Learning Forum

[CAP_NJ]

Dear all,

I am struggeling with the acoustic pressure fluctuation extracted by the FWH acoustic model (Gutin as well as classic FWH). After reaching a statistically steady solution I try to extract the acoustic pressure fluctuation and ahould get a fluctuation around ZERO. This is not the case for my simualtion. What is the problem there? Any ideas? I guess it has something to do with the atmospheric pressure the fwh model uses tio extract the acoustic pressure fluctuation. Is the fwh model uses kind of a averaged pressure of the domain or the reference pressure of the reference values dialog box? Any help is welcome! Thanks in advance!

[Federico]

Hello, 

what are you using as the Reference Acoustic Pressure when setting up FW-H?

[CAP_NJ]

Sorry to bother you again but I was wondering weather you have any further ideas? Thanks and best regards!

[CAP_NJ]

Hi Frederico,

thanks for your answer!!! I am using the default 2e-5 Pa (which I gues has something to do with the human hearing limits) reference pressure.

[CAP_NJ]

In the theory guide is the general following definition:

And then after the derivation and some assumptions from the stokes FWH formulation it gives the following relations for the pressure fluctuation p' (T thickness and L loading term):

I dont get where it calculates the average pressure (like in the first relation p_0), which must be subtracted to get a fluctuation around zero???

There was a similiar post, but no answer yet.

https://innovationspace.ansys.com/forum/forums/topic/acoustic-pressure-calculation-les-fh-w/