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.

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.

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.

A Consistent Structural Damping Model for Integrated and Superelement Modelling of Offshore Wind Turbine Support Structures in Wind Turbine Design Software Bladed

2019 ◽  
Author(s):  
William Collier
Keyword(s):  
Wind Turbine ◽  
Offshore Wind ◽  
Integrated Modelling ◽  
Mode Shapes ◽  
Offshore Wind Turbine ◽  
Natural Mode ◽  
Structural Damping ◽  
Support Structure ◽  
Modal Damping ◽  
Modelling Approaches

Abstract In aero-elastic simulation of offshore wind turbines, the support structure can be modelled using an “integrated” approach, where the jacket and tower and modelled explicitly as one structural body, or a “superelement” approach, where the jacket part of the support structure is included as a superelement. For integrated modelling, vibration mode shapes are calculated for the whole support structure. For a superelement approach, separate mode shapes are defined for superelement and the tower. The different modal basis makes it difficult to align the structural damping definition for the two approaches, meaning that manual tuning of the modal damping ratios has previously been necessary to achieve equivalent damping on the whole support structure for the two approaches. To provide a consistent damping approach, it is proposed to specify modal damping ratios or Rayleigh damping on a modal basis which is common to the two approaches: the support structure natural mode shapes. When damping is specified on the natural modes of the support structure, equivalent support structure damping is observed for superelement and integrated modelling approaches. This allows the target support structure damping ratios to be achieved easily and also facilitates studies to compare the superelement and integrated modelling approaches.

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.

scholarly journals Full field assessment of wind turbine near wake deviation in relation to yaw misalignment

2016 ◽  
Author(s):  
Juan-José Trujillo ◽  
Janna K. Seifert ◽  
Ines Würth ◽  
David Schlipf ◽  
Martin Kühn
Keyword(s):  
Wind Turbine ◽  
Tip Vortex ◽  
Offshore Wind ◽  
Normal Operation ◽  
Offshore Wind Turbine ◽  
Near Wake ◽  
Thrust Coefficient ◽  
Full Field ◽  
Wake Field ◽  
Partial Load

Abstract. Presently there is a lack of data revealing the behaviour of the path followed by the near wake of full scale wind turbines and its dependence on yaw misalignment. Here we present an experimental analysis of the horizontal wake deviation of a 5 MW offshore wind turbine between 0.6 and 1.4 diameters downstream. The wake field has been scanned with a short range lidar and the wake path has been reconstructed by means of two-dimensional Gaussian tracking. We analysed the measurements for rotor yaw misalignments arising in normal operation and during partial load, representing high thrust coefficient conditions. We classified distinctive wake paths with reference to yaw misalignment, based on the nacelle wind vane, in steps of 3° in a range of ±10.5°. All paths observed in the nacelle frame of reference showed a consistent convergence towards 0.9 rotor diameters downstream suggesting a kind of wake deviation delay. This contrasts with published results from wind tunnels which in general report a convergence towards the rotor. The discrepancy is evidenced in particular in a comparison which we performed against published paths obtained by means of tip vortex tracking.

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