Abstract
The local aerodynamic loading on floating offshore wind turbines (FOWTs) is more complex than on bottom-fixed wind turbines due to the platform motions. In particular, the FOWT rotor may start to interact with its own wake and enter a so-called vortex ring state (VRS). However, it is still unclear when, and to what extent, the VRS may happen to floating offshore wind turbines. In this paper, we quantitatively predict the VRS using Wolkovitch’s criterion during the operating conditions of different FOWTs simulated by FAST. The results show that the type of floating foundation has a significant influence on the aerodynamic performance of the rotor. Also, the probability of occurrence of VRS is bigger for the floating platforms that are more sensitive to wave excitations.
Highlights
In order to significantly increase the share of wind energy produced worldwide, wind energy technology is moving from onshore to offshore and from shallow water to deep water
The results show that the type of floating foundation has a significant influence on the aerodynamic performance of the rotor
NREL 5MW turbine mounted on a TLP The vortex ring state (VRS) prediction results of LC1, load case 16 (LC16) and load case 31 (LC31) for the NREL 5MW turbine + MIT/NREL TLP are shown from Figure 3 to Figure 5
Summary
In order to significantly increase the share of wind energy produced worldwide, wind energy technology is moving from onshore to offshore and from shallow water to deep water. Many design challenges need to be solved to make floating offshore wind turbines (FOWTs) economically attractive. One of them concerns the complex aerodynamics of FOWTs. Due to the combined effects of wind and waves, FOWTs often experience large amplitude motions. It is shown that a FOWT can be subjected to four working states [1] when the floating platform undergoes pitching motion: windmill state, turbulence state, vortex ring state, and propeller state. When calculating the aerodynamics of bottom-mounted wind turbines, only the windmill working state and the turbulent working state are considered. The VRS may seriously influence the aerodynamic performance of FOWTs. Leishman [2] reports the effect of the VRS on a helicopter rotor as follows. We can assume that similar negative effects will occur for FOWTs if not controlled appropriately
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
