Output variable for Helmholtz Solver

[pilafa]

Hi,

I am using Helmholtz solver for an acoustic problem.

Where could I fine a definition of the postproc values?

I am using VTU format:

Code: Select all

Solver 2 

 Exec interval = Integer 1
 
 Equation = String "ResultOutput"
 Procedure = File "ResultOutputSolve" "ResultOutputSolver"
 !Output File Name = File "IR_test." !or any other output file name of your choice
 Output Format = String "vtu"
 Vtu Format = Logical True
 Binary Output = Logical True
 Exec Solver = String "after timestep"
 Save Geometry Ids = Logical True
 Calculate Loads=True
End 

...and that produces a vector called "pressure wave". What is the meaning of the Magnitude, and the X, Y, Z components? Is it defined somewhere?

Thanks,
PL

[raback]

Hi

The x- and y-components are the Re and Im parts of the pressure.

-Peter

[CrocoDuck]

Hi there! I used the Helmholtz solver a few times and I am slightly confused. In my experience, the results should be pressure wave 1 and pressure wave 2, two scalar fields. Is the pressure wave vector a new feature?

[pilafa]

Thanks for the answer Peter.

Another doubt (more related to physics than Elmer):

If I am concern about the actual pressure "seen" by a submerged solid in a bath of acoustic wave, should I use the x component, or the magnitude of the vector?

Thanks,
Pierre

[mzenker]

Hi,

I would use the magnitude.

HTH,

Matthias

[pilafa]

Hi Matthias,

Ok, thanks.
Then, how do you interpret the imaginary part itself?
Does it has a physical meaning?

Thanks
Pierre

[mzenker]

I don't know right away, sorry.
I have never done acoustics with Elmer, and never used the Helmholtz solver. So I don't know why the pressure has an imaginary part.
All I wanted to say is: AFAIK in general the pressure that whatever fluid exerces on whatever body is a force which always perpendicular to the surface. So if you want to know the pressure and you have calöculated it as a vector, it should be perpendicular to the surface, and its magnitude gives the pressure on that surface.

Matthias