Rotor and Nacelle Mass moment of Inertia Tensors

[Ran.Tu]

@Jason.Jonkman

Dear @Xiaogang.Huang,

The 6x6 rigid-body mass matrix generated through the linearization of FAST or OpenFAST should have the following form:

where
m = mass
(x_g,y_g,z_g) = center of mass relative to the platform reference point
(I_11,I_12,…I_33) = inertias relative to the platform reference point.

So, you can calculate the center of mass relative to the platform reference point from the off diagonal entries. Based on knowledge of the center of mass, you can shift the inertias to a different reference point using the parallel axis theorem.

Best regards,

Dear @Jason.Jonkman ,

Thanks you, I have successfully calculated the center of mass (CM) base on lower-left submatix of mass matrix.

Sorry for my limited knowledge about parallel axis theorem, I know how to transfer I11, I22, and I33 from platfrom reference point to CM of RNA. But I don’t know how to transfer I12, I23, and I32 from platfrom reference point to CM of RNA, even I have searched for this theorem.

Could you please type the formula to transfer I12, I23, and I32 from platfrom reference point to CM of RNA?

Regards,
Ran