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.

Assessment of Allowable Sea States During Installation of Offshore Wind Turbine Monopiles With Shallow Penetration in the Seabed

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Lin Li ◽  
Wilson Guachamin Acero ◽  
Zhen Gao ◽  
Torgeir Moan
Keyword(s):  
Time Domain ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Offshore Wind Turbines ◽  
Heavy Lift ◽  
Characteristic Values ◽  
Limiting Parameters ◽  
The Time Domain ◽  
Penetration Depths

Installation of offshore wind turbines (OWTs) requires careful planning to reduce costs and minimize associated risks. The purpose of this paper is to present a method for assessing the allowable sea states for the initial hammering process (shallow penetrations in the seabed) of a monopile (MP) using a heavy lift floating vessel (HLV) for use in the planning of the operation. This method combines the commonly used installation procedure and the time-domain simulations of the sequential installation activities. The purpose of the time-domain simulation is to quantitatively study the system dynamic responses to identify critical events that may jeopardize the installation and the corresponding limiting response parameters. Based on the allowable limits and the characteristic values of the limiting response parameters, a methodology to find the allowable sea states is proposed. Case studies are presented to show the application of the methodology. The numerical model of the dynamic HLV–MP system includes the coupling between HLV and MP via a gripper device, and soil–MP interaction at different MP penetration depths. It is found that the limiting parameters are the gripper force and the inclination of the MP. The systematic approach proposed herein is general and applies to other marine operations.

PyraWind™: An Innovative Floating Offshore Wind Turbine (FOWT) Global Performance Analysis

2021 ◽  
Author(s):  
Zhiyong Yang ◽  
Xiaoqiang Bian ◽  
Yu Shi
Keyword(s):  
Wind Turbine ◽  
Hydrodynamic Model ◽  
Coupled System ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Floating Offshore Wind Turbine ◽  
Offshore Wind Turbines ◽  
Ongoing Work ◽  
Heavy Lift ◽  
Solid Foundation

Abstract In the near future, the offshore wind industry will experience a significant increase of turbine size and of floating wind development activities. A floating offshore wind turbine foundation offers many advantages, such as flexibility in site selection, access to better offshore wind resources, and quayside integration to avoid a costly heavy lift vessel offshore campaign. PyraWind™ is a patented three canted column semisubmersible floating foundation for ultra large offshore wind turbines. It is designed to accommodate a wind turbine, 14 MW or larger, in the center of the interconnected columns of the hull with minimal modifications to the tower, nacelle and turbine. The pyramid-shaped hull provides a stable, solid foundation for the large wind turbine under development. This paper summarizes the feasibility study conducted for the PyraWind™ concept. The design basis for wind turbine floating foundations is described and the regulatory requirements are discussed. Also included are the hydrodynamic analysis of the hull and ongoing work consisting of coupling hull hydrodynamics with wind-turbine aerodynamic loads. The fully coupled system was analyzed using OpenFAST, an aerodynamic software package for wind turbine analysis with the ability to be coupled with the hydrodynamic model. Due to the canted columns, a nonlinear analysis was performed using the coupled numerical hydrodynamic model of the platform with mooring system in extreme sea states.

Dynamic Responses of a Spar Type Floating Offshore Wind Turbine With Failed Moorings

2020 ◽  
Author(s):  
Yajun Ren ◽  
Vengatesan Venugopal
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Mooring System ◽  
Floating Offshore Wind Turbine ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Platform Motions

Abstract The complex dynamic characteristics of Floating Offshore Wind Turbines (FOWTs) have raised wider consideration, as they are likely to experience harsher environments and higher instabilities than the bottom fixed offshore wind turbines. Safer design of a mooring system is critical for floating offshore wind turbine structures for station keeping. Failure of mooring lines may lead to further destruction, such as significant changes to the platform’s location and possible collisions with a neighbouring platform and eventually complete loss of the turbine structure may occur. The present study focuses on the dynamic responses of the National Renewable Energy Laboratory (NREL)’s OC3-Hywind spar type floating platform with a NREL offshore 5-MW baseline wind turbine under failed mooring conditions using the fully coupled numerical simulation tool FAST. The platform motions in surge, heave and pitch under multiple scenarios are calculated in time-domain. The results describing the FOWT motions in the form of response amplitude operators (RAOs) and spectral densities are presented and discussed in detail. The results indicate that the loss of the mooring system firstly leads to longdistance drift and changes in platform motions. The natural frequencies and the energy contents of the platform motion, the RAOs of the floating structures are affected by the mooring failure to different degrees.

