RAOs of UMaine VolturnUS Semi-Sub

Wind & Water
1

Hi all,

I was wondering if anyone has some insight into why the platform pitch (and therefore hub fore-aft) RAOs for the VolturnUS Semi-sub floater exhibit a local maxima in the 0.1-0.125 Hz incoming wave frequency range. Does it have to do with the 1p blade passing frequency which is also in this range? Is there another natural frequency of the system that lies in this range?

all the best, and thank you for any help you’re able to offer!
Jackson

2

Dear @Jackson.Hardin,

Presumably you are referring to Figures 19 and 20 of: https://www.nrel.gov/docs/fy20osti/76773.pdf. These RAOs were generated without aerodynamics and rotor rotation, and so, are not impacted by the blade passing frequency.

I would guess the local maxima is more the result of the geometry of the semisubmersible, the full-system mass distribution. and how the floater is interacting with the wave excitation.

Best regards,

3

Hi Jason,

Yes, thank you for the insight.

best,
Jackson