PAFEC VibroAcoustics

Axisymmetric tweeter model using GiD as the pre-processor



 

A number of pre-processors can be used to create meshes for PAFEC, e.g. FEMAP, GiD, AI Environment, Hypermesh and PIGS. In this example the model has been created using GiD.

Whichever pre-processor is used the overall procedure is similar, e.g:

  • Import geometry, e.g. DXF files
  • Repair geometry
  • Create additional lines and curves
  • Form surfaces
  • Assign mesh densities
  • Mesh surfaces
  • Export data
  • Convert data to PAFEC format
  • Run PAFEC analysis
  • Post-process results

 

Import CAD geometry and repair geometry (if necessary)


 

Note: If care has not been taken in the creation of the CAD information some repair work on the geometry may have to be performed, i.e. if lines do not always meet at co-incident points and lines are not where required for element generation. It is fairly straightforward to delete/create points and lines in the correct place. However, it is best to avoid having to do this repair work by thinking ahead to what the FE model is likely to require when creating the initial CAD data.


 

If quadrilateral elements are required, as in this case for the structural elements representing the former, voice coil, dome and surround, you have to break the area into four sided regions:


 

Former / Dome / Surround detail


 

Create additional lines and form surfaces


 

Assign mesh densities and mesh surfaces


 

For certain catagories of analysis, such as tweeters, the 'Mesh2Paf' wizard converts the geometrical data from GiD into appropriate PAFEC structural and acoustic elements. Additionally creating all other data required for a valid PAFEC data file, such as frequency range and step, microphone positions, etc.


 

Convert to PAFEC data file format


 

The PAFEC analysis is now run and results post-processed

 

Pressure field at 1000 Hz


 

Structural deformation at 1000 Hz


 

Pressure field at 5000 Hz


 

Structural deformation at 5000 Hz


 

Pressure field at 10000 Hz


 

Structural deformation at 10000 Hz


 

SPL (dB) v Frequency (Hz) graph


 

At low frequencies the tweeter radiates omnidirectionally into the half space. At higher frequencies it becomes more directional. Closer inspection of the results shows that the main resonance at 3335Hz is the main axialmode of the structure. The other resonances observed in the frequency range are acoustic cavity mode frequencies.


 

This model is a specially created illustrative example, it is not a commercially available tweeter.

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