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Running Ansys Fluent in Batch Mode on a Linux-based Cluster Using LSF Job Schedule

The following are guidelines for running a Fluent 2022 R1 simulation in our CAD Compute Cluster. 

Background

With Ansys, you can read an older project in a newer version of the software, but you cannot view projects created in newer versions from within older releases.

CMC’s Cluster operating system is Linux. It is strongly recommended that you have familiarity with some Linux commands that enable you to move files, check directories, etc. before using our Cluster.

CMC staff implemented a job scheduler from IBM in our Cluster called Load Sharing Facility (LSF). It runs constantly in the background, and LSF accepts simulation requests from all CAD software loaded on the Cluster. CMC provides a list of basic LSF commands for users and a link to the online manual.

Logging into the CAD Compute Cluster

Use an image called CAD Compute Cluster that is launched from the CMC website. See our main Cloud page for details.

https://www.cmc.ca/sn-cmc-cad-compute-cluster-instruction/

https://www.cmc.ca/first-time-initialising-the-cad-compute-cluster/

Preparing your Project on your Workstation

There are several ways to create a Fluent simulation to run in batch mode. This means that a simulation is run without a GUI interface, using a series of instructions entered on a command line.

A user project is created on a local workstation, saved locally in *.cas or other format and uploaded to the CAD Compute Cluster.

In creating a project, you assemble a 2D or 3D model of the system under study, create a mesh over/through the body or bodies of interest, and enter the initial boundary and operating conditions of the simulation.

One common way to run Fluent in batch mode is to prepare a journal file from within Fluent first. A journal file is a series of commands that you send to Fluent, to prepare a project for simulation. A journal file can be recorded from within Fluent.

References for this section:

  • Journal files: Fluent 2022 R1 User’s Guide, Chapter 5
  • Other: Fluent 2022 R1 Tutorials

Writing an LSF Script to Run a Fluent Simulation

An LSF shell script for Fluent is written in a similar fashion to one for other Ansys software. CMC’s Cluster settings restrict all users to a maximum of 32 processors (cores).

Any line starting with # can be read by LSF but not by Ansys. Any line starting with ## is read as a comment by both LSF and Ansys programs.

#/bin/sh

## embedded options to bsub start with #BSUB

## — Name of the job —

#BSUB -J ansys_Fluent_example

## — specify queue from the bqueues list —

#BSUB -q adept

# — specify the number of processors —

#BSUB -n 32

## — Specify the output and error files. %J is the job ID —

## — -o and -e mean append, -oo and-eo mean overwrite —

#BSUB -oo Example_%J.out

#BSUB -eo Example_%J.err

#!/bin/tcsh

fluent 3d -g -t32 -i input_file.jou -scheduler=lsf

Editing Scripts and Extra Disk Space for Larger Simulations

CMC’s Cluster has a built-in Linux editor called VIM that allows you to write scripts in your home directories. Editor VIM is a newer version of the program VI. A list of user commands are available on various websites, including the main Red Hat site:

https://www.redhat.com/sysadmin/vim-commands

Because Fluent creates many temporary files during simulation iterations, users should monitor the number of these files created in their home directories. If disk space becomes limited,  use the /scratch/*user_name* directory disk space provided to you on the Cluster for temporary simulation file storage.

More information about using a /scratch directory is available in the Ansys Fluent manual.

Loading Ansys Fluent in the CAD Compute Cluster

Commands to load Fluent are the same as those for loading Ansys Electronics Desktop (Figure 1).

Figure 1: Loading Fluent Commands

References for this Section:

  • Fluent 2022 R1: Running Fluent Using a Load Manager, Chapter 5

Running a Fluent Simulation using an LSF Job Scheduler

Launch your shell script in the same way as for other Ansys software, using a bsub command in a terminal prompt.

~$ bsub < my_fluent_script.sh

Help for Constructing a Project for Batch Simulations

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