Diaphram displacement on Helmholtz Resonator

[kevinarden]

The goal was to have the pressure drive the disk, vice the disk drive the pressure. This worked in the plates.sif fille with
Normal Pressure = Equals "Pressure Re"

However in the plates-coupled.sif that change results in no deflection.

[raback]

Hi Kevin,

In the coupled system the equality of pressure is taken care of on the linear system level. If you want a pressure driven system just put some nonzero pressure on the inlet tube (like there was) and remove the constant pressure condition.

The idea of the block matrix approach is to first create the pure Helmholtz and shell problems that form A11 and A22 blocks of a matrix. Then A12 block is added that implements the effect of normal displacement to pressure (normal component of displacement multiplied by i*omega). Likewise, A21 block is added that adds the pressure as a normal force to the shell. This is quite different than the standard weakly coupled way of Elmer. Some problems are rather tricky to solve with such weak methods which is the reason why strong coupling may be used. Particularly near resonance things are difficult with the weak coupling approach.

-Peter

[Gary R]

Well I finally got the coupling problem straightened out and the simulation runs. The only problem left is pulling out the displacement from the linear solver. I fixed the force on the face of the disk and am trying to pull out the disk displacement with the save scalar solver. So far I get the frequency listed in the data.dat file but the displacements are all zero. Attached is the tarball for the whole project and the .sif file being used. If I can get the displacement pull to work, this project will be essentially done. That doesn't say that I won't be fiddling with the design parameters for a while.
As ever, thanks for all of your help.
Gary R

[kevinarden]

I ran it with this test case and it doesn't work either
https://github.com/ElmerCSC/elmerfem/tr ... Structure2

If you look in paraview the output variable is not displacment when using harmonic mode
it is displacement harmonicmode1

May need to use a different variable name, or it is a bug
Work around is that the data can be outputed from paraview