Modal Mass Matrix. Tower

Hi everybody,

After a brief research in the forum and in FAST User’s guide, I have one question.

Is possible to obtain the modal mass and modal stiffness matrices of the tower? I mean, I basically want the mass and stiffness matrices of the tower when the generalized coordinates are the tower modes. Can be obtained from FAST or BNodes?

Thanks in advance.

Dear Aitor,

As discussed in the following forum topic: http://forums.nrel.gov/t/how-to-find-the-paramter-of-the-first-bending-modal-mass-damping-and-stiffnees-coefficients/1594/2, FAST v8 returns the linearized model in first-order form. So, while you can’t get the second-order mass and stiffness matrices (M and K), you can get the same terms normalized by the mass matrix i.e. [ M^-1 ]*[ M ] = I and [ M^-1 ]*K through the FAST v8 linearization analysis. This first-order form should also be amendable for controls design.

That said, a linearization analysis with FAST v7 can be used to obtain the mass and stiffness matrices.

Best regards,

Thank you Jason.

As always you are very helpful.

If is not a problem, another question, where can I find more information about the procedures used by FAST to calculate tower deformations and how merges FAST the multibody model and the tower model?

Thank in advance and best regards,

Aitor

Dear Aitor,

Information on the FAST theory basis is available in the following forum topic: http://forums.nrel.gov/t/coupled-blade-modes-in-fast/314/1.

Best regards,