Turbine Floater-Tether Coupled Dynamic Analysis Including Second-Order Sum-Frequency Wave Loads for a TLP-Type FOWT (Floating Offshore Wind Turbine)

2013 ◽  
Author(s):  
Y. H. Bae ◽  
M. H. Kim
Keyword(s):  
Dynamic Analysis ◽  
High Frequency ◽  
Second Order ◽  
Offshore Wind Turbine ◽  
Frequency Wave ◽  
Wave Condition ◽  
Sum Frequency ◽  
Coupled Dynamic Analysis ◽  
Resonance Frequencies ◽  
Fully Coupled

In the present study, a numerical simulation tool has been applied for the time-domain turbine-floater-tether fully-coupled dynamic analysis of a FOWT. The fully coupled dynamic analysis includes aero-blade-tower dynamics and control, mooring dynamics, and platform motions. In particular, the effects of second-order sum-frequency wave excitations on the coupled dynamic analysis are investigated. The fully coupled simulations with full blade operation are compared with those with parked condition (without blade rotation). For this purpose, a mono-column TLP with 5MW turbine in 200m water depth is selected as an example. The time histories and spectra of the FOWT motions and accelerations as well as tether top-tensions are presented for the given random collinear wind-wave condition. The shift of original floater natural frequencies due to the inclusion of tower flexural modes is demonstrated. The increase of aero damping in the case of rotating blades is also explained. The second-order sum-frequency wave loading introduces high-frequency excitations near pitch-roll resonance frequencies or lowest tower flexural modes. Its effects are more clearly seen in the blade-parked condition than the blade-fully-operational condition. The increased high-frequency responses may significantly increase tower-top accelerations and accumulated fatigue.

Aero-Elastic-Floater-Mooring Coupled Dynamic Analysis of FOWT (Floating Offshore Wind Turbine) in Maximum Operation and Survival Conditions

2012 ◽  
Author(s):  
Y. H. Bae ◽  
M. H. Kim ◽  
Q. Yu ◽  
J. K. Heo
Keyword(s):  
Dynamic Analysis ◽  
Wind Turbine ◽  
Clean Energy ◽  
Offshore Wind ◽  
Irregular Waves ◽  
Offshore Wind Turbine ◽  
Coupled Dynamic Analysis ◽  
Floating Offshore Wind Turbines ◽  
Mooring Dynamics ◽  
Dynamics And Control

Increasing numbers of FOWTs (floating offshore wind turbines) are planned in the coming years due to their high potential in massive generation of clean energy from ocean-wind. In the present study, a numerical prediction tool has been developed for the fully coupled dynamic analysis of an FOWT system in time domain including aero-loading, blade-rotor dynamics and control, mooring dynamics, and platform motions so that the influence of rotor-control dynamics on the hull-mooring performance and vice versa can be assessed. Hywind spar design with 5MW turbine is selected as an example, and two different environmental conditions, maximum operational and survival conditions, are applied for this study. The maximum operational condition means the maximum environmental condition that wind turbine can work normally, and the survival condition represents the extreme situation without any blade-turbine operation. Through this study, it is seen that the design environments for different structural components of FOWT can be different. The developed technology and numerical tool are readily applicable to the design of any future FOWTs in any combinations of irregular waves, dynamic winds, and steady currents.

Aero-Elastic-Control-Floater-Mooring Coupled Dynamic Analysis of Floating Offshore Wind Turbine in Maximum Operation and Survival Conditions

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Y. H. Bae ◽  
M. H. Kim
Keyword(s):  
Dynamic Analysis ◽  
Clean Energy ◽  
Offshore Wind ◽  
Irregular Waves ◽  
Offshore Wind Turbine ◽  
Coupled Dynamic Analysis ◽  
Floating Offshore Wind Turbines ◽  
Mooring Dynamics ◽  
Dynamics And Control ◽  
The Time Domain

Increasing numbers of floating offshore wind turbines (FOWTs) are planned in the coming years due to their high potential in the massive generation of clean energy from ocean wind. In the present study, a numerical prediction tool has been developed for the fully coupled dynamic analysis of an FOWT system in the time domain including aero-loading, tower/blade elasticity, blade-rotor dynamics and control, mooring dynamics, and platform motions so that the influence of aero-elastic-control dynamics on the hull-mooring performance and vice versa can be assessed. The Hywind spar design with a 5 MW National Renewable Energy Laboratory (NREL) turbine is selected as an example and two different collinear wind-wave-current environmental conditions, maximum operational and survival conditions, are applied for this study. The maximum operational condition means the maximum environmental condition with normal blade-turbine operation and the survival condition represents the extreme situation without any blade-turbine operation. Through this study, it is seen that the ultimate-loading environments for different structural components of the FOWT can be different. The developed technology and numerical tool are readily applicable to the design of any type of future FOWTs in any combinations of irregular waves, dynamic winds, and steady currents.

Coupled Dynamic Analysis of a Tension Leg Platform Floating Offshore Wind Turbine

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Teng Wang ◽  
Hui Jin ◽  
Xiaoni Wu
Keyword(s):  
Dynamic Analysis ◽  
Wind Turbine ◽  
Offshore Wind ◽  
Wind Loads ◽  
Offshore Wind Turbine ◽  
Wave Loads ◽  
Tension Leg Platform ◽  
Floating Offshore Wind Turbine ◽  
Turbulent Wind ◽  
Coupled Dynamic Analysis

The dynamic response of a tension leg platform (TLP) floating offshore wind turbine (FOWT) was analyzed with considering the aero-hydro characteristic of the whole floating wind turbine system including the wind turbine, TLP platform, and tethers. The “aero-hydro” coupled dynamic analysis was conducted in ansys-aqwa with a dynamic link library (DLL) calculating the aerodynamics loading at every steptime based on the blade element momentum theory. Results from the coupled dynamic analysis of TLP FOWT under the condition of turbulent wind and regular wave show that the wind loads influence mainly the low-frequency response of the TLP FOWT. The wind loads have a large impact on the offsets of the TLP away from the initial position while the wave loads influence mainly the fluctuation amplitude of the TLP FOWT. The average TLP pitch response under the wind load is significantly larger due to the large wind-induced heeling moment on the wind turbine. In addition, the tension of tethers at the upwind end is greater than that at the downwind end. The wind loads could reduce effectively the average tension of the tethers, and the tension of tethers is significantly affected by the pitch motion. Results from the coupled dynamic analysis of TLP FOWT under the condition of turbulent wind and irregular wave show that the surge and pitch of TLP result in an obvious increase of thrust of the turbine and the amplitude of torque fluctuation, more attention should be paid to the pitch and surge motion of TLP FOWT.

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