Dynamic Response Analysis of A 5 MW NREL Wind Turbine Blade under Flap-Wise and Edge-Wise Vibrations

A wind turbine is subjected to a regime of varying loads.For example,each rotor revolution causes a complete gravity stress reversal in the low-speed shaft,and there are varying stresses from the out-of-plane loading cycle due to fluctuating wind load.Consequently,wind turbine blade design is governed by fatigue rather than ultimate load considerations.Previous studies have adopted many different beam theories,using different techniques and codes,to model the National Renewable Energy Laboratory(NREL)5MWoffshore wind turbine blade.There are differences,from study to study,in the free vibration results and the dynamic response.The contribution of this study is to apply the code written by the authors to the different beam theories used with the aim of comparing the different beam theories presented in the literature and that developed by the authors.This paper reports the investigation of the effects of deformation parameters on the dynamic characteristics of the NREL 5 MW offshore wind turbine blades predicted by the different beam theories.The investigation of free vibrations is a fundamental step in the analysis of structural dynamics,and this study compares different computational structural methods and investigates their effect on the predicted dynamic response.The modal characteristics of every model examined have been combined with strip theory to determine the dynamic response of the blade.

Vibration analysis of large bulb tubular pump house under pressure pulsations

A 3D finite element model of the Huaiyin third pumping station of the Eastern Route of the South-to-North Water Transfer is described in this paper. Two methods were used in the calculation and vibration analysis of the pumping station in both the time domain and the frequency domain. The pressure pulsation field of the whole flow passage was structured on the basis of pressure pulsations recorded at some locations of the physical model test. Dynamic time-history analysis of the pump house under pressure pulsations was carried out. At the same time, according to spectrum characteristics of the pressure pulsations at measuring points and results of free vibration characteristics analysis of the pump house, the spectrum analysis method of random vibration was used to calculate dynamic responses of the pump house. Results from both methods are consistent, which indicates that they are both reasonable. The results can be used for reference in anti-vibration safety evaluation of the Huaiyin third pumping station.

Wind Vibration Study of Long-span Steel Arch Structure of Beijing Capital International Airport

The wind-induced dynamic response of long-span light-weight steel arch structure of the global transportation center (GTC) of Beijing Capital International Airport was studied. A composite technique with combination of WAWS(Weighted Amplitude Wavelet Superposition) and FFT(Fast Fourier Transformation) was introduced to simulate wind velocity time series of hundreds of spatial points simultaneously. The structural shape factors of wind load was obtained from wind tunnel model test. The wind vibration factor based on structural displacement response was investigated. After comparing the computational results with wind tunnel model test data, it was found out that the two results accord with each other if wind comes from 0° direction angle, but are quite different if wind comes from 180° direction angle in the area blocked off by airport terminals. The possible reasons of this difference were analyzed. Haar wavelet was used to transform and analyze wind velocity time series and structural wind-induced dynamic responses. The relationship between exciting wind loads and structural responses was studied in time and frequency domains.

Evaluating effectiveness of multiple tuned mass dampers for vibration control of jacket offshore wind turbines under onshore and seafloor earthquakes

The dynamic characteristics and structural responses of operation and grid loss offshore wind turbines(OWTs)under onshore and seafloor earthquakes are analyzed based on the established coupled seismic analysis model.In addition to the remarkable influence of the rotor system on the responses of the operation OWT under earthquakes,interactions among the natural modes of the grid loss OWT in the fore-aft and side-to-side directions are revealed.By comparing with the onshore earthquakes,the more significant differences of structural response are observed under the selected seafloor earthquakes,due to the longer duration and more abundant energy distribution around the natural frequencies of OWT.Concurrently,a multiple tuned mass damper(MTMD)is designed and applied to the operation and grid loss OWTs.Then,the comparisons of the mitigation effects under onshore and seafloor ground motions are carried out,and the necessity of applying seafloor ground motions to OWTs are proved.Moreover,in comparison to the operation OWT,more effective reductions are observed for the grid loss OWT under onshore and seafloor earthquakes using the designed MTMD.Therefore,the combined shutdown procedures and MTMD vibration control strategy is suggested for OWTs under earthquakes.

A More Precise Computation of Along Wind Dynamic Response Analysis for Tall Buildings Built in Urban Areas

Modern tall buildings are generally built in urban areas, where value of the terrain roughness length is much greater than that of the general terrain areas, therefore wind-induced vibrations become more pronounced. The present formulas of numerical analysis of wind-induced response become less accurate. A more accurate expression of along-wind load spectrum matrix is proposed. On the basis of the expression, structural analysis formula of along-wind displacement and acceleration response are developed and programmed. The rationality of these formulas are illustrated in examples.

