Effects of Blade Pitch, Rotor Yaw, and Wind–Wave Misalignment on a Large Offshore Wind Turbine Dynamics in Western Gulf of Mexico Shallow Water in 100-Year Return Hurricane

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Ling Ling Yin ◽  
King Him Lo ◽  
Su Su Wang
Keyword(s):  
Gulf Of Mexico ◽  
Wind Turbine ◽  
Shallow Water ◽  
Structural Dynamics ◽  
Structural Design ◽  
Wind Wave ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Deep Insight ◽  
Support Structure

To determine the optimal park configuration of a large offshore turbine in a hurricane, a study is conducted on effects of blade pitch and rotor yaw, and wind–wave misalignment, in a 100-year return hurricane on a 13.2-MW large offshore wind turbine (OWT) in western Gulf of Mexico (GOM) shallow water. The OWT structure considered includes a rotor with three 100-m long blades and a monotower support structure. Maximum loads on the wind turbine are determined with blade pitch and rotor yaw, with and without wind–wave misalignment in the 100-year return hurricane. The results show that effects of blade pitch and rotor yaw on turbine structural dynamics are significant, whereas the effect of wind–wave misalignment is small in the context of structural design in strength. The study provides deep insight to wind turbine dynamics and its structural design in the extreme hurricane.

Structural Dynamics and Load Analysis of Large Offshore Wind Turbines in Western Gulf of Mexico Shallow Water

2014 ◽  
Author(s):  
Ling Ling Yin ◽  
King Him Lo ◽  
Su Su Wang
Keyword(s):  
Gulf Of Mexico ◽  
Wind Turbine ◽  
Shallow Water ◽  
Structural Dynamics ◽  
Natural Frequencies ◽  
Offshore Wind ◽  
Normal Operation ◽  
Mode Shapes ◽  
Offshore Wind Turbine ◽  
Support Structure

In this paper, a study is conducted on wind and metocean loads and associated structural dynamics of a 13.2-MW large offshore wind turbine in Western Gulf of Mexico (GOM) shallow water. The offshore wind turbine considered includes a rotor with three 100-meter long blades and a mono-tower support structure. Natural frequencies and mode shapes of the blades and the mono-tower are determined first and used subsequently to establish a Campbell diagram for safe wind turbine operation. The results show that hydrodynamic added mass has little effect on the natural frequencies and mode shapes of the support structure but it introduces, in part, appreciable effects on loads carried by the turbine when the blades are pitched at wind speeds above the rated speed. Also determined, for normal operation and extreme metocean conditions (i.e., 100-year return hurricanes), are normal thrust on the wind rotor, blade-tip displacement, overturning moment and tower-top displacement sustained by the wind turbine.

Effect of Pile-Soil Interaction on Structural Dynamics of Large MW Scale Offshore Wind Turbines in Shallow-Water Western GOM

2015 ◽  
Author(s):  
Ling Ling Yin ◽  
King Him Lo ◽  
Su Su Wang
Keyword(s):  
Wind Turbine ◽  
Shallow Water ◽  
Structural Dynamics ◽  
Turbine Rotor ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Support Structure ◽  
Tower Structure ◽  
Spring System ◽  
Different Soils

The effect of pile-soil interaction on structural dynamics is investigated for a large offshore wind turbine in the hurricane-prone Western Gulf of Mexico (GOM) shallow water. The offshore wind turbine has a rotor with three 100-meter blades and a mono-tower structure. Loads on the turbine rotor and the support structure subject to a 100-year return hurricane are determined. Several types of soil are considered and modeled with a distributed spring system. The results reveal that pile-soil interaction affects dynamics of the turbine support structure significantly, but not the wind rotor dynamics. Designed with proper pile lengths, natural frequencies of the turbine structure in different soils stay outside dominant frequencies of wave energy spectra in both normal operating and hurricane sea states, but stay between blade passing frequency intervals. Hence potential resonance of the turbine support structure is not of concern. A comprehensive Campbell diagram is constructed for safe operation of the offshore turbine in different soils.

