Ansys Fluent/Aero/Icing Help

Ansys Fluent is the industry-leading fluid simulation software known for its advanced physics modeling capabilities and industry leading accuracy.

Running

To use ANSYS Fluent on Comet, please read the main ANSYS guide first.

Fluent tools

A number of tools are included in the Fluent component of our ANSYS license. Those which you can directly run on Comet are listed below.

You may also want to consult:

aero

To start the Fluent Aero workspace, first launch a new X11 desktop session using our Open OnDemand service.

Once the VNC Desktop session is running, launch a the terminal application from the bottom bar:

In the terminal, enter the following commands: 

$ source /nobackup/shared/containers/ansys.2025r2.sh
$ container.run bash
> aero

The Fluent Aero workspace application will open:

Functionality, the Aero workspace works the same as the main Fluent application.

fluent

ANSYS Fluent can be run in either batch mode for long, complex compute jobs, or interactively via the graphical application running on Open OnDemand. Both approaches are covered below.

Sample batch job - Single Node

This example requires testing

Running Fluent on a single node (aka a server) is the easiest method, but you are limited by the resources available on that single node (maximum of 256 cores and 1.5TB of RAM).

The example below allocates:

  • A single node
  • 32 parallel Fluent tasks, each with one CPU core (total 32 cores)
  • 128GB RAM in total
  • 8 hours of runtime
  • Uses a Slurm partition named 'default_free'

Adjust the values as needed. 

#!/bin/bash
#SBATCH --nodes=1
#SBATCH --ntasks-per-node=32
#SBATCH --cpus-per-task=1
#SBATCH --mem=128G
#SBATCH --time=08:00:00
#SBATCH --partition=default_free
 
source /nobackup/shared/containers/ansys.2025r2.sh
container.run fluent 2d -i myfluentjob.jou -gu -t $SLURM_NTASKS -driver null

Submit the job as sbatch fluent_single.sh

Sample batch job - Multi Node

This example requires testing

Multi-node Fluent jobs can take advantage of more resources simultaneously, but the script is a little more complex.

The example below allocates:

  • 4 nodes
  • 4 parallel Fluent tasks per node, each with 8 cores (32 per node), for a total of 16 Fluent tasks and 128 CPU cores (4 nodes x 4 tasks x 8 cores)
  • 64GB RAM per node, for a total of 256GB RAM (4 nodes x 64GB per node)
  • 8 hours of runtime
  • Uses a Slurm partition named 'default_free'

Adjust the values as needed. 

#!/bin/bash
#SBATCH --chdir=/path_to/your_ansys/working_directory/
#SBATCH --nodes=4
#SBATCH --ntasks-per-node=4
#SBATCH --cpus-per-task=8
#SBATCH --mem=64G
#SBATCH --time=08:00:00
#SBATCH --partition=default_free

HOSTNAMES=`scontrol show hostnames $SLURM_JOB_NODELIST`
echo "Job will run on:
$HOSTNAMES"
 
source /nobackup/shared/containers/ansys.2025r2.sh
 
# Now run ansys....
# -i : the name of your input file
# -gu and -driver null : to disable the graphical user interface

# Running on normal nodes (not low-latency)
srun container.run fluent 3ddp -g -nm -np ${SLURM_NTASKS} -nt ${SLURM_CPUS_PER_TASK} -slurm -pdefault -mpi=intel -platform=intel -i MY_PROJECT.JOU

# If running on low-latency nodes (uses infiniband inter-process communication)
#srun container.run fluent 3ddp -g -nm -np ${SLURM_NTASKS} -nt ${SLURM_CPUS_PER_TASK} -slurm -pinfiniband -mpi=intel -platform=intel -i MY_PROJECT.JOU

Submit the job as sbatch fluent_multi.sh

Note: Multi node example taken from https://innovationspace.ansys.com/forum/forums/topic/multiple-nodes-using-fluent-on-hpc-under-slurm/ Further examples may be found at https://docs.hpc.shef.ac.uk/en/latest/stanage/software/apps/ansys/fluent.html

You may need to do some performance profiling to understand whether it is better to have more tasks with fewer cpu cores per task, or fewer tasks with more cpu cores per task, e.g:

  • –ntasks-per-node=4 and –cpus-per-task=8

or…

  • –ntasks-per-node=8 and –cpus-per-task=4

This represents the same number of cores, but presented via a different mix of tasks. Some experimentation may be needed in order to find the most optimal balance of task quantity and task size.

Example graphical job

To start the graphical Fluent tool, first launch a new X11 desktop session using our Open OnDemand service.

Once the VNC Desktop session is running, launch a the terminal application from the bottom bar:

In the terminal, enter the following commands: 

$ source /nobackup/shared/containers/ansys.2025r2.sh
$ container.run bash
> fluent

The Fluent Launcher window opens:

Start a new project - make the following settings changes:

  • Parallel Settings → Shared Memory on local machine
  • Scheduler → None

If loading an existing project:

  • Home → Solution → Read → Case → Select your input data

Now press the Start button, the main Fluent application opens, either with a blank window:

… or your existing project if you chose to load one:

Testing Fluent

A copy of an interactive Fluent job is kindly provided by one of our postgraduate researchers, below:

To use this example to test Fluent, copy the .tgz to your home directory, extract it (tar -zxf fluent_example.tar.gz) and then follow these steps:

Option 1

  • Start the fluent launcher as described above
  • In the launcher window navigate to Home → Solution → Read → Case → and select the file animation/pulse_pipe_fluid_vol_transient_exp.cas.h5 from your home directory
  • Click Start in the launcher window, the Fluent application starts
  • In the outline view on the left panel of the Fluent application window navigate to Case View → Solution → then right click Initialization and choose Initialize
  • In the outline view on the left panel of the Fluent application window navigate to Case View → Solution → Calculation Activities → then right click Run Calculations and choose Calculate
  • Once solution is completed choose the File menu then → Write → Case & Data

Option 2

  • In the top menu choose the File menu then → Read → Journal → and choose animation/solve0.jou from your home directory

icing

To start the Fluent Icing workspace, first launch a new X11 desktop session using our Open OnDemand service.

Once the VNC Desktop session is running, launch a the terminal application from the bottom bar:

In the terminal, enter the following commands: 

$ source /nobackup/shared/containers/ansys.2025r2.sh
$ container.run bash
> icing

The Fluent Icing workspace application will open:

Functionality, the Icing workspace works the same as the main Fluent application.

post_analysis

To start the post_analysis tool, first launch a new X11 desktop session using our Open OnDemand service.

Once the VNC Desktop session is running, launch a the terminal application from the bottom bar:

In the terminal, enter the following commands: 

$ source /nobackup/shared/containers/ansys.2025r2.sh
$ container.run bash
> post_analysis

The post_analysis application interface will open:

udil2udil

The udil2udil tool does not need to be run in a graphical session and can be used from either a command line or desktop environment. 

$ source /nobackup/shared/containers/ansys.2025r2.sh
$ container.run udil2udil -h
udil2udil
Usage: udil2udil [-v] [-h] infile outfile
Options:
  -h              Display this information
  -fps [fps]      Change the fps for the output movie
  -options [opts] Change the writer options for the output movie
  -v              Enable verbose mode

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