scholarly journals Influence of an Integral Heave Plate on the Dynamic Response of Floating Offshore Wind Turbine Under Operational and Storm Conditions

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 6122
Author(s):  
Yichen Jiang ◽  
Guanqing Hu ◽  
Zhi Zong ◽  
Li Zou ◽  
Guoqing Jin
Keyword(s):  
Vertical Motion ◽  
Offshore Wind ◽  
Hydrodynamic Performance ◽  
Offshore Wind Turbine ◽  
Fluid Viscosity ◽  
Operational Conditions ◽  
Hydrodynamic Damping ◽  
Motion Responses ◽  
Heave Plate ◽  
Storm Condition

The hydrodynamic performance of the floating foundation for offshore wind turbines is essential to its stability and energy harvesting. A semi-submersible platform with an integral heave plate is proposed in order to reduce the vertical motion responses. In this study, we compare the heave, pitch, and roll free decay motions of the new platform with a WindFloat-type platform based on Reynolds-Averaged Navier-Stokes simulations. The differences of the linear and quadratic damping properties between these platforms are revealed. Then, a FAST (Fatigue, Aerodynamics, Structures, and Turbulence) model with the consideration of fluid viscosity effects is set up to investigate the performance of the new platform under storm and operational conditions. The time-domain responses, motion spectra, and the mooring-tension statistics of these two platforms are evaluated. It is found that the integral heave plate can increase the viscous hydrodynamic damping, significantly decrease the heave and pitch motion responses, and increase the safety of the mooring cables, especially for the storm condition.

Offshore Wind Turbine Coupled Motion in Regular Waves

2020 ◽  
Vol 54 (2) ◽  
pp. 5-16
Author(s):  
Bao-Ji Zhang ◽  
Gao Yu ◽  
Wen-Xuan She
Keyword(s):  
Wind Turbines ◽  
Wave Force ◽  
Offshore Wind ◽  
Hydrodynamic Performance ◽  
Offshore Wind Turbine ◽  
Theoretical Principle ◽  
Regular Waves ◽  
Offshore Wind Turbines ◽  
Floating Foundation ◽  
Motion Responses

AbstractThis study aims to accurately predict the hydrodynamic performance and motion responses of offshore wind turbines on the basis of computational fluid dynamics (CFD) theory. Continuous and Navier-Stokes (N-S) equations are employed as control equations, and the k-ε model is used as a turbulence model. The finite difference method is utilized to discretize the equation. The Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) algorithm is applied to solve the control equation, and the volume-of-fluid (VOF) method is used to capture the free surface. The numerical wave tank of irregular wave is also established. The hydrodynamic performances and motion responses of the offshore wind turbines under regular waves are studied. First, we assume a floating foundation without the influence of a rotational fan and examine its motion responses and wave force in three typical sea conditions, namely, Levels 5, 6, and 7. Thereafter, we use a series of force and torque acting on the rotating center of the offshore to substitute for the influence of the rotational fan on the floating foundation. Then, we study the hydrodynamic performance influenced by blade rotation of the floating foundation in various sea conditions and three wind speeds, namely, 5, 8, and 11 m/s. Research results can provide usable theoretical principle and technical support for the investigation of the hydrodynamic performance and motion responses of similar offshore wind turbines.

Dynamic Response of a Semi-Submersible Floating Offshore Wind Turbine in Storm Condition

2012 ◽  
Vol 260-261 ◽  
pp. 273-278 ◽  
Author(s):  
Hai Tao Wu ◽  
Jin Jiang ◽  
Jing Zhao ◽  
Xiao Rong Ye
Keyword(s):  
Dynamic Response ◽  
Wind Turbine ◽  
Time History ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Offshore Platforms ◽  
Hydrodynamic Load ◽  
Floating Offshore Wind Turbine ◽  
The Time Domain ◽  
Storm Condition

The paper focuses on a semi-submersible floating offshore wind turbine (FOWT) and analyses its dynamic response in storm condition. The wind load is calculated based on wind block model; the hydrodynamic load is modeled using Potential Theory and Morison Equation. The time-domain dynamic response of the FOWT is simulated by SESAM software with duration of 3 hours. The performance of the FOWT is analyzed based on time history responses and response spectrums. The results show some unique characteristics that differ from offshore platforms and the analysis proofs that the performance is acceptable and the design is reliable.

