Acoustic FE Modelling

[NVHNovice]

Hi all,
I wanted to ask .. how to model an absorbent material in FE? i mean i am trying to build a simple FE model in Matlab and i have a simple cylinder with a force input from a piston at one end and a rigidly backed abosrbent material at the other. the thickness of the absorbent material isnt too small and it has to be modeled as an impedance....
how do i do it?
matlab and acoustics experts pls advice
ashish

 

[ajamnia]

I like to ask your question with another question; what formulation will you be using? Depending on your approach, you may be be able to creat psudo boundary elements which are very long and assume that the field is zero at the boundary.

 

[NVHNovice]

Dear Ajamnia,
Thank you for the help.. i have to do this in two steps.. in one approach i just model it as boundary impedeance and in the second one i have to mesh the absorbant material also.. now i have a rough idea how to do the first step..coz the absorptivity of the material is provided .. but how do i do the modelling of the absorbant material?
pls advice..
i am making the element mass and stiffness matrices on LHS and the load vector on the approach .. where the Galerkins approach is used to get elements of these matrices...
thanks so much ..
pls advice...
thanks again