IEA 15MW VolturnUS-S Mean Platform Pitch

Hi all,

I have a question regarding the IEA 15MW model on the Volturn-US-S Semisub floater.

In my simulations (in QB) I get a mean platform pitch (no wind, no waves) of ~ -1.5°. This is caused by the loaction of the nacelle CM at (-4.72 NacCMxn) and rotor overhang, which offsets the total RNA CM to ~(-7,0,149) and the total floater (RNA+Tower+Floater) CM to (-0.33,0,-1.62). This is turn causes the mean platform pitch of ~ -1.5°.

I have not found any mentioning of this and in the VolturnUS-S report all decay tests oscillate around a mean pitch of zero. A quick test showed that with a positive nacelle CM (+4.72 NacCMxn) the mean pitch is almost zero, but in my mind this doesnt really make sense wrt. the IEA nacelle geometry.

Does anyone have any thought on this or am I maybe overlooking something?

Best regards,


Hi David,

A simulation with the latest VolturnUS semi-sub in still wind and water shows similar results to what you are seeing (below). It’s possible that the report did not include the nacelle CM.

I hope this helps.

Best, Dan

Thanks so much for the clarification Dan!

This is the same behavior that I am seeing based on the input of the OpenFAST model.