CFD Simulation of Semi-Submersible Floating Offshore Wind Turbine Under Pitch Decay Motion

2019 ◽  
Author(s):  
Yu Wang ◽  
Hamn-Ching Chen ◽  
Guilherme Vaz ◽  
Simon Burmester
Keyword(s):  
Wind Turbine ◽  
Cfd Simulation ◽  
Flow Characteristics ◽  
Hydrodynamic Pressure ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Natural Period ◽  
Hydrodynamic Damping ◽  
Computational Data ◽  
Computational Fluid Dynamics Cfd

Abstract The application of a computational fluid dynamics (CFD) code to simulate the response of a semi-submersible floating wind turbine under pitch decay motion was investigated in this study. Estimation of the natural period, the hydrodynamic damping and the flow characteristics were the main focus of this study. An extensive verification study of the simulation results was conducted to improve the confidence and reliability of the numerical simulation by the estimation of the numerical errors and uncertainties. The time series of pitch motion was plotted against model test data. In addition, the pitch period and hydrodynamic damping were calculated and compared to experimental data. Detailed flow characteristics as vorticity field and hydrodynamic pressure field on the floater surface were illustrated after post processing of the computational data. The results of the flow characteristics suggest that the heave damping plates were a major contributor to the hydrodynamic damping of this floater in pitch decay.

Prediction of Short-Term Extreme Response of Floating Offshore Wind Turbine Under Storm Condition

2020 ◽  
Author(s):  
Zhi Zong ◽  
Guanqing Hu ◽  
Yichen Jiang ◽  
Li Zou
Keyword(s):  
Wind Turbine ◽  
Offshore Wind ◽  
Irregular Waves ◽  
Offshore Wind Turbine ◽  
Frequency Interval ◽  
Short Term ◽  
Two Phase ◽  
Floating Offshore Wind Turbine ◽  
Motion Responses ◽  
Extreme Response

Abstract To predict the short-term motion responses of floating offshore wind turbine under extreme wind-wave excitation, a numerical model based on the two-phase flow finite volume method was developed. In this paper, uni-directional irregular waves composed of 100 cosine waves with equal frequency interval were simulated by the wave forcing technique, resulting in the measured spectrum in accordance with the target spectrum. Then, a 100-seconds wave segment containing the maximum wave height was selected for fully coupled dynamic analysis of the OC4-DeepCwind system in CFD, and the results were compared with those of FAST under the same wind and wave sea state. It was found that the motion responses of heave and pitch motion responses predicted by two methods agree well. The second-order slow drift force generated in CFD led to the difference in surge motion. The predicted sway, roll, and yaw motions by these two methods were also compared. In addition, significant differences between two methods’ predictions on mooring tension were found.

scholarly journals A New Conceptual Design and Dynamic Analysis of a Spar-Type Offshore Wind Turbine Combined with a Moonpool

Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3737 ◽  
Author(s):  
Thanh Dam Pham ◽  
Hyunkyoung Shin
Keyword(s):  
Wind Turbine ◽  
Bending Moment ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Operational Conditions ◽  
Floating Offshore Wind Turbines

Floating offshore wind turbines promise to provide an abundant source of energy. Currently, much attention is being paid to the efficient performance and the economics of floating wind systems. This paper aims to develop a spar-type platform to support a 5-MW reference wind turbine at a water depth of 150 m. The spar-type platform includes a moonpool at the center. The design optimization process is composed of three steps; the first step uses a spreadsheet to calculate the platform dimensions; the second step is a frequency domain analysis of the responses in wave conditions; and the final step is a fully coupled simulation time domain analysis to obtain the dynamic responses in combined wind, wave, and current conditions. By having a water column inside the open moonpool, the system’s dynamic responses to horizontal and rotating motions are significantly reduced. Reduction of these motions leads to a reduction in the nacelle acceleration and tower base bending moment. On the basic of optimization processes, a spar-type platform combined with a moonpool is suggested, which has good performance in both operational conditions and extreme conditions.