Challenges in the Design of an Offshore Wind Turbine Foundation for Arctic Conditions

2002 ◽  
Author(s):  
Alistair E. Gill ◽  
Ramsay Fraser
Keyword(s):  
Fatigue Life ◽  
Sea Ice ◽  
Time Domain ◽  
Deep Layer ◽  
Life Time ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Offshore Wind Turbines ◽  
Arctic Conditions ◽  
Ice Loads

NEG Micon’s Yttre Stengrund Offshore Wind Turbines in the Kalmarsund, Sweden, are supported on unique foundations designed by AMEC. The chosen foundation comprised a steel monopile secured into a rock socket drilled out beneath a deep layer of overlying soil. Sea-ice loading and fatigue governed the design. To minimise the sea-ice loads the foundation was fitted with an ice protection shield. In order to achieve the required fatigue life, time domain simulations were conducted to determine the response of the turbine to combined wind and wave action. Details of the fatigue analyses and methods used to calculate the sea-ice loading are presented herein.

A Fast and Practical Method for Predicting the Fatigue Life of Offshore Wind Turbine Jacket Support Structures

2017 ◽  
Author(s):  
Chaoshuai Han ◽  
Yongliang Ma ◽  
Xianqiang Qu ◽  
Peijiang Qin ◽  
Binbin Qiu
Keyword(s):  
Fatigue Life ◽  
Wind Turbine ◽  
Fatigue Damage ◽  
Time Domain ◽  
Practical Method ◽  
Computational Effort ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Wave Loads ◽  
Support Structures

Fatigue assessment is a very important part in the design process of offshore wind turbine support structures subjected to wind and wave loads. Fully coupled time domain simulations due to wind and wave loads can potentially provide reliable fatigue predictions, however, it will take high computational effort to carry out fatigue analysis of the simultaneous wind and wave response of the support structure in time domain. For convenience and reducing computational efforts, a fast and practical method is proposed for predicting the fatigue life of offshore wind turbine jacket support structures. Wind induced fatigue is calculated in the time domain using ANSYS based on rainflow counting, and wave induced fatigue is computed in frequency domain using SACS based on a linear spectral analysis. Fatigue damage of X-joints and K-joints under combined environmental loads of wind and wave is estimated by using the proposed method. To verify the accuracy of the proposed formula, fatigue damage based on time domain rainflow cycle counting is calculated and can be considered as a reference. It is concluded that the proposed method provides reasonable fatigue damage predictions and can be adopted for evaluating the combined fatigue damage due to wind and wave loads in offshore wind turbine.

Response Analysis of a Nonstationary Lowering Operation for an Offshore Wind Turbine Monopile Substructure

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Lin Li ◽  
Zhen Gao ◽  
Torgeir Moan
Keyword(s):  
Wind Turbine ◽  
Time Domain ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Irregular Waves ◽  
Offshore Wind Turbine ◽  
Response Analysis ◽  
Steady State Condition ◽  
Strip Theory ◽  
Lifting System

This study addresses numerical modeling and time-domain simulations of the lowering operation for installation of an offshore wind turbine monopile (MP) with a diameter of 5.7 m and examines the nonstationary dynamic responses of the lifting system in irregular waves. Due to the time-varying properties of the system and the resulting nonstationary dynamic responses, numerical simulation of the entire lowering process is challenging to model. For slender structures, strip theory is usually applied to calculate the excitation forces based on Morison's formula with changing draft. However, this method neglects the potential damping of the structure and may overestimate the responses even in relatively long waves. Correct damping is particularly important for the resonance motions of the lifting system. On the other hand, although the traditional panel method takes care of the diffraction and radiation, it is based on steady-state condition and is not valid in the nonstationary situation, as in this case in which the monopile is lowered continuously. Therefore, this paper has two objectives. The first objective is to examine the importance of the diffraction and radiation of the monopile in the current lifting model. The second objective is to develop a new approach to address this behavior more accurately. Based on the strip theory and Morison's formula, the proposed method accounts for the radiation damping of the structure during the lowering process in the time-domain. Comparative studies between different methods are presented, and the differences in response using two types of installation vessel in the numerical model are also investigated.

scholarly journals Dynamic Response of Articulated Offshore Wind Turbines under Different Water Depths

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2784
Author(s):  
Pei Zhang ◽  
Shugeng Yang ◽  
Yan Li ◽  
Jiayang Gu ◽  
Zhiqiang Hu ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Dynamic Responses ◽  
Wind Pressure ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Offshore Area ◽  
Offshore Wind Turbines ◽  
Water Depths

