Design of Offshore Wind Power Foundation with Multi-bucket

Three- and four-bucket offshore wind power foundations with a new form of force-transferring structure are proposed in this paper, and the integrated finite element model of foundation-soil-transition structure is established by using ABAQUS. The carrying capacity of the proposed foundations is studied under vertical load, horizontal load and bending moment. It can be seen that the vertical bearing capacity of multi-bucket foundation can be roughly estimated by the vertical bearing capacity of single-bucket; the horizontal bearing capacity of the three-bucket foundation scheme is controlled by displacement, while that of the four-bucket foundation scheme is controlled by the internal forces of soils. Moreover, the carrying capacity is provided by the overall structure formed by multi-bucket before soil failure. Compared with the conventional single-bucket foundation, there are mainly tension and pressure that are applied to the multi-bucket foundation, so that the carrying capacity of the foundation can be fully utilized. The probability of soil failure can be well reduced with the proposed multi-bucket foundation, and the stress transmission of force-transferring structure is more consistent through steel beams with variable cross-section.

Design of Large-Scale Prestressing Bucket Foundation for Offshore Wind Turbines

The key in the force transmission between the tower and the foundation for offshore wind turbines is to transfer the large moment and horizontal loads. The finite element model of a large-scale prestressing bucket founda- tion for offshore wind turbines is set up and the structural characteristics of the arc transition structure of the founda- tion are analyzed for 40-60 channels(20-30 rows) arranged with prestressing steel strand under the same ultimate load and boundary conditions. The mechanical characteristics of the key parts of the foundation structures are illus- trated by the peak of the principal tensile stress, the peak of the principal compressive stress and the distribution areas where the principal tensile stress is larger than 2.00 MPa. It can be concluded that the maximum principal tensile stress of the arc transition decreases with the increasing number of channels, and the amplitude does not change signifi- cantly; the maximum principal compressive stress increases with the increasing number of channels and the amplitude changes significantly; however, for the distribution areas where the principal tensile stress is larger than 2.00 MPa, with different channel numbers, the phenomenon is not obvious. Furthermore, the principal tensile stress at the top of the foundation beams fluctuantly increases with the increasing number of channels and for the top cover of the bucket, the principal tensile stress decreases with the increasing number of channels.

Research on the Critical Buckling Pressure of Bucket Foundations with Inner Compartments for Offshore Wind Turbines

In the process of suction penetration of bucket foundations with inner compartments for offshore wind turbines,most researches focus on soil seepage failure and soil plugs,while the buckling of foundations is rarely investigated.Therefore,theoretical calculation methods for critical buckling pressures of the skirt and bulkheads of the bucket foundation are first presented according to the stability theory of a cylindrical shell and the small deflection theory of a thin plate,respectively.Furthermore,two types of models with and without considering the skirt-soil interaction are developed for the calculation of critical buckling pressure of the bucket foundation.Taking a practical project as an example,theoretical and numerical methods are used to obtain the critical buckling pressures of a bucket foundation.In this work,the theoretical method and the finite element model considering the skirt-soil interaction for calculating the critical buckling pressure of bucket foundations are firstly proposed.The results can help to optimize the design process of offshore wind turbine foundations and improve the safety of offshore wind power systems.

European Offshore Wind Gravity Foundation

The development history of the offshore wind gravity foundation in Europe is briefly introduced.Sumnarized in which the equipment relates to offshore wind power installation,including ships and special equipment related to wind power installation.And the installation method and technology of gravity foundation are analyzed.The development trend of the offshore wind power gravity foundation is put forward.

