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Probabilistic Response and Short-Term Extreme Load Estimation of offshore Monopile wind turbine Towers by Probability Density Evolution Method

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China Ocean Engineering 2022年第3期36卷 363-371页

作者： ZHANG Hui XU Ya-zhou School of Building Services Science and Engineering Xi’an University of Architecture and TechnologyXi’an 710055China School of Civil Engineering Xi’an University of Architecture and TechnologyXi’an 710055China

A new analysis framework based on probability density evolution method(PDEM)and its Chebyshev collocation solution are introduced to predict the dynamic response and short-term extreme load of offshore wind turbine(OWT)towers subjected to random sea state.With regard to the stochastic responses,random function method is employed to generate samples of sea elevation,the probability density evolution equation(PDEE)is solved to calculate time-variant probability density functions of structural responses.For the probabilistic load estimation,a FAST model of NREL 5MW offshore turbine is established to obtain samples of bending moment at the tower base.The equivalent extreme event theory is used to construct a virtual stochastic process(VSP)to assess the short-term extreme load.The results indicate that the proposed approach can predict time-variant probability density functions of the structural responses,and shows good agreement with Monte Carlo simulations.Additionally,the predicted short-term extreme load can capture the fluctuation at the tail of the extreme value distribution,thus is more rational than results from the typical distribution models.Overall,the proposed method shows good adaptation,precision and efficiency for the dynamic response analysis and load estimation of OWT towers.

关键词： offshore wind turbine probability density evolution method Chebyshev collocation matrix exponential Monte Carlo

Numerical Simulation of Icing on Nrel 5-MW Reference offshore wind turbine Blades Under Different Icing Conditions

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China Ocean Engineering 2022年第5期36卷 767-780页

作者： CAO Hui-qing BAI Xu MA Xian-dong YIN Qun YANG Xiang-yu School of Naval Architecture&Ocean Engineering Jiangsu University of Science and TechnologyZhenjiang 212003China The Department of Engineering Lancaster UniversityLancaster LA14YWUK

offshore wind energy resources are operational in cold regions,while offshore wind turbines will face the threat of icing.Therefore,it is necessary to study icing of offshore wind turbines under different icing conditions.In this study,icing sensitivity of offshore wind turbine blades are performed using a combination of FLUENT and FENSAP-ICE software,and the effects of liquid water content(LWC),medium volume diameter(MVD),wind speed and air temperature on blade icing shape are analyzed by two types of ice,namely rime ice and glaze ice.The results show that the increase of LWC and MVD will increase the amount of ice that forms on the blade surface for either glaze ice or rime ice,and an increase of MVD will expand the adhesion surface between ice and blade.Before reaching the rated wind speed of 11.4 m/s,it does not directly affect the icing shape.However,after reaching the rated wind speed,the attack angle of the incoming flow decreases obviously,and the amount of ice increases markedly.When the ambient air temperature meets the icing conditions of glaze ice(i.e.,−5℃ to 0℃),the lower the temperature,the more glaze ice freezes,whereas air temperature has no impact on the icing of rime ice.Compared with onshore wind turbines,offshore wind turbines might face extreme meteorological conditions,and the wind speed has no impact on the amount of ice that forms on the blade surface for most wind speeds.

关键词： environmental parameters cold regions offshore wind turbine rime glaze numerical simulation

Reliability-based design optimization of offshore wind turbine support structures using RBF surrogate model

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Frontiers of Structural and Civil Engineering 2023年第7期17卷 1086-1099页

作者： Changhai YU Xiaolong LV Dan HUANG Dongju JIANG Department of Engineering Mechanics Hohai UniversityNanjing 211100China

An efficient reliability-based design optimization method for the support structures of monopile offshore wind turbines is proposed herein.First,parametric finite element analysis(FEA)models of the support structure are established by considering stochastic variables.Subsequently,a surrogate model is constructed using a radial basis function(RBF)neural network to replace the time-consuming FEA.The uncertainties of loads,material properties,key sizes of structural components,and soil properties are considered.The uncertainty of soil properties is characterized by the variabilities of the unit weight,friction angle,and elastic modulus of soil.Structure reliability is determined via Monte Carlo simulation,and five limit states are considered,i.e.,structural stresses,tower top displacements,mudline rotation,buckling,and natural frequency.Based on the RBF surrogate model and particle swarm optimization algorithm,an optimal design is established to minimize the volume.Results show that the proposed method can yield an optimal design that satisfies the target reliability and that the constructed RBF surrogate model significantly improves the optimization efficiency.Furthermore,the uncertainty of soil parameters significantly affects the optimization results,and increasing the monopile diameter is a cost-effective approach to cope with the uncertainty of soil parameters.

