IEA 15 MW monopile - Displacement SS of tower top with fixed NacYaw

[Fede-274]

I am analyzing the side-to-side oscillations of the IEA 15 MW monopile turbine. Specifically, I am denying the d.o.f. of the nacelle Yaw and imposing a fixed value of the nacelle Yaw (e.g., NacYaw=20°).

I want to evaluate side-to-side oscillations of the tower-top in the direction that already considers NacYaw=20° (i.e., perpendicular to the rotor shaft) and not with respect to the direction with default NacYaw=0°.

I am reading the excel file of possible outputs from ElastoDyn, among the 3 side-to-side displacements highlighted, which one is right for me? or, are there other outputs that I am not considering at the moment?

[jjonkman]

Dear @Fede-274,

The "p" coordinate system mentioned in the convention you state above is a tower-top coordinate system that aligns with the deflection of the tower top, but does not yaw with the nacelle. To convert to the nacelle "n" coordinate system that yaws with the nacelle, you'd have to post-process the outputs in the tower-top coordinate system with a rotation that considers the nacelle-yaw angle (NacYaw). These outputs are not currently available from ElastoDyn, but here are the equations to calculate them:

YawBrTDxn = COS(NacYaw) * YawBrTDxp + SIN(NacYaw) * YawBrTDyp
YawBrTDyn = -SIN(NacYaw) * YawBrTDxp + COS(NacYaw) * YawBrTDyp
YawBrTDzn = YawBrTDzp

I hope that helps.

Best regards,