Analysis Types in openCFS¶
All the files in this tutorial can be downloaded here
.
Several different analysis types are possible in openCFS.
This is illustated in this tutorial by the example of a solid mechanics problem of a cantilever beam.
In a single openCFS input file different analyses can be collected by defining several <sequenceStep index="N">
tags, which will run in sequence.
Typical analyses for the mechanic PDE are:
-
The static analysis computes equilibrium configuration (i.e. the defomation) of the beam for a stationary (static) load.
-
The eigenFrequeny step computes the natural frequencies and corresponding oscillaion modes of the beam.
-
The harmonic analysis computes the steady state response of the structure subject to harmonic loading.
-
The transient step computes the time dependent response of the structure subject to general, time-depedent loading.
Sketch of the domain
CCCCC
CCCC/C
CCCC///C
CCCC/////C
CCC//////C
CCC/////8000000000000000000000000000000000000000000008888 ^ ^
CCC///8 cantilever beam 8 | h /
CCC/800000000000000000000000000000000000000000000008888 v / b
CCC/80000000000000000000000000000000000000000000008888 /
CCC//<----------------------L------------------------> v
CCC//////C
CCC/////C
CCC////C
CCC///C
CCCC
Meshing¶
- Type 'coreform_cubit -batch -nographics -nojournal beam.jou' on the terminal.
- The journal file
beam.jou
from (1.) is used as an input. - Both an ANSYS-cdb mesh file
beam.cdb
and a cubit filebeam.cub5
are created. - Look into the journal file
beam.jou
to see the cubit commands to create the mesh. - These commands could also have been run interactively in Cubit.
- Look through the mesh file to obtain the beam dimensions.
The file beam.cdb
was created this way.
Simulation with CFS¶
The CFS input file is simulation.xml
.
It contains several analysis steps (static, natural frequency, harmonic, transient).
The material file is called mat.xml
using the usual convention.
To run the simulation execute
cfs -p simulation.xml job
which creates text files in history
and the HDF5 output in results_hdf5/job.cfs
.
Both above steps can be done by running the shell scipt run.sh
, i.e. in a terminal change to this directory and run
./run.sh
An an exercise:
- Look into the material file to obtain the material properties
- Study the CFS input and get familiar with each analysis step (step definition, BCs, loads, outputs)
Postprocessing¶
CFS can write output in various formats.
In this example we define text-based history output and field output in the HDF5 format (*.cfs
file).
As an exercise:
- Look at the produced ASCII file in
history
- Load the result in ParaView and try the following things
- Load the correct analysis step (=multi sequence step)
- Display deformed geometry (use the Wrap by Vector filter)
- Switch the Complex Mode for complex valued results
- Animate Harmonic / Modal Results for the corresponding sequence steps
- Animate transient results
Furter Sugesstions¶
- Compare the results with the analytic solution
- Specify a spacially varying load
- Compute the natural frequencies of a free-free beam
- Plot the results in the ASCII file (response of the end-point as a function of time and frequency, respectively)
- What happens if you play with the damping parameter?
- Which effect does the parameter
T
have?