Acoustic Wave Propagration of a Cylindrical Wave¶
Problem Definition¶
All the files in this tutorial can be downloaded here
.
This example shows acoustic wave propagation in a transient analysis in 2D. Waves are excited by a sin-burst signal on a circular cylinder. They propagate outwards into a 1/4 domain (2 symmetries have been exploited).
Sketch of the domain
_________________________
|*************************|
|*************************|
|********** air **********|
|*************************|
|*************************|
^ ...***********************|
| .......*******************|
R .........*****************|
| ..........****************|
v ...........***************|
‾‾‾‾‾‾‾‾‾‾‾‾‾‾
<----R--->
Meshing¶
Workflow (see the file run.sh
):
- Mesh the domain, see Cubit file
domain.jou
- The journal file
domain.jou
from (1.) is used as an input. - An ANSYS-cdb mesh file
domain.cdb
is created. - You can also save the created geometry as
domain.cub5
to open it directly on Cubit (optional). - Look into the journal file
domain.jou
to see the Cubit commands to create the mesh. - These commands could also have been run interactively in Cubit.
The file domain.cdb
was created this way.
Simulation with CFS¶
Use an XML-editor (e.g. oXygen or eclipse) to define the simulation input for CFS.
For all the cases, we have the following generic procedure:
The input file (transient.xml
) is the simulation input.
In the file (mat_acou.xml
) the material porperties are defined.
To start the computation run the following command in the terminal
cfs -p transient.xml job
where job
can be any name you choose for the simulation.
CFS will write some output on the terminal, and produce the two files
* job.info.xml
, which contains some details about the run, and
* job.cfs
in the results_hdf5
directory, which you can view with ParaView.
Postprocessing¶
- collect all sensor-array files to one by using
combineSensorArray.py
- look at the field result in ParaView (load pipeline from
post.pvsm
)
Further Suggestions¶
Think about the following questions:
- Time of flight: how much time does the signal take from the excitation to a microphone location in the center of the domain?
- Amplitude decay: A wave with a pressure amplitude of 1 is excited, why is the amplitude in the center of the domain smaller?
- What happens when the wave reaches the boundary of the domain? Apply absorbing boundary conditions (ABC) and compare the results.
- How coarse can the mesh be? How large can the timestep get? Conduct a convergence study ...