Identification of support structure damping of a full scale offshore wind turbine in normal operation

2015 ◽  
Vol 81 ◽  
pp. 882-895 ◽  
Author(s):  
Christina Koukoura ◽  
Anand Natarajan ◽  
Allan Vesth
Keyword(s):  
Wind Turbine ◽  
Full Scale ◽  
Offshore Wind ◽  
Normal Operation ◽  
Offshore Wind Turbine ◽  
Support Structure

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.

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.

Key Contributors to Lifetime Accumulated Fatigue Damage in an Offshore Wind Turbine Support Structure

2017 ◽  
Author(s):  
Emil Smilden ◽  
Erin E. Bachynski ◽  
Asgeir J. Sørensen
Keyword(s):  
Wind Turbine ◽  
Fatigue Damage ◽  
Control Strategies ◽  
Time Domain Analysis ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Wave Loads ◽  
Support Structure ◽  
Wear And Tear ◽  
Collateral Effects

A simulation study is performed to identify the key contributors to lifetime accumulated fatigue damage in the support-structure of a 10 MW offshore wind turbine placed on a monopile foundation in 30 m water depth. The relative contributions to fatigue damage from wind loads, wave loads, and wind/wave misalignment are investigated through time-domain analysis combined with long-term variations in environmental conditions. Results show that wave loads are the dominating cause of fatigue damage in the support structure, and that environmental condtions associated with misalignment angle > 45° are insignificant with regard to the lifetime accumulated fatigue damage. Further, the results are used to investigate the potential of event-based use of control strategies developed to reduce fatigue loads through active load mitigation. Investigations show that a large reduction in lifetime accumulated fatigue damage is possible, enabling load mitigation only in certain situations, thus limiting collateral effects such as increased power fluctuations, and wear and tear of pitch actuators and drive-train components.

Strength Assessment of Jacket Offshore Wind Turbine Support Structure Accounting for Rupture1

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Baran Yeter ◽  
Yordan Garbatov ◽  
C. Guedes Soares
Keyword(s):  
Wind Turbine ◽  
Low Cycle Fatigue ◽  
High Stress ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Small Scale ◽  
Support Structures ◽  
Support Structure ◽  
Strength Assessment ◽  
High Stress Concentration

The objective of the present work is to carry out the strength assessment of jacket offshore wind turbine support structures subjected to progressive rupture. A defect existing in a structure made during the fabrication may turn into a small-scale rupture and because of the high-stress concentration and low-cycle fatigue load. Therefore, the ultimate load-carrying capacity of the support structure is analyzed accounting for the progress of the rupture until the leg component experiences a full rupture along its circumference. The effect of imperfection severity is also investigated. The moment–curvature relationship of the structure concerning the studied cases is presented. Furthermore, the jacket support structures, at different water depths, are also analyzed and discussed. Finally, some of the leg components are removed one by one to study the redundancy of the jacket support structure at 80-m water depth.

Sign in / Sign up

Export Citation Format

Share Document