[Roland R]

Hello CFX users,

I would like to calculate a pneumatic silencer which inlcudes an outside plastic housing and a lot of very thin plastic fibers in the housing :

http://www.arcek.com/dosya/urun/ARC-EXP.102379.jpg

It can be calculated with porous domain, I think, but it is important for me to consider the very small pressure fluctuations coming from the pneumatic system. The pressure signal will transform to a spectrum finally. In my opinion, the porous domain is not correct solution because it will damp the small pressure fluctuations significantly which will result incorrect spectrum of course.

Have anybody an idea to solve this problem?

At the moment I think, there is one way to solve the problem exactly: calculate the silencer geometry in 1:1, without simplifications...

Thanks a lot
Roland

[ghorrocks]

I cannot see that link.

You comment is puzzling:

the porous domain is not correct solution because it will damp the small pressure fluctuations significantly which will result incorrect spectrum of cours

Isn't the whole point of a silencer to damp the pressure fluctuations?

Rather than doing this by gut feel, how about you actually work out what is going on. Work out what dissipation acoustic pressure waves will have in the device - this will depend on whether it is a separation or shear based dissipation. Then you should have an idea what pressure loss function is appropriate. Then if the porous model is using that pressure loss function then the porous model is appropriate; if you cannot apply that pressure loss function then the porous approach is inappropriate.