Session: 09-01-07 Wind Energy: Aero-hydrodynamics 7

Paper Number: 136471

136471 - Contribution of Wave Effects to the Horizontal Lf Motions of Floating Offshore Wind Turbines 

Horizontal mean and low frequency motions governed by environmental loads are important for the design of floating wind turbine platforms' mooring system. The related platform slowly varying horizontal offset contributes strongly to both extreme and fatigue mooring line loads. Extreme offset is also a driver for the power cable design. The dynamic responses of INO WINDMOOR floating wind turbine (FWTs) in low frequency surge motion is investigated as a case study. A group of environmental conditions is selected to represent operational conditions with aligned wind and waves.  The relative contributions of wave, as well as of wind, low frequency excitations to the low frequency horizontal motion response of the floating wind turbine are investigated. Simulations were conducted for turbulent wind and irregular waves with an aero-hydro-servo-elastic computational tool with the state-of-the-art force models.

The effect of increasing wind speed in turbine's operational range, in presence of low and moderate sea states, is studied in terms of low frequency motion response of the platform in surge.

A more detailed comparison is presented for a moderate sea-state and rated wind speed, where the effect of waves on slowly varying surge motions is discussed in terms of excitation as well as damping effects, e.g. wave drift damping. The combined wind and wave contributions to the turbine aerodynamic damping is discussed. The additional low frequency surge hydrodynamic damping induced by wave frequency motions imposed on the mooring lines is investigated. It is shown that the aforementioned damping could contribute to reduction of the surge response spectrum in the vicinity of the natural frequency of surge. Further investigations are proposed to form a better understanding of wave and wind relative contributions to slowly varying motions.

Presenting Author: Fatemeh H. Dadmarzi SINTEF Ocean

Presenting Author Biography: I am working in SINTEF Ocean as research scientist since 2021. I got PhD from NTNU-marine hydrodynamics.

Authors:

Fatemeh H. Dadmarzi SINTEF Ocean
Nuno Fonseca SINTEF Ocean
Petter Andreas Berthelsen SINTEF Ocean