Effect of Pile–Soil Interaction on Structural Dynamics of Large Moment Magnitude-Scale Offshore Wind Turbines in Shallow-Water Western Gulf of Mexico

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Ling Ling Yin ◽  
King Him Lo ◽  
Su Su Wang
Keyword(s):  
Gulf Of Mexico ◽  
Shallow Water ◽  
Structural Dynamics ◽  
Turbine Rotor ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Support Structure ◽  
Offshore Wind Turbines ◽  
Spring System ◽  
Different Soils

The effect of pile–soil interaction on structural dynamics is investigated for a large offshore wind turbine (OWT) in the hurricane-prone Western Gulf of Mexico (GOM) shallow water. The OWT has a rotor with three 100-meter blades and a monotower structure. Loads on the turbine rotor and the support structure subject to a 100-year return hurricane are determined. Several types of soil are considered and modeled with a distributed spring system. The results reveal that pile–soil interaction affects dynamics of the turbine support structure significantly, but not the rotor dynamics. Designed with proper pile lengths, natural frequencies of the turbine structure in different soils stay outside dominant frequencies of wave energy spectra in both normal operating and hurricane sea states, but stay between blade passing frequency intervals. Hence, potential resonance of the turbine support structure is not of concern. A comprehensive Campbell diagram is constructed for safe operation of the offshore turbine in different soils.

Model Test and Numerical Analysis of an Offshore Bottom Fixed Pentapod Wind Turbine Under Seismic Loads

2016 ◽  
Author(s):  
Wenhua Wang ◽  
Zhen Gao ◽  
Xin Li ◽  
Torgeir Moan ◽  
Bin Wang
Keyword(s):  
Wind Turbine ◽  
Wind Wave ◽  
Seismic Analysis ◽  
Wind Farms ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Test Model ◽  
Structural Dynamic ◽  
Load Conditions

In the last decade the wind energy industry has developed rapidly in China, especially offshore. For a water depth less than 20m, monopile and multi-pile substructures (tripod, pentapod) are applied widely in offshore wind farms. Some wind farms in China are located in high seismicity regions, thus, the earthquake load may become the dominant load for offshore wind turbines. This paper deals with the seismic behavior of an offshore wind turbine (OWT) consisting of the NREL 5MW baseline wind turbine, a pentapod substructure and a pile foundation of a real offshore wind turbine in China. A test model of the OWT is designed based on the hydro-elastic similarity. Test cases of different load combinations are performed with the environmental conditions generated by the Joint Earthquake, Wave and Current Simulation System and the Simple Wind Field Generation System at Dalian University of Technology, China, in order to investigate the structural dynamic responses under different load conditions. In the tests, a circular disk is used to model the rotor-nacelle system, and a force gauge is fixed at the center of the disk to measure the wind forces during the tests. A series of accelerometers are arranged along the model tower and the pentapod piles, and strain gauges glued on the substructure members are intended to measure the structural dynamic responses. A finite element model of the complete wind turbine is also established in order to compare the theoretical results with the test data. The hydro-elastic similarity is validated based on the comparison of the measured dynamic characteristics and the results of the prototype modal analysis. The numerical results agree well with the experimental data. Based on the comparisons of the results, the effect of the wind and sea loads on the structural responses subjected to seismic is demonstrated, especially the influence on the global response of the structure. It is seen that the effect of the combined seismic, wind, wave and current load conditions can not be simply superimposed. Hence the interaction effect in the seismic analysis should be considered when the wind, wave and current loads have a non-negligible effect.

Monitoring Changes in the Soil and Foundation Characteristics of an Offshore Wind Turbine Using Automated Operational Modal Analysis

2013 ◽  
Vol 569-570 ◽  
pp. 652-659 ◽  
Author(s):  
Gert de Sitter ◽  
Wout Weitjens ◽  
Mahmoud El-Kafafy ◽  
Christof Devriendt
Keyword(s):  
Wind Turbine ◽  
Modal Analysis ◽  
Continuous Monitoring ◽  
Low Frequency ◽  
Operational Modal Analysis ◽  
Human Interaction ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Support Structure ◽  
Lower Natural Frequency

This paper will show the first results of a long term monitoring campaign on an offshore wind turbine in the Belgian North Sea. It will focus on the vibration levels and resonant frequencies of the fundamental modes of the support structure. These parameters will be crucial to minimize O&M costs and to extend the lifetime of offshore wind turbine structures. For monopile foundations for example, scouring and reduction in foundation integrity over time are especially problematic because they reduce the fundamental structural resonance of the support structure, aligning that resonance frequency more closely to the lower frequencies. Since both the broadband wave energy and the rotating frequency of the turbine are contained in this low frequency band, the lower natural frequency can create resonant behavior increasing fatigue damage. Continuous monitoring of the effect of scour on the dynamics of the wind turbine will help to optimize the maintenance activities on the scour protection system. To allow a proper continuous monitoring during operation, reliable state-of-the-art operational modal analysis techniques should be used and these are presented in this paper. The methods are also automated, so that no human-interaction is required and the system can track the natural frequencies and damping ratios in a reliable manner.

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