scholarly journals Numerical Simulations for Installation of Offshore Wind Turbine Monopiles Using Floating Vessels

2013 ◽  
Author(s):  
Lin Li ◽  
Zhen Gao ◽  
Torgeir Moan
Keyword(s):  
Time Domain ◽  
Coupled System ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Support Structures ◽  
Offshore Wind Turbines ◽  
Motion Responses ◽  
Sensitivity Studies ◽  
Jack Up

Monopiles are the most commonly used support structures for offshore wind turbines with up to 40m water depth due to the simplicity of the structure. The installation of turbine support structures can be carried out by a jack-up vessel which provides a stable working platform. However, the operational weather window using jack-up vessels is very limited due to the low sea states required for jacking up and down. Compared to jack-up installation vessels, floating vessels have more flexibility due to fast transportations between foundations. However, the vessel motions will affect the motion responses of the lifting objects, which might bring installation difficulties. Therefore, it is necessary to examine the dynamic responses of the coupled system to ensure safe offshore operations. In this paper, the installation operation of a monopile using a floating installation vessel is studied by a numerical model. Time domain simulations were carried out to study the installation process of a monopile, including lowering phase, landing phase and steady states after landing. Sensitivity studies were performed focusing on the effects by the gripper device stiffness and landing device stiffness. Comparisons of critical responses by using floating vessel and a jack-up vessel were also studied in the paper.

Model Experiment of a SPAR Type Offshore Wind Turbine in Storm Condition

2012 ◽  
Author(s):  
Kentaroh Kokubun ◽  
Shigesuke Ishida ◽  
Tadashi Nimura ◽  
Toshiki Chujo ◽  
Shigeo Yoshida ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Model Experiment ◽  
Wind Farms ◽  
Offshore Wind ◽  
Mooring Line ◽  
Offshore Wind Turbine ◽  
Ocean Engineering ◽  
Under Construction ◽  
Storm Condition ◽  
Sea Area

Wind power has the primary potential among renewable energies. Because Japan consists of little flat land and little shallow coast, floating wind turbine must be developed to make wind farms in Japan. Therefore, Japanese national demonstration project of Floating Offshore Wind Turbine (FOWT) was started in 2010FY by Ministry of the Environment and a SPAR-type FOWT is under construction at present. The floater is planned to be hybrid, consists of upper part by steal and lower part by pre-stressed concrete. Four fins are attached around the floater to suppress yaw motion. The floater is moored by three catenary chains. In order to confirm the safety of the FOWT in storm condition, experiments of a scale of 1/34.5 model were carried out at Ocean Engineering Basin of National Maritime Research Institute (NMRI), Japan. The draft of SPAR, the height of hub above sea level and the diameter of rotor of the model are 1.07m, 0.68m and 0.64m, respectively. In all experiments, blades are fixed to the hub under feathering condition and the hub is irrotational and fixed to the tower because this wind turbine is assumed to be under the storm condition, but wind blows transversely to the nacelle to give the maximum wind force. Water depth of the basin is smaller than the planned sea area on a reduced scale of model, therefore, springs and wires were used instead of chains in order to correspond to characteristics of horizontal mooring tension. Environmental forces are wind, wave and current in 50-year return period. Tensions of the 3 moorings and the motion of the model are measured in condition of wind and/or wave and/or current. Three kinds of direction of wind are adopted. One is the same direction as the wave and current, another is perpendicular to the wave and current, and the other is against to the wave and current. Besides the intact conditions a mooring-line-cut experiment in a storm condition was also conducted. Moreover, the effect of vortex induced motion (VIM), which occurs in current, was discussed. The results of the model experiment are reported to show the sufficient safety of this FOWT.

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