batch_Fluent_howto.pdf

Batch Execution of FLUENT

Purpose: This document provides a brief description about using FLUENT in batch mode. Starting FLUENT

in the background, monitoring the job and interrupting the solution, if needed, are reviewed. These operations

are demonstrated through examples.

I ntroduction

In addition to using FLUENT interactively through the GUI, it is also possible to run FLUENT in the

background. This type of non-interactive usage is known as batch execution. A typical operational sequence

for a batch run involves setting up the case interactively and creating an inputfile to perform the

computations. As part of the execution, FLUENT will write an outputfile containing the information which

otherwise is displayed in the console window. The inputfile contains a list of text user interface commands

to be executed sequentially.

Batch execution can prove useful in the following situations:

Performing overnight runs with a large number of iterations/ time steps without any intervention

Running a number of jobs in sequential manner

Using common computing resources which require job submission

Reducing the memory usage while handling jobs with very large cell counts

Commands for launching batch jobs on different operating systems are as follows:

Operating System

Startup Command

Details

Unix: C shell

fluent 2d/3d –g < inputfile >

& outputfile &

-g option will launch FLUENT without GUI.

& is a standard Unix feature that indicates

background usage.

Unix: Bourne or

Korn shell

fluent 2d/3d –g < inputfile >

outputfile 2>&1 &

-g option will launch FLUENT without GUI. A

small icon will appear in window taskbar.

Windows

fluent 2d/3d –g/-hidden –i

inputfile

-hidden option will launch FLUENT in

background without any icon.

FLUENT does not write an outputfile on

Windows by default. To enable the transcript feature

in the inputfile , add the following TUI

command:

file/start-transcript outputfile

Batch Options :

FLUENT may need user input while performing some tasks, such as

overwriting files. The inputfile for batch execution needs extra inputs to

handle these situations. File ã Batch Option offers additional control. This

menu includes options to overwrite a file without user confirmation, to

suppress the printing of questions in the outputfile, and to exit in case an error

appears.

Examples of Batch Execution:

1. To run a set of simulations with varying values of pressure at a pressure inlet.

An appropriate inputfile for this situation: boundary.jou

2. To run many jobs in the sequence.

An appropriate inputfile for this situation: sequence.jou

Tips and Troubleshooting

How to stop a batch job?

On a Unix machine, the job owner can create a kill file inside the /tmp directory:

> cd /tmp

> touch exit-fluent

Exits FLUENT after writing case and data files

> touch check-fluent Directs FLUENT to continue iterations after writing case and data files

On a Windows machine, the check point files are to be created at:

c:\temp\exit-fluent

c:\temp\check-fluent

How to monitor a job in batch mode?

FLUENT does not launch a graphic window while running the simulation in batch mode by default. In

order to monitor the job, residual plots can be generated in the form of image file.

On Unix system, the graphics can be redirected to an image file by adding –driver null option in the

startup command.

fluent 2d/3d -gu –driver null < inputfile >& outputfile &

Note that the –g option is changed to –gu

On Windows system, the –hidden option is used to redirect the graphics.

fluent 2d/3d –hidden –i inputfile

A sample inputfile is as follows:

; start iterating

solve/iterate 300

; write image file of residuals

display set-window 0

display hard-copy Residuals_1.jpg

; continue iterating

solve/iterate 500

Product Version: FLUENT 6.2 and onwards

Author: Nilesh Gandhi

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