Question on raft_rotor.py, IECKaimal, Rot spectrum

[giannikosk]

I have a question regarding the definition of the rotor averaged wind speed amplitudes U(ω). In the code snippet I am attaching, a Rot variable is defined which does not use any of the spectra in the X, Y, Z directions. It is mentioned that these formulas are derived from the IEC 61400-1-2019 annex C ("Compute turbulence scale parameter Annex C3 of IEC 61400-1-2019") however said anex defines the coherence function and the PSDs in the 3 directions for the Kaimal method. Some complex math is involved in this calculation, and I would like to ask how this equation is defined if there are any sources I can look into to understand the meaning of this derived spectrum. I looked into any publications I could find using Raft, but in most cases this part was not referenced at all.

[dzalkind]

Hi,

It's my understanding that the IEC standards are the wind at a specific point in space. In Rot, we want the spectrum of the rotor averaged wind speed, which we learned from David Schlipf's thesis in Section 5.2.2.

It's probably worth adding this citation somewhere for reference, so let's leave this open until then.

Best, Dan