Numerical Analysis of a Gravity Substructure for 5 MW Offshore Wind Turbines Due to Soil Conditions

In order to increase the gross generation of wind turbines, the size of a tower and a rotor-nacelle becomes larger. In other words, the substructure for offshore wind turbines is strongly influenced by the effect of wave forces as the size of substructure increases. In addition, since a large offshore wind turbine has a heavy dead load, the reaction forces on the substructure become severe, thus very firm foundations should be required. Therefore, the dynamic soil-structure interaction has to be fully considered and the wave forces acting on substructure accurately calculated. In the present study, ANSYS AQWA is used to evaluate the wave forces. Moreover, the substructure method is applied to evaluate the effect of soil-structure interaction. Using the wave forces and the stiffness and damping matrices obtained from this study, the structural analysis of the gravity substructure is carried out through ANSYS mechanical. The structural behaviors of the strength and deformation are evaluated to investigate an ultimate structural safety and serviceability of gravity substructure for various soil conditions. Also, the modal analysis is carried out to investigate the resonance between the wind turbine and the gravity substructure.

Coupled Time-Domain Investigation on a Vertical Axis Wind Turbine Supported on a Floating Platform

The dynamic responses of a floating vertical axis wind turbine(VAWT)are assessed on the basis of an aero-hydro-mooring coupled model.The aerodynamic loads on the rotor are acquired with double-multiple stream tube method.First-and second-order wave loads are calculated on the basis of 3D potential theory.The mooring loads are simulated by catenary theory.The coupled model is established,and a numerical code is programmed to investigate the dynamic response of the semi-submersible VAWT.A model test is then conducted,and the numerical code is validated considering the hydrodynamic performance of the floating buoy.The responses of the floating VAWT are studied through the numerical simulation under the sea states of wind and regular/irregular waves.The effects of the second-order wave force on the motions are also investigated.Results show that the slow-drift responses in surge and pitch motions are significantly excited by the second-order wave forces.Furthermore,the effect of foundation motion on aerodynamic loads is examined.The normal and tangential forces of the blades demonstrate a slight increase due to the coupling effect between the buoy motion and the aerodynamic loads.

Stability Study on the Bucket Foundation with Multi-Compartment During the Floating-up Process Considering Air Compressibility

In the process of developing offshore wind power towards deeper waters,the advantages of the bucket foundation in terms of integrated construction and economy are becoming increasingly evident.In contrast to conventional floating bodies,the air-floating bucket foundations can achieve self-floating with the help of the air in the compartment and adjust its buoyancy and stability by controlling the air volume in the compartment.The construction process of the bucket foundation involves the control of air in the compartment,thus making it more difficult to construct.Especially after the prefabrication of the bucket foundation,the stability of the bucket foundation at the floating-up stage is particularly critical.The stability of a multi-compartment bucket foundation during the floating-up process cannot be accurately evaluated as the existing theoretical method of air-floating structures does not adequately consider air compressibility.To ensure the safety of the floating-up process,a theoretical method based on the idea of intact stability has been developed to analyze the stability of the air-floating bucket foundations,which will allow accurate calculation of the righting arm for different tilt states and critical air leakage angle.At the same time,accuracy and feasibility of the proposed theoretical method are verified through indoor model tests and practical operation of the prototype structure during the floating-up process.In addition,measures to enhance the stability of the bucket foundation are proposed through sensitivity analysis of influencing factors.

考虑气动阻尼影响的海上风电筒型基础整机运行状态振动模拟研究

运行状态下由叶轮旋转效应产生的气动阻尼对海上风电结构振动影响显著,然而当前的数值模拟方法受到计算能力与施加气动阻尼方式的限制,无法真实高效地表征气动力对振动的影响,使得模拟结果与实际工程存在偏差。针对上述问题,以某海上风电场内1台筒型基础整机为研究对象,考虑气动阻尼效应搭建了整机顺风向振动的简化理论模型,研究气动阻尼对运行状态下整机振动的折减效果,并以折减系数形式引入到数值模型计算中再与原型观测结果进行对比。研究表明:所建理论模型与数值模型的一阶自振频率与实测数据反馈值均相差较小,两类模型对实际工程的适用性良好;理论模型与数值模型同风速下的振动差值稳定,两者动力学上具有很好的同步性;停机工况与运行工况下,模拟塔筒顶部振动位移均方根值与原型观测均方根值平均误差分别为12.19%与7.99%,说明基于考虑气动阻尼效应的振动理论模型对数值模拟结果进行折减是可行的,模拟精度可以满足工程需求。