关键词： reliability-based design optimization offshore wind turbine parametric finite element analysis RBF surrogate model uncertain soil parameter

Simulation of offshore wind turbine Blade Docking Based on the Stewart Platform

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Energy Engineering 2023年第11期120卷 2489-2502页

作者： Yi Zhang Jiamin Guo Huanghua Peng College of Ocean Science and Engineering Shanghai Maritime UniversityShanghai201306China

The windy environment is the main cause affecting the efficiency of offshore wind turbine installation.In order to improve the stability and efficiency of single-blade installation of offshore wind turbines under high wind speed conditions,the Stewart platform is used as an auxiliary tool to help dock the wind turbine blade in this paper.In order to verify the effectiveness of the Stewart platform for blade docking,a blade docking simulation system consisting of the Stewart platform,wind turbine blade,and wind load calculation module was built based on Simulink/SimscapeMultibody.At the same time,the PID algorithm is used to control the Stewart platform so that the blade can effectively track the desired trajectory during the docking process to ensure the successful docking of the blade.Through the simulation of the docking process for blades with a length of 61.5 meters,this paper successfully demonstrates a docking system that might facilitate future docking processes.It also shows that the Stewart platform can effectively reduce the vibration and the movement range of the blade root and improve the stability and efficiency of blade docking.

关键词： offshore wind turbine Stewart platform blade docking PID simscape multibody

海上风电吸力式三筒导管架基础在砂土中的调平技术试验研究

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Journal of Marine Science and Application 2022年第4期21卷 192-204页

作者：张浦阳马宇轩乐丛欢丁红岩 State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China School of Civil Engineering Tianjin UniversityTianjin 300072China

For the tripod bucket jacket foundations used in offshore wind turbines, the probable critical tilt angles should be avoidedduring tilt adjustment operation. Thus, these critical values must be identified by engineers, and remedial techniques mustbe established prior to the occurrence of the problem. Model tests were carried out for typical tilting conditions of tripodbucket foundations, which were allowed to tilt freely at various penetration depths without interruption by manualoperation. After the foundation ceased its tilting, some measures, such as water pumping, water injection, air injection, or acombination of the above methods, were enabled for adjustment. The research results showed two critical values in thetilting state of the tripod bucket jacket foundation, namely the terminal and allowable angles. In the installation condition,the terminal angle was negatively correlated with the initial penetration depth, but the opposite was observed with theremoval condition. The allowable angle was less than or equal to the terminal angle. The allowable angle in the installationwas related to the terminal angle. The critical angles all varied linearly with the initial penetration depth. When tiltingduring installation, adjustment measures can be used in the order of high drum pumping, low drum water injection, highdrum pumping and low drum water injection, air injection, and exhaust. When tilting during removal, the sequential use oflow drum water injection, air, and exhaust was applied. For buckets that were sensitive to angle changes, adjustmentmeasures of the “point injection” mode can be selected.

关键词： Tripod bucket jacket foundation Tilt adjustment Penetration and removal Terminal angle Allowable angle offshore wind turbine

A simplified method for analyzing the fundamental frequency of monopile supported offshore wind turbine system design

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Earthquake Engineering and Engineering Vibration 2018年第4期17卷 893-901页

作者： Yang Chunbao Wang Rui Zhang Jianmin School of Civil Engineering/State Key Laboratory of Hydroscience and Engineering Department of Hydraulic Engineering Tsinghua University

Preliminary design of offshore wind turbines requires high precision simplified methods for the analysis of the system fundamental frequency. Based on the Rayleigh method and Lagrange’s Equation, this study establishes a simple formula for the analysis of system fundamental frequency in the preliminary design of an offshore wind turbine with a monopile foundation. This method takes into consideration the variation of cross-section geometry of the wind turbine tower along its length, with the inertia moment and distributed mass both changing with diameter. Also the rotational flexibility of the monopile foundation is mainly considered. The rigid pile and elastic middle long pile are calculated separately. The method is validated against both FEM analysis cases and field measurements, showing good agreement. The method is then used in a parametric study, showing that the tower length Lt, tower base diameter d0, tower wall thickness δt, pile diameter db and pile length Lb are the major factors influencing the fundamental frequency of the offshore wind turbine system. In the design of offshore wind turbine systems, these five parameters should be adjusted comprehensively. The seabed soil condition also needs to be carefully considered for soft clay and loose sand.

