Overhang moment and mooring pretension

Wind & Water Computer-Aided Engineering Software Tools
1

Dear @Jason.Jonkman

  • I was running static equilibrium simulation (no wind, no wave) for OC3 Hywind and i obtained that the static equilibrium position is zero valued 6D vector. I was also thinking about how the structure will remain in equilibrium and there is an overhang due the RNA. For me, there is some applied moment to counteract the overhang moment. right ? This " restoring moment "is calculated automatically by MoorDyn or its added in order to force the structure to be in equilibrium at zero?

  • The pretension used in OC3 Hywind exists when using MoorDyn or just used when using the linearized mooring line stiffness model ?

Best Regards,

Riad

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Dear @Riad.Elhamoud,

Iā€™m not sure I fully understand your questions.

I would expect the NREL 5-MW baseline turbine atop the OC3-Hywind spar to have a nonzero mean surge and pitch in the absence of wind and wave excitation due to the overhanging weight of the rotor-nacelle assembly. The hydrostatic and mooring restoring will limit the amount of tilt arising from the overhanging weight, but the tilt will not be zero.

If you have MoorDyn or another mooring module enabled, the pretension will be accounted for by the mooring module

Best regards,

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