Dear all,
I would like to consult some questions about the derived principle of TMD.I learned from the OpenFAST guidebook that the motion equation of the FOWT system is derived from the KANE equation. After adding TMD to FOWT, should the force exerted by TMD on the FOWT system be attributed to generalized inertial force or generalized active force? In my understanding, as an additional degree of freedom for FOWT, the inertia force of TMD should be attributed to the generalized inertia force, and the elastic and damping forces of TMD should be attributed to the generalized active force? Is this understanding correct?
Best regards.
Dear @Derrick.Rice,
The ElastoDyn module of OpenFAST uses equations of motion derived through Kane’s method. However, TMDs in OpenFAST are modeled via the structural control (StC) submodel of ServoDyn and the equations of motion solved by StC are not derived through Kane’s method; the theory basis of StC is documented here: 4.2.12. Structural Control (SrvD) — OpenFAST v3.5.4 documentation. The impact of the TMD on the ElastoDyn system of equation are treated as external applied loads (that end up as generalized active forces in ElastoDyn). The OpenFAST glue code handles the input-output coupling between ElastoDyn and ServoDyn/StC.
Best regards,
Thank you very much for your reply
The glue code you mentioned is used to couple the input or output between ElastoDyn and ServoDyn/StC modules. I would like to ask what kind of glue code is, how to couple it together, or is there any document that provides a detailed introduction to glue code in OpenFAST? Could you give a brief introduction?
Best regards.
Dear @Derrick.Rice,
The existing glue code that involves an implicit loose coupling scheme has been discussed in other topics, e.g., Integrating HydroDyn with Multibody Dynamics Model in Simulink for Two-Way Data Interchang and Loads and response transferring in OpenFAST · Issue #282 · OpenFAST/openfast · GitHub.
We are currently working on a paper to be submitted to the Wind Energy Science journal that explains the existing implicit loose coupling approach we’ve implemented within OpenFAST, as well as the new tight coupling approach we are finalizing now. We anticipate submitting this paper to WES soon.
Best regards,