关键词： offshore wind turbine system fundamental frequency analytical method rotational foundation flexibility

Shaking table test and numerical analysis of offshore wind turbine tower systems controlled by TLCD

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Earthquake Engineering and Engineering Vibration 2015年第1期14卷 55-75页

作者： Chen Jianbing Liu Youkun Bai Xueyuan State Key Laboratory of Disaster Reduction in Civil Engineering & School of Civil Engineering Tongji University Shanghai Electric Power Design Institute Co. Ltd Jiang Architects & Engineers

A wind turbine system equipped with a tuned liquid column damper （TLCD） is comprehensively studied via shaking table tests using a 1/13-scaled model. The effects of wind and wave actions are considered by inputting response- equivalent accelerations on the shaking table. The test results show that the control effect of the TLCD system is significant in reducing the responses under both wind-wave equivalent loads and ground motions, but obviously varies for different inputs, Further, a blade-hub-tower integrated numerical model for the wind turbine system is established. The model is capable of considering the rotational effect of blades by combining Kane＇s equation with the finite element method. The responses of the wind tower equipped with TLCD devices are numerically obtained and compared to the test results, showing that under both controlled and uncontrolled conditions with and without blades＇ rotation, the corresponding responses exhibit good agreement. This demonstrates that the proposed numerical model performs well in capturing the wind-wave coupled response of the offshore wind turbine systems under control. Both numerical and experimental results show that the TLCD system can significantly reduce the structural response and thus improve the safety and serviceability of the offshore wind turbine tower systems. Additional issues that require further study are discussed.

关键词： offshore wind turbine shaking table test TLCD numerical model vibration control

Gravity Effect on the First Natural Frequency of offshore wind turbine Structures

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Transactions of Nanjing University of Aeronautics and Astronautics 2016年第1期33卷 95-101页

作者： Ma Hongwang Chen Longzhu Department of Civil Engineering Shanghai Jiao Tong University

The fatigue limit state is critical for most offshore wind turbine.To minimize the development of fatigue damage,dynamic amplification of the response must be avoided.Thus,it is important to ensure that the first natural frequency of the offshore wind turbine does not coincide with the excitation frequencies related to wind turbine and wave loadings.For evaluating the self-gravity influence on the first natural frequency of wind turbine support structures,the offshore wind turbine system vibration is modeled using an Euler-Bernoulli beam with axial force and horizontal force.Real data from five wind turbines available in the market are considered.The sizes of wind turbines vary from 2.3MW to 6MW,and subsequently,the heights of tubular steel towers vary from 83 mto 100m.Results indicate that the average influence of gravity on the first natural frequency is nearly 1.8%.The first natural frequency is considered ranging from 1P(rototor frequency)to 3P(blade passing frequency).The design procedure requires an accurate evaluation of the first natural frequency.From this perspective,the first natural frequency is reduced since gravity needs to be considered for the design of offshore wind turbine support structures,especially when the first natural frequency of the offshore wind turbine is close to the lower limit,rotor frequency1 P.

关键词： offshore wind turbine the first natural frequency gravity Euler-Bernoulli beam

Movement pattern of red seabream Pagrus major and yellowtail Seriola quinqueradiata around offshore wind turbine and the neighboring habitats in the waters near Goto Islands, Japan

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Aquaculture and Fisheries 2021年第3期6卷 300-308页

作者： Khyria Swaleh Karama Yoshiki Matsushita Masahiro Inoue Kenta Kojima Kazuki Tone Itsumi Nakamura Ryo Kawabe Graduate School of Fisheries and Environmental Sciences Nagasaki UniversityNagasaki852-8521Japan Kenya Marine and Fisheries Research Institute P.O.Box81651-80100Mombasa20100Kenya Organization for Marine Science and Technology Nagasaki UniversityNagasaki852-8521Japan Nagasaki Branch Fisheries Infrastructure Development CenterNagasaki850-0035Japan Faculty of Fisheries Nagasaki UniversityNagasaki852-8521Japan Institute for East China Sea Research Organization for Marine Science and TechnologyNagasaki UniversityNagasaki851-2213Japan

We investigated movement pattern of commercial important fish around offshore wind turbine(OWT)and neighboring habitats in Goto Islands.We tagged 55 individuals of 2 fish species and released around the OWT in 2017.(27 Pagrus major from 1st Feb 2017 to 16th Mar 2017(winter),8 P.major and 20 Seriola quinqueradiata from 13th July 2017 to 13th Oct 2017(summer)).Acoustic receivers were deployed at OWT,south artificial reef(AS),trapnet(TN),north FAD(F1)and south FAD(F2)in winter and two more receivers were deployed at north artificial reef(AN)and natural reef(NR)in summer.We observed 12 P.major at OWT for a day after released in winter,majority of fish(13 individuals)were detected at TN.In summer,7 P.major were observed at OWT,1 visited TN within the day,but others disappeared.Ten S.quinqueradiata stayed at OWT longer than P.major after released and disappeared within 2 days.They mostly moved around AS,AN,NR.Residence time from K-M curve was 10 days for P.major in winter,a day in summer and 3 days for S.quinqueradiata.Both species showed low affinity for OWT as recorded low residency index despite the season.

关键词： Biotelemetry Habitat usage offshore wind turbine Red seabream Pagrus major Yellowtail Seriola quinqueradiata