Applicability of the document

[yinghanguan]

I am looking at the document FASTLoads.doc of the ElastoDyn module in openfast. The meaning of the symbols and the standard of the coordinate system are unclear, so I cannot understand the derivation of the formula. Can you provide some information to help me understand it?

[jjonkman]

Dear @yinghanguan,

If you haven't already, I would suggest studying the Unofficial ElastoDyn Theory Manual documents in the order listed here: https://openfast.readthedocs.io/en/main/source/user/elastodyn/index.html. For example, the coordinate systems are explained in document # 2. FASTLoads.doc is document # 5, which can't really be understand without first understanding documents # 1-4. Unfortunately, we have not yet been budgeted to formalize these documents into an official ElastoDyn Theory Manual.

If you have a specific question, please ask, but we can't describe all variables without a budget to formalize the official ElastoDyn Theory Manual.

Best regards,

[JalalHeidari]

Dear @jjonkman,

Considering these DOF in Elastodyn:

True TwFADOF1 - First fore-aft tower bending-mode DOF (flag)
True TwFADOF2 - Second fore-aft tower bending-mode DOF (flag)
True TwSSDOF1 - First side-to-side tower bending-mode DOF (flag)
True TwSSDOF2 - Second side-to-side tower bending-mode DOF (flag)

I wanted to know whether these equations in FastLoads.doc are the related equations:

I cannot understand the variables. Can you please clarify them in terms of OpenFast inputs and outputs? Any of these variables come from AeroDyn?

[jjonkman]

Dear @JalalHeidari,

The equations you are referring to from the ElastoDyn Theory Manual explain how the tower-base loads are calculated via the load summation method, including contributions from the rotor-nacelle assembly, yaw bearing weight/inertia, tower weight/inertia, and tower aerodynamic loads. The later are calculated and output from AeroDyn, which is passed as input to ElastoDyn.

The variables used in these equations are described earlier in the ElastoDyn Theory Manual.

Best regards,