Updated 2022-12-16


Run Fluent on the Cluster - Batch Mode


  • Fluent can be run in either batch mode or interactively
  • In the SBATCH script load ansys with module load ansys/2021R2. You can use module spider ansys to see what versions of julia are available.
  • In the computation part of your SBATCH script, enter the folder where you have stored the input files (using cd). If it is in the same dir you have/are submitting the SBATCH script from, you can use cd $SLURM_SUBMIT_DIR
  • To run fluent on the input files, use fluent -t x -g <inputfile> outputfile. There are additional options that will be covered later.
  • You MUST use the -t flag, and set it to the number of processors you requested (nodes=x * ppn=x)

Example SBATCH Script

#SBATCH -JfluentTest
#SBATCH -A [Account] 
#SBATCH -N1 --ntasks-per-node=8
#SBATCH -t120
#SBATCH -qinferno
#SBATCH -oReport-%j.out

module load ansys/2021R2
fluent -t8 -g <inputfile> outputfile
  • The #SBATCH directives are standard, requesting just 120 minutes of walltime and 1 node with 8 cores. More on #SBATCH directives can be found in the Using Slurm on Phoenix Guide
  • $SLURM_SUBMIT_DIR is a variable that represents the directory you submit the SBATCH script from. Make sure the julia script you want to run (in this case, test.jl) is in the same directory you put the SBATCH script.
  • fluent -t 8 -g <inputfile> outputfile runs the input file:

    • -t 8: specifies the number of processors to use. Must be set to the number you requested when you submitted the interactive job.
    • -g: tells fluent to run without gui
    • <inputfile>: journal file that contains same fluent commands as you would type interactively. Can be from previous session or created in text editor. More on input files here
    • outputfile: where anything normally printed to the screen will be stored (such as reports), along with errors

    Additional Options

    • 2d: run 2 dimenstional, single precision solver
    • 3d: run 3 dimensional, single precision solver
    • 2ddp: run 2 dimensional, double precision solver
    • 3ddp: run 3 dimensional, double precision solver
    • For mpi job, you MUST specify the number of processes using -t and the machinefile -cnf=
      • -mpi=pcmpi for smaller number of nodes
      • -mpi=intel for larger number of nodes
      • -pib for infiband

Run Fluent Interactively on Cluster


  • Running Fluent interactively is similiar to the usual workflow for an interactive program on the cluster. The workflow includes
    • Set up Interactive Desktop on Phoenix OnDemand
    • load Ansys in environment
    • Launch Fluent
    • Set number of processors
  • When the gui launches, you MUST set the number of processes to the number of cpus requested


Set up Interactive Desktop on Phoenix OnDemand

  • In order to access Phoenix OnDemand you must be connected to the GT VPN. If you do not already have the VPN set up, visit Configure the GT VPN
  • Once connected to the VPN you can access the application at Phoenix OnDemand.
  • Choose the Slurm Interactive Apps tab and select Interactive Desktop to setup and launch.
  • Setting up Interactive Desktop:
    • Charge Account: gts-<PI username> ("phx-pace-staff" works for trial. Required.)
    • Quality of Service: inferno
    • Node Type: GPU Tesla V100-16B or GPU Tesla V100-32B
    • Nodes: 1
    • Cores Per Node: 8 (Number of cores (CPUs) per node. Max: 24 cores per node.)
    • GPUs Per Node: 1
    • Memery Per Crore (GB): Leave blank if unsure. Total memory for job is: nodes × cores × memory per core
    • Number of hours: 1
  • After the preceding details are entered, clik the Launch button
  • Once the Launch Interactive Desktop is an available option, click the button to open a Phoenix OnDemand Interactive Desktop to use for Ansys

Load Ansys and Run Fluent

  • Open terminal in the Interactive Desktop by clicking top left Activities > search for terminal
  • All commands here on will be typed in the terminal
  • To see available versions of Ansys run
module spider ansys # lists available ansys versions
module load ansys/2021R2 # loads anays 2021 R2
fluent  #runs fluent


Setting CPU Number

  • Once you run the command fluent, a gui should pop which allows you to adjust parameters
  • Make sure you set num processes number to the number of cpus you requested when submitting the interactive job