海上桩基础注水加压拆除法的研究

近年来,全球海上风电发展势头迅猛.单桩基础作为最早应用于海上风电的基础类型,在全球风场中占据主导地位.现有风机的寿命一般约为20年,预计未来10年将迎来大量风机退役,这使得海上桩基础的回收问题变得愈发重要.为更好地解决海上桩基础退役拆除问题,本文通过物理模型实验的方式对注水加压拆除法进行了研究.实验结果显示:大直径桩基础拆除时所需压强更小,更易通过注水加压拆除法进行拆除;桩基础初始倾角对注水加压拆除所需压强影响较小,但初始倾角越大基础越易倾倒;拆除过程中桩基础单位位移引起的舱内压强下降幅度始终相同,不受基础直径、入泥深度以及倾角的影响.根据物理模型实验数据,结合土力学、水力学相关理论,建立了注水加压拆除法全过程理论模型,可大致预测不同桩径、不同入泥深度桩基础的启动舱内压强与舱内压强-位移曲线,并且在此基础上,结合渗流计算,利用有限元模型对水泵在注水回收过程中可产生的最大舱内压强进行了预测,对比最大舱内压强与基础拆除所需的启动舱内压强即可判断此水泵能否用于注水加压拆除.本文所得结论可为海上风电桩基础的退役处理提供参考,有助于保障风场海床资源的可持续利用,具有一定的工程价值.

砂土中桩靴插桩对临近筒型基础的影响研究

通过物理模型试验和有限元法研究砂土中风电安装船桩靴插桩对临近筒型基础的影响。首先通过物理模型试验,验证有限元模型的合理性,初步确定桩靴在砂土中贯入的影响范围大致在2.5倍桩靴直径。基于有限元CEL方法进一步研究桩靴和筒型基础的净距与桩靴直径之比(S/D)对筒型基础在位稳定性的影响。结果表明:筒型基础的倾斜率、最大竖向位移以及筒壁应力随着S/D的增大而逐渐减小,插桩过程中,靠近桩靴一侧的筒裙和分舱板应力远大于远离桩靴一侧的筒型基础应力,且筒顶的土压力远小于筒底土压力。

海上风电五连筒导管架基础及筒顶节点受力分析

以广东某深远海域大容量风电机组五连筒导管架基础为研究对象,采用有限元软件对五连筒基础在倾斜率、极限承载力和屈曲特性等方面开展深入研究,并对筒顶处导管架与基础连接节点进行多参数敏感性分析,从而得到受力及承载最优的结构体型。研究结果表明:满足相同容量机组荷载运行要求的前提下,五连筒基础与单筒基础结构相比,前者在倾斜率、承载力及抗屈曲特性上优势明显;随着筒顶节点的外移,筒型基础边筒竖向变形逐渐增大,中筒则相反;当筒顶节点靠近中筒时,主要由中筒受力,应力最大部位主要集中在边筒和中筒筒裙底部连接处;当筒顶节点向外偏移时,受力部位由中筒转移到边筒,且应力最大部位转移到沿加载方向的边筒筒裙顶部;基础的极限承载力均随导管架根部开度增加呈线性趋势增长,在水平及弯矩荷载分别作用下,旋转中心附近的被动土压力受筒顶节点位置影响较大,筒顶节点越往外偏移,被动土压力越小;旋转中心以下的主动土压力受筒顶节点位置影响同样较大,筒顶节点越往外偏移,主动土压力越大。

