Dear all,
I am using OpenFAST to simulate the dynamic response of a semi submersible wind turbine under turbulent winds and irregular waves. Here is the pitch time-domain response graph I simulated. The simulation showed a rapid amplitude decay in the first 150 seconds, and after 150 seconds, the pitch amplitude of the wind turbine tended to stabilize. If I want to slow down the transient attenuation of the wind turbine, what parameters should I change or what other methods should I use to slow down the transient attenuation?
Best regards,
Dear @Derrick.Rice,
Did you set the right initial condition for rotor speed ?
In general, one should set the right initial condition of rotor speed according to the mean wind speed.
If you are simulating the 5 MW FOWT, you can find a table containing the mean wind speed versus blade pitch angle in the report “Definition of the 5 MW reference wind turbine”.
Furthermore, i would also suggest to set the platform degrees of freedom to those that correspond to the static equilibrium point.
Best regards,
Riad
Dear @Derrick.Rice,
Adding to @Riad.Elhamoud response, to reduce simulation start-up transients, we generally recommend initializing the rotor speed and blade-pitch angles to their expected (mean) values conditioned on the mean wind speed you are simulating. For floating offshore wind turbines, we additionally recommend initializing the platform surge displacement and platform pitch angle to their expected (mean) values condition on the mean wind speed you are simulating.
Best regards,
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Dear，
Thank you very much for your reply.
After reviewing the information, I have modified the initial simulation conditions you mentioned and successfully reduced the transient response at the beginning of the simulation. Thank you again for your guidance and suggestions.
Best regards.
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Dear @Derrick.Rice
Hope you are doing well.
Just to be precise, the values of the rotor speed as well as the blade pitch angle that correspond to the mean wind speed at hub height could be found in Jason JONKMAN Ph.D. thesis for all mean wind speeds starting from cut-in to cut-out. https://www.nrel.gov/docs/fy08osti/41958.pdf
on the Table 7-1 page 126.
The document i have pointed in my answer https://www.nrel.gov/docs/fy09osti/38060.pdf
contains only the values of the rotor speed as well as the blade pitch angle for the mean wind speed starting from the rated wind speed to the cut-out wind speed.
Best Regards,
Riad