Hello everyone!
I am a beginner with OpenFAST. Recently, I encountered some issues while trying to perform a modal analysis on the blades. When using the runCampbell function from the MATLAB toolbox, everything seemed fine, but I noticed that the example was based on OpenFAST 3.0. Therefore, I made some adjustments for the current version (4.1.2) and attempted to use BeamDyn for the calculations. My templateFstFile is 5MW_Land_BD_Linear_Aero.fst, which comes from r-test-main. The program runs without errors, but the final results show many unmapped modes. May I ask what could be the possible reasons for this?
Dear @Xingyu.Liu,
The OpenFAST r-test you are using involves an OpenFAST linearization with dynamic BEM enabled, which means aerodynamic states will be included in the linearized model. These aerodynamic states can influences the stiffness and damping of the physical modes of the structure, but also add modes to the eigensolution that you can ignore in the post-processing of the Campbell diagram. Alternatively, for a similar effect without aerodynamic states, you can enable frozen wake in linearization by changing DBEMT_Mod from 3 to -1.
Moreover, I would generally recommend using the Automated Campbell Diagram Code (ACDC, GitHub - OpenFAST/acdc: ACDC: Automated Campbell Diagram Code) to generate Campbell diagrams from OpenFAST, which replaces the functionality previously supported through the runCampbell.m script and is much easier to use.
Best regards,
Dear @Jason.Jonkman ,
Thank you for your answer, now I understand why those unmapped modes appeared. And also for your kind advice for ACDC.
All best wishes,
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Dear @Jason.Jonkman ,
Thank you again for your recommendation of ACDC. It is more user-friendly.
However, during my use, I noticed that ACDC doesn’t seem to not able to identify modes from CampbellData as identifyModes.m in matlab-toolbox does. Because I am using BeamDyn, I’m not very sure about the physical meaning of each mode calculated. Are there specific settings or alternative approaches that could help address this limitation?
Thanks in advance for your help!
All best wishes,
Dear @Xingyu.Liu,
While ACDC doesn’t identify which mode is which, it does offer a convenient way of visualizing each mode so that you can label it yourself. ACDC also attempts to identify how a given mode changes as a function of wind speed or rotor speed.
If you are having hard time interpreting the visualizations, I would suggest starting simple (with limited degrees of freedom enabled and no aerodynamics), and build up complexity in steps.
Best regards,
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