In ANSYS, as in also e.g. COMSOL Multiphysics, you can calculate a far-field acoustic pressure outside the explicit FEM domain. However, whereas in COMSOL Multiphysics you define a certain closed surface on which you calculate the far-field pressure via the Helmholtz-Kirchhoff integral, it is unclear which surface is actually being used in ANSYS (or what is actually being calculated).
René Christensen ,
Far-feild acoustic pressure is measured from the field at a point which is atleast two wavelenghs away from the source.
By subtracting the total pressure from the mean pressure we get the acoustic pressure.
Dinesh Kumar Roshan In this case far-field pressure is really an external pressure calculated outside the domain in a post-processing loop. It is clear how this is done in COMSOL, but I cannot find documentation on how ANSYS does it.
René Christensen
Please share your email address,
I can mail you some documentation.
Looks like you have to define a Far-Field Radiation Surface... which makes sense.
Enquist-Majda, Bayliss-Turkel or PML are different possibilities for radiation boundary conditions.
Nils Wagner Hi Nils. I am not after BCs, but rather how to calculate an external pressure outside of a FEM domain (terminated properly with PMLs or whatever). I think I figured out how it is done, I was just confused as to getting a result even though I don't select a specific surface for the calculation.
Dinesh Kumar Roshan answer is the correct answer.
In ISO 3744, if memory serves me, it translates for practical room size and frequency range into a half hemisphere with a closest distance that is 4x the largest box distance when the radiating object is enclosed in a rectangular box.
/Claes
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