ANSYS Fluent

ANSYS Fluent is a computational fluid dynamics (CFD) tool. Fluent includes well-validated physical modelling capabilities to deliver fast, accurate results across the widest range of CFD and multi-physics applications.

Using ANSYS Fluent on Cirrus

ANSYS Fluent on Cirrus is only available to researchers who bring their own licence. Other users cannot access the version centrally-installed on Cirrus.

If you have any questions regarding ANSYS Fluent on Cirrus please contact the Cirrus Helpdesk.

Running parallel ANSYS Fluent jobs

The following batch file starts Fluent in a command line mode (no GUI) and starts the Fluent batch file “inputfile”. One parameter that requires particular attention is “-t504”. In this example 14 Cirrus nodes (14 * 72 = 1008 cores) are allocated; where half of the 1008 cores are physical and the other half are virtual. To run fluent optimally on Cirrus, only the physical cores should be employed. As such, fluent’s -t flag should reflect the number of physical cores: in this example, “-t504” is employed.


# Slurm job options (name, compute nodes, job time)
#SBATCH --job-name=ANSYS_test
#SBATCH --time=0:20:0
#SBATCH --exclusive
#SBATCH --nodes=4
#SBATCH --tasks-per-node=36
#SBATCH --cpus-per-task=1

# Replace [budget code] below with your budget code (e.g. t01)
#SBATCH --account=[budget code]
# Replace [partition name] below with your partition name (e.g. standard,gpu)
#SBATCH --partition=[partition name]
# Replace [qos name] below with your qos name (e.g. standard,long,gpu)
#SBATCH --qos=[qos name]

# Set the number of threads to 1
#   This prevents any threaded system libraries from automatically
#   using threading.

export HOME=${HOME/home/work}

scontrol show hostnames $SLURM_NODELIST > ~/

# Launch the parallel job
./fluent 3ddp -g -i inputfile.fl \
  -pinfiniband -alnamd64 -t504 -pib    \
  -cnf=~/      \
  -ssh  >& outputfile.txt

Below is the Fluent “inputfile.fl” batch script. Anything that starts with a “;” is a comment. This script does the following:

  • Starts a transcript (i.e. Fluent output is redirected to a file [transcript_output_01.txt])
  • Reads a case file [a case file in Fluent is a model]
  • Reads a data file [a data file in Fluent is the current state of a simulation (i.e. after X iterations)]
  • Prints latency and bandwidth statistics
  • Prints and resets timers
  • Run 50 iterations of the simulation
  • Prints and resets timers
  • Save the data file (so that you can continue the simulation)
  • Stops the transcript
  • Exits Fluent

Actual Fluent script (“inputfile.fl”):

Replace [Your Path To ] before running

; Start transcript
/file/start-transcript [Your Path To ]/transcript_output_01.txt
; Read case file
rc [Your Path To ]/200M-CFD-Benchmark.cas
; Read data file
/file/read-data [Your Path To ]/200M-CFD-Benchmark-500.dat
; Print statistics
; Calculate 50 iterations
it 50
; Print statistics
; Write data file
wd [Your Path To ]/200M-CFD-Benchmark-500-new.dat
; Stop transcript
; Exit Fluent