# Spring controllers in the joint between tower and nacelle

Hello

I have modeled a Floating wind turbine in matlab with multibody dynamics formulas. In the joint where the tower and nacelle are connected to each other I have modeled some control equations with spring-damper in the roll and pitch rotations of nacelle(yaw direction is free and has no control equations). I was wondering if there is any spring-damper in the joint in reality? and if there is, what is the spring and damper coefficient?

Best regards
Vahid Jahangiri

Dear Vahid,

Perhaps I’m not understanding your point, but I’m not aware of any floating wind systems that have a joint located between the tower and nacelle that permits motion in the roll and pitch directions.

Best regards,

Dear Jason

I have uploaded an image that is for Gireesh paper which I have taken from “http://www.iwwwfb.org/Abstracts/iwwwfb26/iwwwfb26_37.pdf” . My model is something like this but not exactly this type. I hope this could help.

Thank you
Vahid Jahangiri

Dear Vahid,

Looking briefly at the paper, it appears that the joint between the tower and nacelle is used to mimic the first-bending mode of the tower. Ideally, you’d choose the spring and damper so that (1) the natural frequency, (2) tower-top deflection for a given thrust, and (3) damping ratio match that of the real system.

Best regards,

Dear Jason

I have searched through various papers to find the natural frequency of Nrel 5 MW nacelle and I couldn’t find it. Do you know what are the frequencies of the nacelle?

Dear Vahid,

It is not the natural frequency of the nacelle you are looking for, but the natural frequency of the tower-bending mode. For floating systems, this tower-bending mode frequency will depend on the mass/stiffness characteristics of the floater and station-keeping system. We have data published for some systems, but I don’t know which system you are modeling (e.g., the MIT/NREL TLP supporting the NREL 5-MW turbine, the UMaine-DeepCwind TLP supporting the NREL 5-MW turbine, or something else?).

Best regards,

Dear Jason
Thanks for your guidance. It is NREL TLP supporting 5MW NREL turbine. The one mentioned in the attached file. but only the properties are the same and my model is a new model with large amplitude motion. I want the natural frequency of the tower-bending mode to validate my work

Dear Vahid,

I’m not sure what you mean when you say, “only the properties are the same and my model is a new model with large amplitude motion,” but the natural frequency of the 1st tower fore-aft bending mode of the MIT/NREL TLP described in Matha’s report is found in Table 6–that is, 0.63 Hz.

Best regards,