The Transient Modal Dynamic Analysis of a Coke Tower

Dynamic analysis must be performed when the duration of the applied load is short or if the load is dynamic in nature. Wind load, as a random load, can lead to the vibration of the coke tower. In order to study the influence to the strength of the coke tower by wind, ABAQUS was used to conduct the transient modal dynamic analysis of the wind load. The response of the structure during loading and unloading was mainly observed. The results indicate that, with the effect of wind, the maximal nodal displacement appears at the top of the tower, which is 0.79 mm; while the maximal stress locates at the node around the skirt, the maximum is 3.26 MPa. Both of the displacement and stress cannot cause the failure of the structure. After loading and unloading, the structure engenders vibration along the loading direction. The frequency is 10 Hz, under the effect of external loads, it may easily cause the resonance of the structure, which can cause damage to the structure. So it must be taken into consideration during the process of design and operation.

Software Practicalization for Analysis of Wind-Induced Vibrations of Large Span Roof Structures

Wind loads are key considerations in the structural design of large-span structures since wind loads can be more important than earthquake loads, especially for large flexible structures. The analysis of wind loads on large span roof structures (LSRS) requires large amounts of calculations. Due to the com- bined effects of horizontal and vertical winds, the wind-induced vibrations of LSRS are analyzed in this pa- per with the frequency domain method as the first application of method for the analysis of the wind re- sponse of LSRS. A program is developed to analyze the wind-induced vibrations due to a combination of wind vibration modes. The program, which predicts the wind vibration coefficient and the wind pressure act- ing on the LSRS, interfaces with other finite element software to facilitate analysis of wind loads in the de- sign of LSRS. The effectiveness and accuracy of the frequency domain method have been verified by nu- merical analyses of practical projects.

水滴形大跨钢屋盖结构风洞试验和风振分析

自然风经过大跨结构时,由于结构屋顶形状不规则,通常会引起柔性屋面的振动,因此针对大跨屋面结构抗风设计需要考虑风压分布和风振响应。以陕西省水务集团矿泉水生产车间为工程背景,制作了1∶200的刚性模型,通过刚性模型风洞试验测得该水滴型大跨钢屋盖结构的表面风压,研究了屋盖表面典型测点及整体的风压分布规律。基于风洞试验数据,对结构进行风振时程分析,得到了屋盖表面的风振响应和风振系数。结合刚性模型风洞试验和风振分析,深入研究了水滴形大跨屋盖结构的风压分布规律和风致振动特性,并总结了其共性规律。

基于多特征提取和麻雀搜索算法优化XGBoost的变压器绕组松动诊断方法

针对使用单一特征量诊断变压器绕组松动,在不同负载条件下存在交叠和抗干扰能力不足的问题,提出一种基于核主成分分析(KPCA)和改进麻雀搜索算法(SSA)优化极端梯度提升(XGBoost)的变压器绕组松动振动诊断方法。首先,从时域、频域和熵值3个维度提取适用于变压器多传感器振动信号的多种特征量;其次,通过网格搜索优化的KPCA对特征量进行降维;最后,构建基于XGBoost的故障诊断模型,并采用改进麻雀搜索算法调参,实现不同电流大小下变压器绕组松动故障准确识别。以某110 kV变压器为对象进行实验验证,诊断结果表明,所提取的特征量能够准确反映故障特征,抗干扰能力更强,诊断模型故障诊断准确率为99.00%,相比于其他诊断算法准确率和稳定性更高,在不同负载情况下均有良好的识别效果。

