Free decay test for 15MW RWT UMaineSemi

Wind & Water Computer-Aided Engineering Software Tools
22

Dear Riad,

Please find below the initial conditions for each DoF that were used in the simulation:

INITIAL CONDITIONS

  • OoPDefl: 0 m – Initial out-of-plane blade-tip displacement

  • IPDefl: 0 m – Initial in-plane blade-tip deflection

  • BlPitch(1): 1° – Blade 1 initial pitch

  • BlPitch(2): 1° – Blade 2 initial pitch

  • BlPitch(3): 1° – Blade 3 initial pitch (unused for 2-blade rotors)

  • TeetDefl: 0° – Initial/fixed teeter angle (unused for 3 blades)

  • Azimuth: 0° – Initial azimuth angle for Blade 1

  • RotSpeed: 0 rpm – Initial/fixed rotor speed

  • NacYaw: 0° – Initial/fixed nacelle yaw

  • TTDspFA: 0 m – Initial fore-aft tower-top displacement

  • TTDspSS: 0 m – Initial side-to-side tower-top displacement

  • PtfmSurge: 0 m – Initial/fixed platform surge displacement

  • PtfmSway: 0 m – Initial/fixed platform sway displacement

  • PtfmHeave: 0 m – Initial/fixed platform heave displacement

  • PtfmRoll: 0° – Initial/fixed platform roll angle

  • PtfmPitch: 0° – Initial/fixed platform pitch angle

  • PtfmYaw: 0° – Initial/fixed platform yaw angle

Regarding the updated results:
CompMooring was set to zero on my previous simulation, After enabling CompMooring correctly, I now obtain surge and pitch values that match the journal results closely (Surge ≈ 0.42 m and Pitch ≈ –1.45°).
However, the heave value is still off. I’m getting –0.35 m, whereas the expected value is approximately –0.003 m.

I am attaching the updated graph along with the journal reference values for comparison.

Best regards,
Jittu Vinitha Jose

image
image1089×714 48.8 KB

Table 4 Static offset of IEA 15 MW RWT mounted on Volturn US-S semi-submersible platform in surge, heave and pitch DOFs.

Description Static offset

Surge (m) 0.413

Heave (m) -0.003

Pitch (degree) −1.457
from: Redirecting

23

Dear @Jason.Jonkman @Jisu.Lim
I am running a similar equilibrium test and my heave displacement stabilises around –0.35 m, whereas many reference results show approximately –0.003 m.
Could this discrepancy be related to platform reference definitions, hydrostatics, or mooring configuration?
or is such a difference also something that could be attributed to the characteristics of the IEA 15 MW model?

Any insight into this heave offset difference would be greatly appreciated.

Thank you!

image
image1089×714 48.8 KB

24

I am thinking about the simlation time. Do the athors in the paper use 400 seconds ?