Dear @Jason.Jonkman ，
I am conducting a simulation test of a semi-submersible wind turbine in simpack. My working condition is set to 12m/s turbulent wind, and JONSWAP spectrum, Hs=6m, Tp=10s, and a time domain simulation of 600s. There seems to be a problem with the pitch angle in my results, there is a large fluctuation between 50s and 250s, as shown in the picture, I performed a similar simulation with Openfast, but there is no such a large fluctuation, I am not too sure I understand what caused it, and would like to ask for your guidance.
Before that, I used simpack and Openfast to carry out the free decay of the pitch angle,and the results showed that it was similar. The pitch frequency of my model was 0.038Hz.
Sincere thanks in advance.
Best regards，
Monge.
Dear @Monge.Low,
In addition to the large oscillation, I’m also surprised that the pitch angle doesn’t have a minimum of 0 deg. But given that you are not using an NREL-developed model, I’m not sure how to help.
Best regards,
Dear @Jason.Jonkman ，
I still haven’t figured out what the problem is, but thank you very much for your reply.
I have another question. I did an FFT analysis of the tower top FA displacements of my semi-submersible model, and I found that the amplitude of the pitch frequency (0.038Hz) is much larger than the tower’s natural frequency (0.335Hz), as the picture shows，is this reasonable? My understanding is that the main cause of tower top displacement is due to platform pitch, is my understanding correct?
Best regards，
Monge.
Dear @Monge.Low,
Certainly the platform-pitch mode can be a large contributor to the tower loading for floating wind turbines atop a semi-submersible.
Best regards,
