[SOLVED] Complex output from StessSolve

General discussion about Elmer
kevinarden
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Re: Complex output from StessSolve

Post by kevinarden »

Apparently it is truly imaginary!
RaK
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Re: Complex output from StessSolve

Post by RaK »

Yea, physics still works :lol: , if only I could see and pass it to another solver :roll:
raback
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Re: Complex output from StessSolve

Post by raback »

Hi

Maybe you could replace "Harmonic Analysis" with "Harmonic Mode" in the sif file. This could help in the postprocessing in this case.


So what is the problem generally: most solvers, also including StressSolver, were initially written as a real valued solvers. Then at a later stage a possibility was added to use the initial matrix equation Mx''+Kx=F also to solve eigenmodes or harmonic solution. In these cases the resulting field is complex so the original matrix equation is made complex on-the-fly. The results for the harmonic case are then copied back to the real valued solution vector, Var % Values. This allows for the visualization of the real part, but not the harmonic part. You still have the full complex solution in Var % EigenVectors, but it is not easily available.

When we were solving some rather cumbersome cases with harmonic FSI coupling it was not enough to do this change to harmonic system on-the-fly since we needed to have full access to the complex displacement field and complex flow field. Hence a new strategy for treating the harmonic case was introduced. There the system is two times bigger and the component 2::2 is associated to "Diplacement Im" and the component 1::2 to "Displacement Im". The changes were quite significant so the old procedure is still maintained as "Harmonic Analysis" and the new one is called with "Harmonic Mode".

For eigenvectors we have similar issue. I guess the primary output method is VTU files. I just added a keyword for ResultOutputSolver that can choose between the type of field the keyword is

Code: Select all

  Eigen Vector Component = String "re" ! or "im" or "abs"

and will commit this after running tests. This is hardly perfect since it will only allow to save either component. One could perhaps have two instances of the solver with different names.

It would be ideal if VTU files would include complex valued datatype. But I guess this is not the case.

-Peter
RaK
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Re: Complex output from StessSolve

Post by RaK »

Hi Peter,

thank you very much for the fast help, "Harmonic Mode" works fine for me.

Cheers
Raphael
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