HowTo:ansys

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ANSYS Mechanical

Important Note: This software is provided on the basis of a "hosting" model. This means that users who want to run this software on our cluster will have to supply a license that supports the run.

This is a help file on using the Mechanical Engineering structural code "ANSYS Mechanical" on our systems. This software requires a user-supplied license. The software is only made available to persons who belong to a specific Unix group. See details below.

What is ANSYS Mechanical ?

ANSYS Mechanical is a Mechanical Engineering software that uses finite element analysis (FEA) for structural analysis. It covers a large range of applications ranging from geometry preparation to optimization. You can model advanced materials, complex environmental loadings and industry-specific requirements in areas such as offshore hydrodynamics and layered composite materials.

It can be used interactively and supplies a graphical user interface. It can also run in batch mode, if the required time for solving a problem is too long for interactive use. The latter situation is the standard if you are using it on CAC machines.

Version

The most current version on our systems is Ansys-18.

Location and Access

ANSYS Mechanical runs under the Linux operating system.

The program is located in /global/software/ansys.

To use it, you have to be covered by a user-supplied license. It is furthermore required that you sign a statement. We will confirm the statement, and you will then be made a member of a Unix group fluent (so called for "historical" reasons), which enables you to run the software. Contact us if you are in doubt of whether you qualify to run ANSYS on our system or if you are looking for options for access to a license.

Licensing

To use ANSYS, you have to provide us with a license. The software is only accessible to users who are covered by such a license and are members of the "fluent" Posix group (so called for historical reasons). To be included in that group you need to complete a statement that you can download here. Note that prior inclusion in the fluent group is now void as the licensing terms for the software have changed. If you are in doubt, please contact us at [mailto:"cac.help@queensu.ca" cac.help@queensu.ca].

The license is "seat limited" and "process limited".

The number of seats and process available to you depends on the license under which you are covered

Running ANSYS

Setup

The setup for ANSYS on Frontenac is done via module. Type:

module purge --force
module load ansys/ext181
export ANSYSLMD_LICENSE_FILE={port}@{license server address}

on the workup node or include these commands in your setup (.bash_profile) file. Note that this is "purging" the present setup which may make the shell in which this done unusable for running other software. The setting of the environment variable ANSYSLMD_LICENSE_FILE points the system to the correct license server and port. This information is dependent on the user (substitute the information in the curly brackets).

Note

You have to be in the fluent Unix group for this to work on either system, as access permissions prevent general users from accessing ANSYS software.

Batch runs

ANSYS can (and usually must) be run in batch mode. Since you likely have access to ANSYS on your local machines, most interactive work should be done there, whereas the computationally intensive runs can be executed on a parallel system such as ours. For this, data and commands are written into a text file written in ANSYS Parametric Design Language (APDL) which is used to specify the system and describe the Analysis to be performed. Here is the top of an input file (the full file is too long to be displayed here):

/prep7
ET,1,SOLID185, ,2
MP,EX,1,70e09
MP,EY,1,70e09
MP,EZ,1,60e09
MP,NUXY,1,0.33
MP,NUYZ,1,0.30
MP,NUXZ,1,0.30
MP,GXY,1,26.5e09
MP,GYZ,1,22e09
MP,GXZ,1,22e09
*AFUN,DEG
thetax=0.000000
thetay=0.000000
fx= 0
fy= -1000
fz= 0
fxp= fx
fyp= fy*(cos(thetax)) - fz*(sin(thetax))
fzp= fy*(sin(thetax)) + fz*(cos(thetax))

[...]

Let's call this file "testsys.txt". The analysis can now be performed by calling ANSYS directly from the command line

ansys181 -b -i testsys.txt

In this case, output is sent to the screen, and output files are given the default name "file.*". No further input from the user is required. Once everything works you could submit this job into the background (using bash) by typing

ansys181 -b -i testsys.txt > test.out 2>&1 & 

This would redirect standard output and standard error to test.out. The point is that ANSYS is run non-interactively this way, i.e. we can use the same technique to submit a production job to the scheduler, as shown in the next section.

Production runs

To submit a production job on our clusters, you must use the scheduler. To obtain details, read through Sun Grid Engine (SW cluster) or SLURM (Frontenac). Production jobs that are run without scheduler will be terminated by the system administrator.

On Frontenac, the scheduler in use is SLURM. Here is a SLURM example script of an ANSYS production job:

#!/bin/bash
#SBATCH --job-name=ansys-test
#SBATCH --mail-type=ALL
#SBATCH --mail-user={email address}
#SBATCH --output=STD.out
#SBATCH --error=STD.err
#SBATCH --nodes=1
#SBATCH --ntasks=1
#SBATCH --cpus-per-task=8
#SBATCH --time=00:30
#SBATCH --mem=1G
module purge --force
module load ansys/ext181
export ANSYSLMD_LICENSE_FILE={port}@{license server address}
ansys181 -np $SLURM_CPUS_PER_TASK -b -i testsys.txt -o test.out -j test

Here we are running the file "testsys.txt" using 8 processors on a parallel machine. The output and any error messages from the system are re-directed to a file called "slurm-XXXXX.out" (where XXXXX is the job number).

The --time option is used to specify a time limit. If it is omitted you are assigned a default limit. It is best to specify this limit, and choose it to be slightly longer than the largest expected execution time. This will make the job harder to schedule, but it will ensure that the job is not terminated before it finishes. Note that time limits are "hard", i.e. the job will be stopped when it exceeds its limit. This is necessary to make efficient scheduling possible.

The --mem option is used to specify a memory limit. If it is omitted you are assigned a default limit. It is best to specify this limit, and choose it to be slightly larger than the largest expected memory usage. This will make the job harder to schedule, but it will ensure that the job is not for exceeding its memory allocation. Note that memory limits are "hard", i.e. the job will be stopped if it exceeds its allocated memory. This enable efficient memory allocation.

Parallel jobs of longer runtime should only be run in batch using SLURM. The number of processors "8" specified in our example script appears only once, in

#SBATCH --cpus-per-task=8

which is where you let SLURM know how many processors to allocate to run the program. The internal environment variable SLURM_CPUS_PER_TASK will automatically be set to this value and can then be used in the ansys command line.

All processes are allocated within a single node. This means that the size of the job is restricted by the number of cores on a node. Once the script has been adapted (let's call it "ansys.sh"), it can be submitted to SLURM by

sbatch ansys.sh

from the login node. Note that the job will appear as a parallel job on the "squeue" command.

Further Help

ANSYS Mechanical is a complex software, and requires some practice to be used efficiently. We can not explain it use in any detail here.

The documentation for ANSYS can be access from inside the program GUI (WorkBench).

The documentation is subject to the same license terms as the software itself, i.e. you have to be signed up as a user in order to access it.

If you are experiencing trouble running a batch command script, check carefully if the sequence of commands is exactly in sync with the program. This might mean typing them in interactively as a test. If you have problems that you cannot resolve through the documentation, contact user support by sending email to cac.help@queensu.ca.