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ANSYS Fluent
============
[ANSYS
Fluent](http://www.ansys.com/Products/Simulation+Technology/Fluid+Dynamics/Fluid+Dynamics+Products/ANSYS+Fluent)
software contains the broad physical modeling capabilities needed to
model flow, turbulence, heat transfer, and reactions for industrial
applications ranging from air flow over an aircraft wing to combustion
in a furnace, from bubble columns to oil platforms, from blood flow to
semiconductor manufacturing, and from clean room design to wastewater
treatment plants. Special models that give the software the ability to
model in-cylinder combustion, aeroacoustics, turbomachinery, and
multiphase systems have served to broaden its reach.
1. Common way to run Fluent over pbs file
------------------------------------------------------
To run ANSYS Fluent in batch mode you can utilize/modify the
default fluent.pbs script and execute it via the qsub command.
`
#!/bin/bash
#PBS -S /bin/bash
#PBS -l nodes=2:ppn=16
#PBS -q qprod
#PBS -N $USER-Fluent-Project
#PBS -A XX-YY-ZZ
#! Mail to user when job terminate or abort
#PBS -m ae
#!change the working directory (default is home directory)
#cd <working directory> (working directory must exists)
WORK_DIR="/scratch/$USER/work"
cd $WORK_DIR
echo Running on host `hostname`
echo Time is `date`
echo Directory is `pwd`
echo This jobs runs on the following processors:
echo `cat $PBS_NODEFILE`
#### Load ansys module so that we find the cfx5solve command
module load ansys
# Use following line to specify MPI for message-passing instead
NCORES=`wc -l $PBS_NODEFILE |awk '{print $1}'`
/ansys_inc/v145/fluent/bin/fluent 3d -t$NCORES -cnf=$PBS_NODEFILE -g -i fluent.jou
`
Header of the pbs file (above) is common and description can be find
on [this
site](../../resource-allocation-and-job-execution/job-submission-and-execution.html).
[SVS FEM](http://www.svsfem.cz) recommends to utilize
sources by keywords: nodes, ppn. These keywords allows to address
directly the number of nodes (computers) and cores (ppn) which will be
utilized in the job. Also the rest of code assumes such structure of
allocated resources.
Working directory has to be created before sending pbs job into the
queue. Input file should be in working directory or full path to input
file has to be specified. Input file has to be defined by common Fluent
journal file which is attached to the Fluent solver via parameter -i
fluent.jou
Journal file with definition of the input geometry and boundary
conditions and defined process of solution has e.g. the following
structure:
/file/read-case aircraft_2m.cas.gz
/solve/init
init
/solve/iterate
10
/file/write-case-dat aircraft_2m-solution
/exit yes
The appropriate dimension of the problem has to be set by
parameter (2d/3d).
2. Fast way to run Fluent from command line
--------------------------------------------------------
`
fluent solver_version [FLUENT_options] -i journal_file -pbs
`
This syntax will start the ANSYS FLUENT job under PBS Professional using
the qsub command in a batch manner. When
resources are available, PBS Professional will start the job and return
a job ID, usually in the form of
*job_ID.hostname*. This job ID can then be used
to query, control, or stop the job using standard PBS Professional
commands, such as qstat or
qdel. The job will be run out of the current
working directory, and all output will be written to the file
fluent.o>
*job_ID*.
3. Running Fluent via user's config file
----------------------------------------
The sample script uses a configuration file called
pbs_fluent.conf if no command line arguments
are present. This configuration file should be present in the directory
from which the jobs are submitted (which is also the directory in which
the jobs are executed). The following is an example of what the content
of pbs_fluent.conf can be:
`
input="example_small.flin"
case="Small-1.65m.cas"
fluent_args="3d -pmyrinet"
outfile="fluent_test.out"
mpp="true"
`
The following is an explanation of the parameters:
input is the name of the input
file.
case is the name of the
.cas file that the input file will utilize.
fluent_args are extra ANSYS FLUENT
arguments. As shown in the previous example, you can specify the
interconnect by using the -p interconnect
command. The available interconnects include
ethernet (the default),
myrinet, class="monospace">
infiniband, vendor,
altix>, and
crayx. The MPI is selected automatically, based
on the specified interconnect.
outfile is the name of the file to which
the standard output will be sent.
mpp="true" will tell the job script to
execute the job across multiple processors.
To run ANSYS Fluent in batch mode with user's config file you can
utilize/modify the following script and execute it via the qsub
command.
`
#!/bin/sh
#PBS -l nodes=2:ppn=4
#PBS -1 qprod
#PBS -N $USE-Fluent-Project
#PBS -A XX-YY-ZZ
cd $PBS_O_WORKDIR
#We assume that if they didn’t specify arguments then they should use the
#config file if [ "xx${input}${case}${mpp}${fluent_args}zz" = "xxzz" ]; then
if [ -f pbs_fluent.conf ]; then
. pbs_fluent.conf
else
printf "No command line arguments specified, "
printf "and no configuration file found. Exiting n"
fi
fi
#Augment the ANSYS FLUENT command line arguments case "$mpp" in
true)
#MPI job execution scenario
num_nodes=‘cat $PBS_NODEFILE | sort -u | wc -l‘
cpus=‘expr $num_nodes * $NCPUS‘
#Default arguments for mpp jobs, these should be changed to suit your
#needs.
fluent_args="-t${cpus} $fluent_args -cnf=$PBS_NODEFILE"
;;
*)
#SMP case
#Default arguments for smp jobs, should be adjusted to suit your
#needs.
fluent_args="-t$NCPUS $fluent_args"
;;
esac
#Default arguments for all jobs
fluent_args="-ssh -g -i $input $fluent_args"
echo "---------- Going to start a fluent job with the following settings:
Input: $input
Case: $case
Output: $outfile
Fluent arguments: $fluent_args"
#run the solver
/ansys_inc/v145/fluent/bin/fluent $fluent_args > $outfile
`
It runs the jobs out of the directory from which they are
submitted (PBS_O_WORKDIR).
4. Running Fluent in parralel
-----------------------------
Fluent could be run in parallel only under Academic Research license. To
do so this ANSYS Academic Research license must be placed before ANSYS
CFD license in user preferences. To make this change anslic_admin
utility should be run
`
/ansys_inc/shared_les/licensing/lic_admin/anslic_admin
`
ANSLIC_ADMIN Utility will be run
ANSYS Academic Research license should be moved up to the top of the
list.
