About the wind turbine loads

Dear Jason,

I have a question about the wind turbine loads. As I know, the 2p loads in the three blade root bending moments will lead to the 3p loads in the tilt and yaw moments.
When I reduce the 2p loads on the blade using individual pitch control, the 3p load in the tilt moment decreases. however, the 3p load in the yaw moment increases, which i cannot interpret.

When I mitigate the 4p components of the blade root bending moments, the similar result can be obtained.

But when I mitigate both 2p and 4p components of the blade root bending moment, both the 3p components of the tilt and yaw moments will decrease.

Is this result right or wrong? Looking forward to your reply. Thanks a lot.

Best regards,
Yunqian Zhang

Dear Yunqian Zhang,

You are correct that 2p-cyclic loads in the rotating frame contribute to 0p and 3p loading in the nonrotating frame for a 3-bladed turbine, which suggests that a reduction in 2p loads in the rotating frame would reduce 3p loading in the nonrotating frame. If your results are not fully consistent with this, have you assessed all six load components in the rotating frame? (The six load components are: in-plane and out-of-blane shear forces, axial forces, in-plane and out-of-plane bending moments, and pitching moment.) For example, the nacelle-yaw moment may not only be influenced by blade-bending, but also by the blade pitching moment; perhaps bending is being reduced but the pitching moment is increased?

Perhaps someone with more experience with the application of linear models and/or multi-blade-coordinate (MBC) transformations can provide further guidance.

Best regards,