海上风电三筒导管架基础的湿拖耦合动力响应研究

[目的]为提高海上风电多筒导管架基础的湿拖运输安全性,需探究其湿拖运输过程的稳性和动态响应问题。[方法]基于海工分析软件MOSES构建水动力模型,对湿拖运输过程分别进行频域和时域分析,并定量分析波浪载荷、拖航方式等参数对三筒导管架基础拖航特性的影响。[结果]计算结果表明,三筒导管架具有良好的湿拖稳性,在吃水深度8~10 m范围内的正浮态均可满足完整稳性校核;三筒导管架基础的拖缆力、纵摇角、垂荡加速度、筒气压的幅值与波高呈正比关系,与吃水深度呈线性变化关系但影响较小;拖缆力和筒气压的幅值与波浪周期无明显关系,但波浪周期将影响该基础的纵摇和垂荡响应幅值;拖缆力与航速的平方近似呈正比关系;顺浪条件下三筒导管架基础的纵摇运动比逆浪条件更为剧烈。[结论]研究成果对于提高多筒导管架基础的湿拖运输安全性具有重要的指导意义。

基于HSS模型海上风电桶形基础水平循环承载特性对比研究

采用土体本构模型对黏土中的桶形基础进行了有限元模拟,以研究桶形基础的水平循环承载特性。利用有限元方法模拟了在不同单调组合荷载作用下黏土中的桶形基础离心机试验,与试验结果对比验证了使用小应变硬化土(HSS)本构模型的适用性。在此基础上,基于HSS模型和硬化土(HS)模型对比研究了不同循环荷载和小应变模量对桶形基础累积转角、旋转中心和桶-土相对刚度的影响。结果表明,黏土中桶形基础的累积转角随着循环次数和水平荷载的增加而增加,然而每个循环中累积转角的增加逐渐减小。另外,提出了Tb和ζb之间的拟合关系式预测黏土中桶形基础的累积旋转。无论处于疲劳极限状态(ζb=0.3)还是正常使用极限状态(ζb=0.5),旋转中心类型都是从深中心变为浅中心。桶-土相对刚度随循环次数的增加而减小,并且循环荷载越大刚度衰减越大。另外,小应变模量对基础累积转角和桶-土相对刚度有较大影响而对旋转中心无显著影响。与已有的研究结果对比发现,HSS模型更加适用于精细化设计。

海上风机与养殖网箱融合系统中网箱系泊绳张力与导管架基础结构的安全性

海洋牧场与海上风电融合发展是现代渔业和清洁能源产业融合发展的典型代表,有利于构建“海上粮仓+清洁能源”的新产业模式。本研究基于福建漳浦六鳌海上风电场风机导管架构建养殖网箱与海上风机融合系统,运用Aqua-FE™有限元工具探究极端波流条件下不同网箱布设深度、波流入射角、生物附着程度对网箱系泊绳张力的影响;采用海洋工程专用设计软件SACS,计算分析风机导管架结构在波流及网箱系泊绳张力作用下的应力分布,评估养殖网箱系泊绳张力对风机导管架基础结构安全性的影响。结果显示,网箱布设深度的增加能够减少网箱系泊绳最大张力,显著改善网箱风机整体结构受力状态;波流入射角的改变对于网箱风机整体结构安全性影响不大;网衣生物附着程度的增加会显著增加网箱系泊绳最大张力,从而造成风机导管架基础杆件大量失效。研究表明,养殖网箱可布设于适当水深以减少受力,同时应及时清理附着生物,适当增加网箱系泊点附近的导管架杆件和导管架底部桩土点杆件的壁厚,以确保养殖网箱与海上风机融合系统结构安全。该结果可为深入研究网箱与风机融合系统的受力,评估该系统的安全性,优化设计养殖网箱与风机融合系统提供数据支撑。

复合加载下海上风电四筒基础地基承载力特性研究

以福建某海上风电场四筒导管架基础为研究对象,通过数值模拟方法建立四筒基础-地基整体模型,研究四筒基础在V-H(竖向-水平荷载)、V-M(竖向-弯矩荷载)、H-M(水平-弯矩荷载)和V-H-M(竖向-水平-弯矩荷载)作用下的地基失效模式。结果表明:在V-H和H-M加载模式下,四筒基础竖向极限承载力和弯矩极限承载力均随着水平力的增大而减小,且弯矩极限承载力与水平力之间呈现出线性减小的趋势;在V-M加载模式下,随着竖向荷载的不断增大,四筒基础主要运动形式从转动转换为平动;V-H-M加载模式下的承载力包络线随着竖向荷载的增大向外扩张,且竖向荷载的作用明显提高了地基水平和弯矩极限承载力。

