone with a UCINetID" including undergrads.

3. Read the section how to prepare your laptop.

4. Learn how to log in.

   1. 1.  If you're off-campus, connect to UCI VPN first.

      2. This link explains how to set up MobaXterm.

         1. • Do NOT enable remote server monitoring! 

            • Verify the "remote monitoring" check box is de-selected after you log into the HPC.

              1. •  Go to Settings > Configuration > SSH > SSH Browser Settings (towards the top)

                 •  De-select "Remote Monitoring"

      3. hpc3.rcic.uci.edu   (host name)

5. Review unix primer, beginner's guide, and tutorials.

   1. 1. Go through all of their user guides

      2. Know simple linux commands such as "cd" and "ls".

6. Other Linux Learning includes:

   1. 1. Basic Linux Navigation

      2. Command Line for Beginners

      3. Teach Yourself Linux in 24 Hours

7. Learn basics of SLURM & Sbatch files:

   1. 1. UCI HPC SLURM

         1. • Be sure to read up on accounting.

      2. UCI HPC How to submit a SLURM job.

      3. SLURM Scheduler Basics-video 

         1. • Excellent video explaining SLURM basics.

8. Read HPC software and environment modules.

9. Learn to use a Linux text editor such as Pico or VI.

   1. 1. As a workaround, you can create text files with Notepad++ on your Windows computer and then upload it to your working directory on the HPC.

      2. To ensure Notepad++ files created on Windows are easily read by Linux, set the encoding to UTF-8 and use Unix (LF) line endings. 

         1. • In Notepad++, go to Encoding > Convert to UTF-8

            • Then Edit > EOL Conversion > Unix (LF) Format. 

              1. • This prevents character encoding issues and compatibility issues with line breaks.

      3. Enable file extensions on Windows

         1. • Settings, System, Advanced, Show Extensions > On

10. Check out Nabil's course (below).

11. Learn how to run Fluent in Batch Mode

    1. 1. This explains in detail how to run Fluent in Batch Mode

       2. For high-performance computing:

          1. • Specify the solver dimension with 3d (or 2d)

             • Run Fluent without graphics or the GUI using -g  (always use -g on the HPC)

             • Specify the number of processors using  -t   

             • Specify the journal file with -i 

               1. • For example:   fluent 3d -g -t4 -i input.jou > output.txt  

                  • This command starts Fluent, runs in 3D, no gui, with 4 cores, reads input.jou as the input file, then outputs data to output.txt.

Prepare your Files

Note:  You can prepare files locally on any computer running ANSYS.

To run a Fluent batch job using SLURM, you need these three things:

1. 1. 1. SLURM batch file (.sh)

         1. 1. This is a batch submission script (to request cluster resources).

               1. • It'll have your command for running Fluent along with other parameters.

                  • Here's an example of how to create an batch file for Fluent

                  • SLURM Scheduler Basics-video

                  • Here are some batch examples.

      2.  Case file (.cas) or (.cas.h5) 

         1. 1. This contains the mesh, physics settings, and boundary conditions. You cannot create one with a simple text editor; you must generate it using the Fluent solver itself.

            2. Where to located case files:

               1. • Workbench Projects: 

                    1. Fluent case files (.cas or .cas.h5) are typically stored within the Ansys Workbench Project Directory, buried deep in .../dp0/FFF/Fluent/

                  • Standalone Fluent

                    2. 1. Saved in the directory specified in the File/Write panel, or the launch folder.

            3. This explains how to create a Fluent .cas file

            4. Sample case file based on tutorial below

      3. Job file (.jou) - This is a journal file to automate the simulation.

         1. 1. Here's an example showing how to create a journal file

            2. Recording an Ansys Fluent Journal File 

            3. Sometimes it's easier to write your own.

            4. Here are journal examples.

Run Fluent on the HPC

Quick Start:

1. Connect to VPN, login to hpc3.rcic.uci.edu

   1. 1. Select "Option 1" to use Duo.

2. Read how to list available modules

   1. 1. This command lists all available modules:  module avail

      2. This command lists available Fluent modules:   module avail fluent

3. Read how to display module information.

   1. 1. This command displays information specifically about the fluent/2025R2 module including preset environment variables:  module display fluent/2025R2

      2. Verify the license server information.

4. Read how to load modules.

   1. 1. This loads the Fluent 2025 R2 module:   module load fluent/2025R2

      2. This will show you the Fluent app location:   which fluent

         1. 1. You should see output such as:     /data/opt/apps/ansys/2025R2/v194/fluent/bin/fluent

      3. Note:  Fluent will only work in batch mode (use -g). Don't run it with a graphical X11 interface.

5. Upload files 

   1. 1. Upload the following to a folder on the HPC:

         1. 1. SLURM batch file (.sh)

            2. Case file (.cas or .cas.h5)

            3. Journal file  (.jou)

      2. To run, type:  sbatch filename.sh   (from within the same directory)

         1. 1. Example:  sbatch fluent-batch.sh

6. How to unload modules

   1. 1. module unload fluent/2025R2

Fluent Tutorial

Use this Fluent tutorial to create a case file

1. Geometry import from SOLIDWORKS to Fluent and COMSOL

   1. 1. This video explains how to create geometry (fluid domain) in Solidworks, import it into Design Modeler, create a mesh, and then set up a Fluent case.

      2. After you setup Fluent, you can locate case files in the workbook folder:   /dp0/FFF/Fluent

2. Here are files to support this tutorial.

   1. 1. Text file listing individual steps.

      2. Solidworks geometry

Support

Engineering IT support

• • https://helpdesk.eng.uci.edu/

ANSYS Support

• • https://innovationspace.ansys.com/forum/

Additional Resources

ANSYS Fluent Guides

ANSYS - How to run Fluent in Batch Mode

Submitting Fluent jobs to SLURM from Purdue University

Fluent Job Submission Guide from Colorado School of Mines

How to Submit an Ansys Fluent Job from Cal Poly

Nabil Khalifa HPC Presentation

A crash course in CFD analysis introducing the finite volume approach and Fluent software as an application. This is the final workshop out of a series of four. A brief introduction for using Fluent on High Performance Computing units is presented, while highlighting how to deal with Fluent through the Text User Interface (TUI).

Nabil Khalifa's Crash Course in CFD

• Nabil's video playlist

• Here's the presentation slides

• Nabil's Batch File for running Fluent

Using queues with SSH,  X2GO, ANSYS

NOTE:  Some of this is out of date since the HPC switched to SLURM

1)      First type ‘q’ (Private queues specify here ‘queue name’)

2)      qrsh –q ‘queue name’ –pe openmp  ‘# of cores’ (allows you to reserve cores on a queue)

a.       qrsh – q ‘queue name’ –pe mpi  ‘# of cores’ (WARNING: always tries to take all cores no matter #of cores you type. If max cores not typed it will error out)

3)      qstat | grep ‘queue name’ (Find out who is using a queue via username)

4)      module load ansys

•  For more information see software tutorials and using modules

5)      fluent  

• This assumes you want to use Fluent

6)      qstat –u ‘username’ (see job number and etc.)

7)      qdel ‘job number’ (make sure your job is deleted when done so others can access)

8)      exit