[SOLVED] Complex output from StessSolve

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RaK
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[SOLVED] Complex output from StessSolve

Post by RaK »

Hi there!

First of all, thanks for this great software, it's serving me well for quite some projects.

Here is my probably stupid question: (How) is it possible to extract the real and imaginary part of displacement within a harmonic analysis of StressSolve simulation?

I have a quite simple resonant test case (tuning-fork like, quarter model, excuse the rough mesh... just a test case), which is driven at the center and the frequency is swept over the resonance via scanning. The "displacement HarmonicMode1" gives nicely the amplitude. In order to access the phase w.r.t. the driving force I'd like to export the complex displacement.
Simply exporting "Displacement Im" yields an empty field.

Thanks in advance for any hints!

Raphael
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ForkDummy.tgz
ElmerGUI project
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Last edited by RaK on 23 Oct 2019, 11:41, edited 1 time in total.
raback
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Re: Complex output from StessSolve

Post by raback »

Hi

Are you sure there should be? The diplacement has a real component unless you have an imaginary source or damping. If the imaginary part is plotted I think it should come out as computed.

-Peter
kevinarden
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Re: Complex output from StessSolve

Post by kevinarden »

From the model manual

Harmonic Analysis Logical
Time-harmonic analysis where the solution becomes complex if damping is defined. The solution algorithm assumes that the diagonal entries in the matrix equation dominates
RaK
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Re: Complex output from StessSolve

Post by RaK »

Hi Peter,

Thanks for the quick response. Sorry, I attached the file w/o damping... With a damping boundary of 1e5 the dip around the resonance in "Displacement HarmonicMode1" as real part is clearly visible. I'm just not sure which variable to export to get to the imaginary part. As mentioned "Displacement Im" does not do the trick

Raphael
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case.sif
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kevinarden
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Re: Complex output from StessSolve

Post by kevinarden »

I would try

Displacement 1 Im
Displacement 2 Im
Displacement 3 Im

for x, y , z respectively
RaK
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Re: Complex output from StessSolve

Post by RaK »

trying...
Components are empty, too.
kevinarden
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Re: Complex output from StessSolve

Post by kevinarden »

Some of the test problems for other solvers are using

Im Displacement 1


do not see a test problem for harmonics in stresssolver
RaK
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Re: Complex output from StessSolve

Post by RaK »

still empty... I think I'll have to dive into the code

Anyway, thanks for your suggestions, thats very much appreciated.
raback
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Re: Complex output from StessSolve

Post by raback »

Hi

When saving VTU output and you don't know what fields you have, don't specify any of them. This will give you all the fields.

You can also test with imaginary force on boundary, Force i Im = Real, i=1,2,3.

-Peter
RaK
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Re: Complex output from StessSolve

Post by RaK »

Hi,

those were actually my first tries. Real and Im force, and all possible combinations of how to put the "Im". When applying an imaginary force without damping, the (real) output is indeed ~0 as the phase really jumps from 0->180deg, but sadly there is no imaginary output.
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