Turbsim wind drastic jumps and drops

Wind & Water Computer-Aided Engineering Software Tools
1

Dear Jason,

I am involving in a wind turbine design project. When analyzing FAST loading outputs for DLCs that required atmospheric turbulence, I noticed large jumps or drops in many load sensors (e.g. Fig. 1). These drastic variations leads to complications in designing many subsequent turbine parts.
Because I suspected that it may be my fault in defining many parameters throughout different FAST input files, I went back to CertTest files. Fig. 1 below shows the YawBrMzn load sensor output for Test13 sample model. The model is not modified in any ways and the output is just simply plotted here.
Now the question is that, based on your experience, are these variations realistic? We have problems, for example in selecting yaw drivers for our turbine and the required powers and sizes seem unrealistic. Thanks in advance for helping me.

Regards,
Yahya

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2

Dear Yahya,

I’m not aware of any issues in how FAST calculates the yaw-moments.

Best regards,

3

Dear Jason,

Thank you for your reply. Do you know someone in the FAST development team whom can help me on this issue?

Best Regards,
Yahya

4

Dear Yahya,

I meant to say that the yaw bearing moment you are plotting is what I would expect to see. The turbulent wind creates stochastic loads that cause oscillation in the yaw-bearing moment, with a strong three-per rev (3P) response, which is what I’m seeing in your results.

Best regards,