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.

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.

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.

Design Requirements for Floating Offshore Wind Turbines

2013 ◽  
Author(s):  
Xiaohong Chen ◽  
Qing Yu
Keyword(s):  
Wind Turbine ◽  
Case Studies ◽  
Wind Turbines ◽  
Offshore Wind ◽  
Design Parameters ◽  
Offshore Wind Turbine ◽  
Support Structure ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Design Requirements

This paper presents the research in support of the development of design requirements for floating offshore wind turbines (FOWTs). An overview of technical challenges in the design of FOWTs is discussed, followed by a summary of the case studies using representative FOWT concepts. Three design concepts, including a Spar-type, a TLP-type and a Semisubmersible-type floating support structure carrying a 5-MW offshore wind turbine, are selected for the case studies. Both operational and extreme storm conditions on the US Outer Continental Shelf (OCS) are considered. A state-of-the-art simulation technique is employed to perform fully coupled aero-hydro-servo-elastic analysis using the integrated FOWT model. This technique can take into account dynamic interactions among the turbine Rotor-Nacelle Assembly (RNA), turbine control system, floating support structure and stationkeeping system. The relative importance of various design parameters and their impact on the development of design criteria are evaluated through parametric analyses. The paper also introduces the design requirements put forward in the recently published ABS Guide for Building and Classing Floating Offshore Wind Turbine Installations (ABS, 2013).

Bottom Supported Tension Leg Tower for Offshore Wind Turbines

2017 ◽  
Author(s):  
Arunjyoti Sarkar ◽  
Ove Tobias Gudmestad
Keyword(s):  
Shallow Water ◽  
Water Depth ◽  
High Energy ◽  
Offshore Wind ◽  
High Energy Density ◽  
Support Structure ◽  
Application Range ◽  
Offshore Wind Turbines ◽  
Almost All ◽  
Near Future

Power production from the high energy density offshore wind has now emerged as a potential source of renewable energy for the future of mankind. While the installed global cumulative offshore wind capacity in 2014 was around 8 GW [1], almost all of this came from the shallow water sites (water depths equal to 25m or less) where typical bottom founded structures (such as: monopole, jacket, concrete gravity type, etc.) are used to support the turbines. Today, most of the shallow water sites are exhausted, and the industry is looking for setting up turbines at the deeper water sites, where the existing bottom founded structures tend to become massive and expensive. On the other hand, the floating wind turbine concept, apart from being expensive, is more suitable for water depth of 100 m or more. It is expected that in the near future, the industry will primarily focus on concepts that may extend the application range of the existing bottom founded structures towards the deeper waters. In this paper, a novel support structure concept termed “Bottom supported tension leg tower” is presented, and its preliminary technical feasibility is checked for a monopile type structure for 50 m water depth. The concept can also be used with a jacket or a gravity type support structure. The potential of using the monopile based structure at 100m water depth is also briefly addressed.

Modeling Nonlinear Irregular Waves in Reliability Studies for Offshore Wind Turbines

2009 ◽  
Author(s):  
P. Agarwal ◽  
L. Manuel
Keyword(s):  
Wind Turbines ◽  
Offshore Wind ◽  
Irregular Waves ◽  
Offshore Wind Turbine ◽  
Shallow Waters ◽  
Support Structure ◽  
Offshore Wind Turbines ◽  
Linear And Nonlinear ◽  
Wave Models

While addressing different load cases according to the IEC guidelines for offshore wind turbines, designers are required to estimate long-term extreme and fatigue loads; this is usually done by carrying out time-domain stochastic turbine response simulations. This involves simulation of the stochastic inflow wind field on the rotor plane, of irregular (random) waves on the support structure, and of the turbine response. Obtaining realistic response of the turbine depends, among other factors, on appropriate modeling of the incident wind and waves. The current practice for modeling waves on offshore wind turbines is limited to the representation of linear irregular waves. While such models are appropriate for deep waters, they are not accurate representations of waves in shallow waters where offshore wind turbines are most commonly sited. In shallow waters, waves are generally nonlinear in nature. It is, therefore, of interest to assess the influence of alternative wave models on the behavior of wind turbines (e.g., on the tower response) as well as on extrapolated long-term turbine loads. The expectation is that nonlinear (second-order) irregular waves can better describe waves in shallow waters. In this study, we investigate differences in turbine response statistics and in long-term load predictions that arise from the use of alternative wave models. We compute loads on the monopile support structure of a 5MW offshore wind turbine model for several representative environmental states where we focus on differences in estimates of the extreme tower bending moment at the mudline due to linear and nonlinear waves. Finally, we compare long-term load predictions using inverse reliability procedures with both the linear and nonlinear wave models. We present convergence criteria that may be used to establish accurate 20-year loads and discuss comparative influences of wind versus waves in long-term load prediction.

scholarly journals Performance and Effect of Load Mitigation of a Trailing-Edge Flap in a Large-Scale Offshore Wind Turbine

2020 ◽  
Vol 8 (2) ◽  
pp. 72 ◽  
Author(s):  
Xin Cai ◽  
Yazhou Wang ◽  
Bofeng Xu ◽  
Junheng Feng
Keyword(s):  
Wind Turbine ◽  
Load Distribution ◽  
Large Scale ◽  
Turbine Rotor ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Trailing Edge ◽  
Turbulent Wind ◽  
Offshore Wind Turbines ◽  
Trailing Edge Flap

As a result of the large-scale trend of offshore wind turbines, wind shear and turbulent wind conditions cause significant fluctuations of the wind turbine’s torque and thrust, which significantly affect the service life of the wind turbine gearbox and the power output stability. The use of a trailing-edge flap is proposed as a supplement to the pitch control to mitigate the load fluctuations of large-scale offshore wind turbines. A wind turbine rotor model with a trailing-edge flap is established by using the free vortex wake (FVW) model. The effects of the deflection angle of the trailing-edge flap on the load distribution of the blades and wake flow field of the offshore wind turbine are analyzed. The wind turbine load response under the control of the trailing-edge flap is obtained by simulating shear wind and turbulent wind conditions. The results show that a better control effect can be achieved in the high wind speed condition because the average angle of attack of the blade profile is small. The trailing-edge flap significantly changes the load distribution of the blade and the wake field and mitigates the low-frequency torque and thrust fluctuations of the turbine rotor under the action of wind shear and turbulent wind.

