FLUENT

To load the default version of FLUENT module, use  module load ansys. To select a particular software version, use module load ansys/version. For example, use  module load ansys/17.2  to load FLUENT version 17.2 on Cardinal. 

When you log into cardinal.osc.edu you are actually logged into a Linux box referred to as the login node. To gain access to the multiple processors in the computing environment, you must submit your FLUENT analysis to the batch system for execution. Batch jobs can request multiple nodes/cores and compute time up to the limits of the OSC systems. Refer to Batch Limit Rules for more info.  Batch jobs run on the compute nodes of the system and not on the login node. It is desirable for big problems since more resources can be used.

Interactive Batch Session

Interactive mode is similar to running FLUENT on a desktop machine in that the graphical user interface will be sent from OSC and displayed on the local machine. Interactive jobs are run on compute nodes of the cluster, by turning on X11 forwarding. The intention is that users can run FLUENT interactively for the purpose of building their model and preparing their input file. Once developed this input file can then be run in non-interactive batch mode.

To run interactive FLUENT GUI, a batch job need to be submitted from the login node, to request necessary compute resources, with X11 forwarding. Please following the steps below to use FLUENT GUI interactively:

1. Ensure that your SSH client software has X11 forwarding enabled
2. Connect to Cardinal system
3. Request an interactive job. The command below will request one whole node with 28 cores ( -N 1 -n 28), for a walltime of one hour (-t 1:00:00), with one FLUENT license (modify as per your own needs):

   sinteractive -N 1 -n 28 -t 1:00:00 -L ansys@osc:1,ansyspar@osc:24

4. Once the interactive job has started, run the following commands to setup and start the FLUENT GUI:

   module load ansys
   fluent 
   

Non-interactive Batch Job (Serial Run Using 1 Base Token)

A batch script can be created and submitted for a serial or parallel run. You can create the batch script using any text editor you like in a working directory on the system of your choice.

Below is the example batch script ( job.txt) for a serial run with an input file (run.input) on Cardinal:

#!/bin/bash
#SBATCH --job-name=serial_fluent
#SBATCH --time=1:00:00
#SBATCH --nodes=1 --ntasks-per-node=1
#SBATCH -L ansys@osc:1
#
# The following lines set up the FLUENT environment
#
module load ansys
#
# Copy files to $TMPDIR and move there to execute the program
#
cp test_input_file.cas test_input_file.dat run.input $TMPDIR
cd $TMPDIR
#
# Run fluent
fluent 3d -g < run.input  
#
# Where the file 'run.input' contains the commands you would normally
# type in at the Fluent command prompt.
# Finally, copy files back to your home directory
cp *   $SLURM_SUBMIT_DIR 

As an example, your run.input file might contain:

file/read-case-data test_input_file.cas 
solve/iterate 100
file/write-case-data test_result.cas
file/confirm-overwrite yes    
exit  
yes  

In order to run it via the batch system, submit the job.txt file with the command: sbatch job.txt 

Non-interactive Batch Job (Parallel Execution using HPC token)

FLUENT can be run in parallel, but it is very important that you read the documentation in the FLUENT Manual on the details of how this works.

In addition to requesting the FLUENT base license token (-L ansys@osc:1), you need to request copies of the ansyspar license, i.e., HPC tokens (-L ansys@osc:1,ansyspar@osc:[n]), where [n] is equal to the number of cores you requested minus 4.

Parallel jobs have to be submitted to Cardinal via the batch system. An example of the batch script follows:

#!/bin/bash
#SBATCH --job-name=parallel_fluent
#SBATCH --time=3:00:00
#SBATCH --nodes=2 --ntasks-per-node=28
#SBATCH -L ansys@osc:1,ansyspar@osc:52
set echo on   
hostname   
#   
# The following lines set up the FLUENT environment   
#   
module load ansys
#      
# Create the config file for socket communication library   
#   
# Create list of nodes to launch job on   
rm -f pnodes   
cat  $PBS_NODEFILE | sort > pnodes   
export ncpus=`cat pnodes | wc -l`   
#   
#   Run fluent   
fluent 3d -t$ncpus -pinfiniband.ofed -cnf=pnodes -g < run.input