Analysis Types in openCFS¶
All the files in this tutorial can be
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
- Type 'coreform_cubit -batch -nographics -nojournal beam.jou' on the terminal.
- The journal file
beam.joufrom (1.) is used as an input.
- Both an ANSYS-cdb mesh file
beam.cdband a cubit file
- Look into the journal file
beam.jouto 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.
beam.cdb was created this way.
Simulation with CFS¶
The CFS input file is
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
Both above steps can be done by running the shell scipt
run.sh, i.e. in a terminal change to this directory and run
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)
CFS can write output in various formats.
In this example we define text-based history output and field output in the HDF5 format (
As an exercise:
- Look at the produced ASCII file in
- 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
- 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