Hi everyone,
I hope you’re doing well.
I’ve used linearization in OpenFAST along with the MBC3 tool to extract the natural frequencies of my system (around 15 modes with different frequencies). Now, my question is:
How can I identify which degree of freedom (DOF) each mode (and its corresponding natural frequency) belongs to?
For example, how can I tell which mode corresponds to fore-aft tower motion, which one is for blade flapwise bending, or platform surge/pitch, etc.?
I have the .lin files, the EigenvectorsForModeShapeVTK.bin file, and also the .mat output from fx_mbc3.
Is there a way to use the eigenvectors or Campbell diagram data to determine the associated DOF for each mode?
Dear @Erfan.Darkhord,
The topic of how to interpret eigenvalues and eigenvectors from MBC3 following OpenFAST linearization has been discussed on several other topics on this forum; I refer you to those.
That said, the recently released Automatic Campbell Diagram Code (ACDC) makes it far easier to interpret OpenFAST eigenanalysis results, including visualization of the mode shapes and automatic plotting of the Campbell diagram. I suggest you use ACDC in place of the old MATLAB MBC3 scripts: GitHub - OpenFAST/acdc: ACDC: Automated Campbell Diagram Code.
Best regards,
Thank you for your response, Mr. Jonkman.
I found the Excel file, but I’m not quite sure how to use it to identify the natural frequency corresponding to each degree of freedom (DOF).
Could you please guide me on how to interpret it?
are these the right file?
Dear @Erfan.Darkhord,
The MBC3 and Campbell Diagram scripts in the MATLAB Toolbox no longer need the old CampbellDiagram.xls spreadsheet, as all of the data needed are generated and handled by the scripts, as documented in the ReadMe here: GitHub - OpenFAST/matlab-toolbox: Collection of Matlab tools developed for use with OpenFAST.
That said, ACDC is what I recommend you use now.
Best regards,
