disk: F = 0.5ρACdV2, where F is the thrust force on the disk; A is the
disk area; Cd is the drag coefficient,which is assumed to be 1.9 according
to the DNV rule (DNV, 2010); ρ is the density of the air; and V is the relative
wind velocity. In the test, the wind velocity and wind thrust were
both downscaled by Froude scaling. The diameter of the disk is then determined
based on the prototype thrust curve and the designed wind
velocity. The diameter of the large disk is 185 cm, and the diameter of
the small disk is 15 cm. The small disk is used to model the thrust
force under extreme wind conditions, and the large disk is used to
model the thrust force under operational conditions. The centrifugal
forces, gyromoment and aerodynamic dampingwere not taken into account.
It should be noted that, in the operational sea states tested, the
STC was still in the survival conditions, i.e. with the MWL and SUB
modes. The wind sensor was installed between the fans and the
model at a height of approximately 1.5 m above the SWL.