Dear Dr. Jonkman
I conducted a frequency domain analysis on the .out file results of the 15MW wind turbine and found that there were many spectral peaks in the frequency domain. However, I don’t know how to interpret this. I would like to know if the modal characteristics of the blades will be reflected in the acceleration of the tower. Similarly, will the modal characteristics of the tower be reflected in the response of the blades, which means the modal of blade and tower are coupling.
Thank you.
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Dear @KeHao.Qian,
I would expect the tower response to be driven by aerodynamic excitations that are harmonics of the rotational speed (3P, 6P, 9P, etc.). Mean loads (0P), of course, are also important, as well as any imbalances that could result in 1P, 2P, etc. excitation of the tower. Depending on their level of damping, I would also expect the full-system natural frequencies of the structure expressed in a fixed frame of reference (after apply MBC3 to the blade states in a rotating frame of reference)–including tower modes and blade/rotor modes–to show up in the tower response signal.
The blade response is typically expressed in a rotating frame of reference, where I would expect the mean load (0P) plus various harmonics of the rotor speed (1P, 2P, 3P, 4P, etc.) to dominate the response, although you may see some impact of the full-system natural frequencies there as well.
Best regards,