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ICHEC Software

Information about software packages installed on the ICHEC systems.

ANSYS FLUENT

Versions Installed

Stokes: 12.1 / 14.0

Stoney: 12.1 / 14.0

Description

ANSYS FLUENT is a general purpose commercial package for Computational Fluid Dynamics (CFD). It's modelling capabilities include acoustics, heat transfer, reacting flow, multiphase flow and dynamic mesh motion.

License

In order to use Fluent, the user must contact the Helpdesk and request that they be added to the ansys group.

For ANSYS products of version 12.0 and higher, new users have to specifically request the licensing system to use an academic license as opposed to a commercial license (the default). The most convenient way do this is to download the following license configuration file and copy it to ~/.ansys/v121/licensing/ (you will need to create this directory if it doesn't exist): license.preferences.xml

25 seats and 128 parallel tokens are currently available for ANSYS products.

Benchmarks

N/A.

Job Submission Example

Like other jobs on ICHEC systems, Fluent jobs must be submitted using a PBS script. The PBS script should launch the Fluent executable with the Graphical User Interface (GUI) disabled. This can be achieved by specifying the -g argument on the command line. When the GUI is disabled, Fluent commands can be issued using the Fluent Text User Interface (TUI). A series of TUI commands can be saved to a text file, which can subsequently read by the Fluent solver using the -i command line argument. The following is a minimal example PBS script for running a steady-state 3D Fluent job on 24 cores of the Stokes system for a maximum walltime of 5 hours (the Fluent case file is called "example.cas.gz"):

#!/bin/bash
#PBS -l nodes=2:ppn=12
#
#For Stoney, you must use ppn=8
#e.g. for a 16-core job:
##PBS -l nodes=2:ppn=8
#
#PBS -l walltime=5:00:00
#PBS -N myJobName
#PBS -A myProjectName

module load ansys
# default vs is 12.1 to load vs 14.0 use 'module load ansys/14.0'
cd $PBS_O_WORKDIR

#Run the fluent executable:
fluent 3ddp -g -ssh -pinfiniband -cnf=$PBS_NODEFILE < FluentCommandFile.txt >myJob.log 2>&1

The following is a summary of Fluent command line parameters used in the above PBS script:

  • 3ddp: Run a 3D simulation in double precision (remove dp for single precision).
  • -g: Run Fluent without the GUI
  • -ssh: Use ssh to login to the available nodes (rsh is the default, which is not supported)
  • -pinfiniband: Use infiniband interconnect
  • -cnf=$PBS_NODEFILE: Provides the Fluent solver with the list of nodes allocated to the PBS job
  • < FluentCommandFile.txt: Read Fluent commands from FluentCommandFile.txt . This is a plain text file containing the commands that will be executed by the Fluent solver.
  • >myJob.log 2>&1: Redirect the Fluent output information to "myJob.log"

For this example, FluentCommandFile.txt contains the following Fluent commands (comments in this file begin with a semicolon (;)):

; Read the Fluent case file
/file/read-case/example.cas.gz
; Initialise the flow field
/solve/initialize/initialize-flow
; Run the solver for 200 iterations
/solve/iterate 200
; Write the results to a data file
/file/write-data example.dat
; Exit Fluent
exit
yes

This job can be submitted using the command

qsub scriptname.pbs

where scriptname.pbs is the filename of the sample PBS script

Checking License Availability in PBS

On Stokes and Stoney users can specify the number of tokens required per job so that jobs will only be started if there are enough tokens available. This can be done by including the following lines in the PBS script.

#PBS -W x=GRES:aa_r_hpc+M

where M is the number of parallel tokens required for a job. The base Fluent token provides four parallel tokens so a job requires the number of cores minus four. For example, a two node job requires 24 - 4 = 20 parallel tokens.

Compatibility with TaskFarming

Taskfarming is a utility provided by ICHEC to allow for multiple parallel jobs to be executed within one batch process. It can be used in conjunction with Fluent allowing for high throughput of simulations. Users interested in expoiting this should contact the helpdesk for assistance.

Additional Notes

Further information can be obtained in the Fluent documentation and at www.ansys.com.

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