Focusing on the transitional depth offshore area from 50 m to 75 m, types of articulated foundations are proposed for supporting the NREL 5 MW offshore wind turbine. To investigate the dynamic behaviors under various water depths, three articulated foundations were adopted and numerical simulations were conducted in the time domain. An in-house code was chosen to simulate the dynamic response of the articulated offshore wind turbine. The aerodynamic load on rotating blades and the wind pressure load on tower are calculated based on the blade element momentum theory and the empirical formula, respectively. The hydrodynamic load is simulated by 3D potential flow theory. The motions of foundation, the aerodynamic performance of the wind turbine, and the loads on the articulated joint are documented and compared in different cases. According to the simulation, all three articulated offshore wind turbines show great dynamic performance and totally meet the requirement of power generation under the rated operational condition. Moreover, the comparison is based on time histories and spectra among these responses. The result shows that dynamic responses of the shallower one oscillate more severely compared to the other designs.

scholarly journals Investigation of Hydrodynamic Forces for Floating Offshore Wind Turbines on Spar Buoys and Tension Leg Platforms with the Mooring Systems in Waves

2019 ◽  
Vol 9 (3) ◽  
pp. 608 ◽  
Author(s):  
Yu-Hsien Lin ◽  
Shin-Hung Kao ◽  
Cheng-Hao Yang
Keyword(s):  
Wind Turbines ◽  
Time Domain ◽  
Simulation System ◽  
Offshore Wind ◽  
Modular System ◽  
Mooring System ◽  
Mooring Lines ◽  
Offshore Wind Turbines ◽  
Motion Responses ◽  
Floating Offshore Wind Turbines

This study aims to develop a modularized simulation system to estimate dynamic responses of floating Offshore Wind Turbines (OWTs) based on the concepts of spar buoy and Tension Leg Platform (TLP) corresponding with two typical mooring lines. The modular system consists of the hydrodynamic simulator based the Cummins time domain equation, the Boundary Element Method (BEM) solver based on the 3D source distribution method, and an open-source visualization software ParaView to analyze the interaction between floating OWTs and waves. In order to realize the effects of mooring loads on the floating OWTs, the stiffness and damping matrices are applied to the quasi-static mooring system. The Response Amplitude Operators (RAOs) are compared between our predicted results and other published data to verify the modularized simulation system and understand the influence of mooring load on the motion responses in regular or irregular waves. It is also demonstrated that the quasi-static mooring system is applicable to different types of mooring lines as well as determining real-time motion responses. Eventually, wave load components at the resonance frequencies of different motion modes for selected floating OWTs would be present in the time domain.

Performance Research on Tension Leg Platform of Floating Offshore Wind Turbine

2013 ◽  
Vol 724-725 ◽  
pp. 645-648
Author(s):  
Yue Wen Gao ◽  
Chun Li ◽  
Xin Cheng
Keyword(s):  
Wind Turbine ◽  
Time Domain ◽  
Reference Value ◽  
Wave Force ◽  
Offshore Wind ◽  
Maximum Response ◽  
Offshore Wind Turbine ◽  
Tension Leg Platform ◽  
Motion Response ◽  
Motion Responses

Platform structure is the basic guarantee for safety operation of offshore wind turbine. Based on the boundary element method and combined with multi-body dynamics, analyzing motion response and wave force mechanism to the platform structure, and obtained the dynamic response and the wave force change of the platform structures in time domain, last analyzes the motion response and wave force change of tension leg platform in surge, sway and heave also roll, pitch and yaw direction. The results show that the maximum response of sway and the minimum response of surge have the same direction, it is the same with the maximum response of pitch and the minimum response of roll ; Motion responses of heave and yaw change not as acutely as other four directions ; In time-domain variation range, motion response of surge, heave and pitch change acutely, while motion responses of sway, roll and yaw change slightly. Wave force focus mostly in heave and pitch direction. The results is high reference value on offshore tension leg platform structural design and optimization.

Radiative Damping of Offshore Wind Turbine Gravity Base Foundations at Low Frequencies

2016 ◽  
Author(s):  
Rui He ◽  
Ting Huang
Keyword(s):  
Wind Turbines ◽  
Clean Energy ◽  
The Other ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Low Frequencies ◽  
Offshore Wind Turbines ◽  
Dynamic Loadings ◽  
Radiative Damping

With the fast increasing need of clean energy, more and more offshore wind turbines (OWTs) are being planned or constructed. Some offshore wind turbines are supported on Gravity Base Foundations (GBFs). As tall and slender offshore wind turbines are very sensitivity to the dynamic loadings at low frequencies, if designed improperly, it is likely to cause resonances. On the other hand, most of the designs ignore the radiative damping of GBFs, which will lead to a conservative solution and a cost of more money. In this paper, by referring to three different models, the corresponding vertical, horizontal and rocking damping ratios for a typical GBF at low frequencies are obtained and compared, respectively. With these damping ratios obtained, one can develop a more realistic and economic model to calculate the dynamic responses of offshore wind turbines on GBFs under both vertical and horizontal forces at low frequencies.

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