Dear reader,
with the linearization example “5MW_Land_ModeShapes” I could produce very fancy animations with Paraview… - similar to this picture, I followed the instructions mentioned in “vtk-visualization.md”.
However, for the analysis of monopiles the mode shape of the substructure is of major importance since it directly drives the hydrodynamic loading. How is it possible to extract the mode shape for the substructure - similar to this example?
I adapted the matlab script “fx_mbc3”, so that the output is generated in a “mat” format parallel to the default “bin” format. I can now access several data in ocatve - here an example…
Unfortunately, I still don’t know how to get the information to plot the mode shapes…
Can anyone give me a hint please?
BR,
Heike
Dear @Heike.vonWaaden,
The inability to visualize SubDyn members within ParaView through the OpenFAST visualization functionality is a known issue, as documented here: Visualizing Offshore Support Structures · Issue #776 · OpenFAST/openfast · GitHub.
A workaround is to ensure HydroDyn is enabled with Morison elements along the monopile, given that visualization of Morison elements was resolved in the following pull request: Visualization of HydroDyn Morison mesh and MoorDyn lines by andrew-platt · Pull Request #1768 · OpenFAST/openfast · GitHub, which was released in OpenFAST 3.5.1 and newer.
Best regards,
@Jason.Jonkman
Dear Jason,
Thank you very much for your fast answer!
I probably expressed myself in a misleading way… I can visualize offshore support structure after you gave me this hint in my previous question here 
https://forums.nrel.gov/t/create-and-visualize-jacket-structure/6232/2
Now, I just want to plot modes shapes like this:
How can I extract the data for plotting mode shapes using linearization?
BR,
Heike
Dear @Heike.vonWaaden,
Certainly the underlying data needed to plot the modal displacement along the support structure (including tower in ElastoDyn and monopile in SubDyn) is available within the eigensolution, but I’m not aware of a simple way to output in a convenient format for plotting it as you illustrate. I agree that this would be a useful feature to add to OpenFAST.
Regarding the underlying data that is available, the contribution of each degree of freedom (tower bending modes and platform displacement in ElastoDyn, and Craig-Bampton modes in SubDyn) within each eigenmode is expressed in the eigenvector. This data, combined with the tower mode shapes specified in ElastoDyn, and Guyan and Craig-Bampton mode shapes calculated by SubDyn is sufficient to characterize the full mode shapes of the support structure.
Best regards,
@Jason.Jonkman
Dear Jason,
thank you very much for your answer, I appreciate
If I find out how to extract the mode shape data I will post it here 
BR,
Heike
Dear Heike,
I’ve got the same question as you, I’ve tried to extract the mode shape data and plot it with Paraview but the only available fields are velocities and accelerations, not displacements to give plots like the ones you posted. Did you find a solution?
Best wishes,
Abdirahman
Dear @Abdi.SheikHassan,
The deflections / displacements are directly visualized through Paraview given that the geometry is shown in the deflected state. I suppose what you want is the displacement perturbation from the undeflected state. The undeflected state can also be visualized. I guess what is missing is a convenient way to export the differences between the deflected and undeflected state.
FYI: The new Automatic Campbell Diagram generation Code (ACDC) tool now provides a quite convenient way of automating the generation of Campbell diagrams and visualizing mode shapesf using OpenFAST: GitHub - OpenFAST/acdc: ACDC: Automated Campbell Diagram Code. I would suggest using that over the old MBC3 + Eigenanalysis + ParaView approach.
Best regards,
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Dear @Jason.Jonkman,
Thanks for the pointer. I’m trying to compare the results of modal analysis from openFAST against another program I’m using, and it would be helpful to try and extract a plot similar to the one from my other program, which is simply plotting the eigenvectors:
Is that something that can be extracted from openfast?
Best wishes,
Abdirahman
Dear @Abdi.SheikHassan,
Indeed, it looks like you want a convenient way of exporting the mode shape deflection relative to the undeflected state. This information is certainly available in the eigensolution, but is not so convenient to export it from OpenFAST currently.
I’ve now added this as a feature request for ACDC: Feature Request -- Add a Convenient Way to Export the Mode Shapes · Issue #6 · OpenFAST/acdc · GitHub.
Best regards,
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