FAST output force decreases when wind speed increases

Wind & Water General
1

Hi
This is my first question, hope it is a meaningful one.

I generate Wind input files using Turbsim, of NTM Wind type , and I only change the ‘URef’ (mean Wind speed at reference height) from 0m/s-25m/s, and then the Wind file are used by FAST.

the figure enclosed is the output of FAST at different Wind speeds .

'for example : 'TwrBsFxt ’ (tower base for-aft shear force)

my question is : why the shear force of Wind speed 20m/s (green line) is smaller than the shear force of Wind speed 15m/s (purple line),

except at the begining of simulation, when the turbine is unstable. the magnitude is proportional to Wind speed.

Regards

Hongbo Zh

0_25trbsFx.jpg
0_25trbsFx.jpg1920×655 83.2 KB

2

Dear Hongbo,

You haven’t described what turbine you are simulating or your simulation settings. However, For a standard variable-speed, pitch-to-feather controlled wind turbine, I would expect the mean thrust load to increase with mean wind speed up to rated wind speed (often between 10-12 m/s, depending on the turbine) and then drop again with increasing wind speed due to the pitch-to-feather operation. Is that what you are seeing?

Best regards,