the rigid tower (It = diag(Itx, Ity, Itz)) and the rotational inertia of the rotor (Ir = diag(Irx, Iry, Irz)) in the available literature

[cc200528]

Dear community,
I am currently simulating a 5 MW Spar offshore wind turbine. To my understanding, both the tower and blades in OpenFAST are modeled based on their respective elastic properties. However, I would like to treat the blades and tower as rigid bodies, and establish a theoretical model according to the multi-rigid-body model outlined in the attached paper. During the modeling process, I have encountered difficulties in finding the values for the rotational inertia of the rigid tower (It = diag(Itx, Ity, Itz)) and the rotational inertia of the rotor (Ir = diag(Irx, Iry, Irz)) in the available literature. Could you please provide the specific values for the rotational inertia of the tower around its centroid (It) and the rotational inertia of the rotor around its axis (Ir)?Attached is the literature for my reference.
Thank you in advance!
Best regards
Dynamic modeling and simulation of a spar floating.pdf

[jjonkman]

Dear @cc200528,

I don't recall ever calculating the rigid-body inertia matrix separately for the rotor and tower of the NREL 5-MW baseline wind turbine myself. However, you could calculate these using OpenFAST, e.g., following the process discussed in the following topic on our forum: https://forums.nrel.gov/t/rna-inertia-fastv7/2297. To follow this process for the rotor, you'd have to zero-out the mass of the nacelle, tower, and spar. For the tower, you'd have to zero out the mass of the rotor, nacelle, and spar.

FYI: You can always model a floating offshore wind turbine in OpenFAST with rigid tower and blades by disabling their respective degrees of freedom in ElastoDyn (without the need to compute the rigid-body inertia matrix).

Best regards,

[cc200528]

Dear @jjonkman ，

Thank you for your answer.

I have another question. I want to model according to the model in the paper (the paper takes the center of mass of the platform as the coordinate origin, and fast takes the static water surface as the coordinate origin). What parts need to be changed?

Best regards,

[cc200528]

Dear @jjonkman ，

Hope you are doing well. I am a student dedicated to research on the multi-body dynamic response of floating wind turbines. Recently, I have attempted to replicate relevant simulations in Openfast using MATLAB code, particularly for solving the dynamic response of floating wind turbines. In my next step of work, I plan to introduce passive control strategies to explore their potential impact on vibration control of floating wind turbines. This research direction is of great significance to me. Although I have invested considerable effort in coding and optimization, unfortunately, the MATLAB code I developed yields significant discrepancies in the response results of floating wind turbines compared to the official results from Openfast, which has hindered my in-depth understanding and analysis of the research problem to some extent.

Currently, the MATLAB models I have constructed lack sufficient accuracy and functionality to support me in advancing smoothly to this stage of research. Therefore, I sincerely request that you kindly share the MATLAB models for 5MW_OC3_Spar and 5MW_OC4_Semi (if possible) or the modeling about matlab. I believe that these professional and validated models will greatly facilitate my research progress, enabling me to more accurately simulate and analyze the dynamic behavior of floating wind turbines and further explore vibration control strategies on this basis.

I understand that these models may involve a great deal of work and expertise from you or your team. Therefore, I would be deeply honored and incredibly grateful for any help and support you can provide.
I look forward to your reply and sincerely thank you for taking the time to read my request. If you have any further information or discussion needs, please feel free to contact me at any time.

Best regards,

[jjonkman]

Dear @cc200528,

I'm not sure I fully understand your questions.

Regarding a change in reference coordinate system, you can always convert outputs or matrices from one coordinate system to another (such as the full-system COG), e.g., as discussed in the following topic on our forum: https://forums.nrel.gov/t/oc3-hywind-raos/1085.

Regarding MATLAB models, I'm not aware that NREL has developed any MATLAB-based dynamics models of floating offshore wind turbines (FOWT). I would recommend applying OpenFAST for FOWT dynamics.

Best regards,