Reliability Assessment of Fatigue Critical Welded Details in Wind Turbine Jacket Support Structures

2013 ◽  
Author(s):  
Kim Branner ◽  
Henrik Stensgaard Toft ◽  
Philipp Haselbach ◽  
Anand Natarajan ◽  
John D. Sørensen
Keyword(s):  
Structural Dynamics ◽  
Probabilistic Approach ◽  
Reliability Assessment ◽  
Offshore Wind ◽  
Support Structures ◽  
Support Structure ◽  
Operational Conditions ◽  
Offshore Wind Turbines ◽  
Stress Cycles ◽  
The Individual

This paper describes a probabilistic approach to reliability assessment of fatigue critical welded details in jacket support structures for offshore wind turbines. The analysis of the jacket response to the operational loads is performed using Finite Element Method (FEM) simulations in SIMULIA Abaqus. Fatigue stress cycles are computed on the jacket members by applying tower top loads from an aeroelastic simulation with superimposed marine loads and in accordance to the IEC-61400-3 guidelines for operational conditions. The combined effect of the hydrodynamic loads and the rotor loads on the jacket structure is analyzed in a de-coupled scheme, but including the structural dynamics of the support structure. The failure prediction of the welded joints, connecting the individual members of the support structure is based on SN-curves and Miners rule according to ISO 19902 and DNV-RP-C203/DNV-OS-J101. Probabilistic SN-curves and a stochastic model for Miners rule is used to estimate the reliability of selected critical welded details in the jacket structure taken into account the uncertainty in the fatigue stresses.

scholarly journals Maintenance Planning of Offshore Wind Turbine Using Condition Monitoring Information

2009 ◽  
Author(s):  
Jose´ G. Rangel-Rami´rez ◽  
John D. So̸rensen
Keyword(s):  
Condition Monitoring ◽  
Wind Turbines ◽  
Wind Farm ◽  
Offshore Structures ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Maintenance Planning ◽  
Offshore Wind Turbines ◽  
Inspection And Maintenance ◽  
Monitoring Information

Deterioration processes such as fatigue and corrosion are typically affecting offshore structures. To “control” this deterioration, inspection and maintenance activities are developed. Probabilistic methodologies represent an important tool to identify the suitable strategy to inspect and control the deterioration in structures such as offshore wind turbines (OWT). Besides these methods, the integration of condition monitoring information (CMI) can optimize the mitigation activities as an updating tool. In this paper, a framework for risk-based inspection and maintenance planning (RBI) is applied for OWT incorporating CMI, addressing this analysis to fatigue prone details in welded steel joints at jacket or tripod steel support structures for offshore wind turbines. The increase of turbulence in wind farms is taken into account by using a code-based turbulence model. Further, additional modes t integrate CMI in the RBI approach for optimal planning of inspection and maintenance. As part of the results, the life cycle reliabilities and inspection times are calculated, showing that earlier inspections are needed at in-wind farm sites. This is expected due to the wake turbulence increasing the wind load. With the integration of CMI by means Bayesian inference, a slightly change of first inspection times are coming up, influenced by the reduction of the uncertainty and harsher or milder external agents.

scholarly journals Improving the Strategy of Maintaining Offshore Wind Turbines through Petri Net Modelling

2021 ◽  
Vol 11 (2) ◽  
pp. 574
Author(s):  
Rundong Yan ◽  
Sarah Dunnett
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Petri Net ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Maintenance Costs ◽  
Offshore Wind Turbines ◽  
Major Repair ◽  
Wind Turbine System ◽  
Periodic Maintenance

In order to improve the operation and maintenance (O&M) of offshore wind turbines, a new Petri net (PN)-based offshore wind turbine maintenance model is developed in this paper to simulate the O&M activities in an offshore wind farm. With the aid of the PN model developed, three new potential wind turbine maintenance strategies are studied. They are (1) carrying out periodic maintenance of the wind turbine components at different frequencies according to their specific reliability features; (2) conducting a full inspection of the entire wind turbine system following a major repair; and (3) equipping the wind turbine with a condition monitoring system (CMS) that has powerful fault detection capability. From the research results, it is found that periodic maintenance is essential, but in order to ensure that the turbine is operated economically, this maintenance needs to be carried out at an optimal frequency. Conducting a full inspection of the entire wind turbine system following a major repair enables efficient utilisation of the maintenance resources. If periodic maintenance is performed infrequently, this measure leads to less unexpected shutdowns, lower downtime, and lower maintenance costs. It has been shown that to install the wind turbine with a CMS is helpful to relieve the burden of periodic maintenance. Moreover, the higher the quality of the CMS, the more the downtime and maintenance costs can be reduced. However, the cost of the CMS needs to be considered, as a high cost may make the operation of the offshore wind turbine uneconomical.

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