基于声波逆时偏移成像的海上风电基础冲刷坑监测方法

海上风电基础冲刷是目前海上风电基础面临的普遍问题,冲刷坑的探测与监测对保障桩基安全十分重要。针对现有探测方法存在成本高、无法准确描述冲刷坑发展和形态等缺陷,提出一种基于声波逆时偏移的监测方法,首先采用有限差分方法求解声波方程模拟在海上风电桩基上布置震源的声波传播过程,分析冲刷坑界面反射波的波场特征;在此基础上,提出一种线性观测系统用于监测冲刷坑发展过程,并提出基于逆时偏移的冲刷坑表面成像方法,通过多组数值模拟试验验证该方法对不同规模和形态的冲刷坑都有良好的成像效果,最大冲刷深度误差均在10%以内。最后采用沙坑模型试验进一步证明提出冲刷坑监测方法的有效性。

我国海上风电发展现状与趋势综述

近年来,在碳达峰目标与碳中和愿景下,海上风电在我国取得了长足的发展。分析了我国目前海上风电的发展现状与未来规划,对海上风电装机规模、新增机型以及采用的技术路线进行了汇总。重点介绍了海上风电基础型式、防腐技术和运维技术,其中,漂浮式海上风电是基础型式研究的重点,运维巡检和运维管理系统是风电运维技术研究的重点。通过分析海上风电的发展状况,整理了各项技术的主要技术路线和先进成果。最后,基于目前国内的技术发展现状及需求,对我国海上风电未来发展趋势进行展望。

砂土中筒型基础临界吸力计算方法研究

开展砂土中筒型基础吸力沉贯的系列模型试验,测试筒型基础下沉过程中吸力的发挥过程,并通过反分析得出筒内外土体渗透系数比的变化规律。结果表明:当筒内土体出现管涌现象时,筒内负压会瞬间降低;随着沉贯深度的增加,临界吸力值也逐渐增大;此外,筒内外土体的渗透系数比呈指数函数型增长;假设在沉贯过程中土体的渗透系数不变,则临界吸力的预测结果均小于实测值。根据试验结果改进砂土中筒型基础沉贯过程临界吸力的计算公式,并进行工程案例验证。

海上漂浮式风电机组塔筒优化方法研究

为适应复杂多变的海上环境,高效利用风资源、减少用钢成本,开展漂浮式风电机组塔筒的结构优化设计。以船载风电机组为研究对象,引入漂浮式基础的动态响应,作为影响塔筒弯曲变形的重要约束条件。在保证风电机组稳定功率输出的前提下,以质量最轻为优化目标,以塔筒构造要求和规范为基本约束条件,建立漂浮式基础风电机组塔筒的数值优化模型,并利用遗传算法完成了模型优化。结果显示,在保证风电机组稳定性和正常功率输出要求下,塔筒的质量降低了35%,刚度提高了25%。

四浮筒半潜式海上风机基础水动力性能分析

参照三浮筒式OC4半潜式风机基础,设计了四浮筒式浮式风机基础。建立三浮筒式OC4半潜式风机基础与四浮筒式浮式风机基础水动力模型,利用AQWA软件分析四浮筒式浮式风机基础相关水动力参数,并将四浮筒式浮式风机基础与三浮筒式OC4半潜式风机基础进行不同工况下的时域分析对比,探究两者间性能差异。结果表明,四浮筒式浮式风机基础具有良好的水动力性能,相较于三浮筒式OC4半潜式风机基础,其在纵荡、横荡、纵摇、艏摇4个自由度方向上的运动响应以及缆绳张力方面存在优势。