Tetraspar model in OpenFAST

Wind & Water Computer-Aided Engineering Software Tools
1

Dear everyone.

My question is about the OpenFAST simulation of the TetraSpar model (OC6 phase IV).

It includes a triangular keel connected to the main body by 6 keel lines as depicted in image. I was trying to model these elements in MoorDyn, but I cannot figure it out.

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I understand that the keel has to be modelled as a Body, and the keel lines as Lines or Rods. The Body is placed in space with its position and orientation, and the position of its CG is also included. In addition, the keel lines are placed by their starting position in the main body, and end in the keel. In this way, it gives the impression that giving the position and orientation of the keel is redundant.

I wanted to ask if you could include an example of how to include the keel and its lines in MoorDyn.

Thank you very much in advance.
Iñaki

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Dear @Inaki.Zabala,

I’m not fully familiar with the capabilities of MoorDyn, but when NREL has modeled the TetraSpar in OpenFAST, we used MoorDyn for the mooring lines, but did not use MoorDyn for the keel and keel lines. Rather, we modeled the keel and keel lines in SubDyn and HydroDyn. In SubDyn, the keel was modeled as beam elements and the keel lines as pretensioned cable elements.

Best regards,

1 Like
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Hi @Jason.Jonkman

Yes, you are right. Furthermore, you have already indicated in the paper “Modeling the TetraSpar Floating Offshore Wind Turbine Foundation as a Flexible Structure in OrcaFlex and OpenFAST”.

Thank you!

Best regards
Iñaki