双向恢复力模型对基础隔震建筑风振响应的影响

为明确MSS、Casciati和Harvey and Gavin这3种常用双向恢复力模型计算基础隔震建筑风振响应的差异,采用3种模型模拟铅芯橡胶支座在水平单向和双向位移下的恢复力,对比试验或有限元结果的差异,采用3种模型对一算例在双向风荷载下隔震层位移、顶点位移和顶点加速度3个指标的差异进行了分析。研究表明:3种模型模拟铅芯橡胶支座在单向循环位移、方形和偏置方形位移下恢复力的趋势基本一致;而模拟圆形和偏置圆形位移时,MSS模型双向恢复力形状与有限元结果不同,不能较为准确地模拟支座双向耦合行为,Casciati模型误差稍小于Harvey and Gavin模型。Casciati模型和Harvey and Gavin模型计算风振响应基本一致;对于横风向响应均方根,3种模型差距不大;对于顺风向隔震层位移、顶点位移和顶点加速度均方根,MSS模型稍小,而对于顺、横风向隔震层位移峰值因子,MSS模型稍大;对于顺、横风向顶点加速度峰值因子和双向与单向模型顶点加速度最值比值随风速变化规律,MSS模型与其他模型差异较大。基于双向耦合效应模拟及风振响应指标的差异,建议采用Casciati模型考虑双向恢复力模型对基础隔震建筑风振响应的影响。

海上移动平台直升机甲板圆管支撑结构安全评估

圆管支撑结构是海上移动式平台直升机甲板设计的重要部分,由于海上恶劣的风浪环境,使结构整体受风载荷的影响较大.现有直升机甲板圆管支撑结构的安全评估内容主要集中于圆管的静强度分析,缺乏风振响应分析,文中以海洋石油163平台直升机甲板为例,研究圆管支撑结构的静力和动力载荷输入,通过有限元强度分析和理论经验公式计算对比静力、风载荷作用下直升机甲板圆管支撑结构的受力情况,考虑风振涡激效应的准静态分析,在此基础上提出了直升机甲板圆管支撑结构的安全评估方法,探究了风载荷对结构整体安全的影响.

形状记忆合金自复位减振装置研制与验证

为改善第二喉道中的可调中心体机构(简称中心体)在工作状态下的流致振动,根据形状记忆合金(shape memory alloy,SMA)偏置双程驱动原理,设计制作一种能够满足中心体有限安装空间要求的SMA自复位减振装置;采用UMAT接口编制的SMA本构关系子程序实现减振装置最大压紧力的数值分析,数值分析与静态调试试验结果误差约为2.58%;搭建地面减振试验平台,测试SMA自复位减振装置分离和闭合状态下的中心体零部件振动响应。减振试验结果显示:SMA自复位减振装置闭合后,中心体振动响应明显降低,在0~100 Hz频带内,均有明显的减振效果,低频至55 Hz范围内,减振率均大于50%。

台风风速下风力机风轮流固耦合动力响应特性研究

将改进的流固耦合方法用于不同风速下风力机的载荷和响应特性研究,其准确性得到NREL数据和风力机叶片模态振动实验的验证。与传统的流固耦合方法相比,该方法减少了动网格使用数量、避免负体积网格,提高了计算稳定性,将计算时间缩短约50%。仿真结果表明,将风速由25 m/s提升至35 m/s,叶片的推力和扭矩载荷的波动振幅分别增加了6.8倍和9.8倍。同时,在叶片吸力面发现存在结构屈曲,这与台风现场叶片断裂位置接近,可能是风力机叶片结构在台风环境下的强度薄弱点,同时,在叶片吸力面发现存在结构屈曲,这与台风现场叶片断裂位置接近,是可能的风力机叶片结构在台风环境下的强度薄弱点。

电力变压器绕组变形状态下的振动信号特性分析

近些年来国内电力变压器绕组机械故障频发,利用振动法监测电力变压器机械运行状态可以有效规避变压器故障风险。本文首先基于电力变压器绕组振动来源和加速度理论求解分析,搭建了110 kV电力变压器有限元模型,研究了变压器绕组在额定正常负载工况下的振动规律,发现了变压器在负载工况下绕组辐向振动强度远大于轴向振动,且绕组振动信号主频为100 Hz;在绕组上下端部固定约束条件下,其上下端振动强度小于绕组中间部位。然后,改变高压绕组几何形状使其发生鼓包变形,通过对比分析绕组未变形状态下的振动信号得出:当绕组发生形变时,其振动信号频谱中出现大量高次倍频谐波分量;随着绕组形变程度的加深,其振动信号主频不断增大,高次谐波分量分布也更为复杂。最后,通过定义基频占比、高频占比这两个特征参量,进一步分析了变压器绕组形变前后的振动特征变化规律,为实际现场利用振动法评估变压器绕组机械状态提供了依据。

调谐液柱阻尼器-结构系统风致振动响应的CFD/CSD耦合分析方法

针对调谐液柱阻尼器(tuned liquid column damper, TLCD)难以建立其精确的非线性理论分析模型,且其力学性能试验成本高和耗时长等问题,首先采用计算流体动力学(CFD)数值模拟方法,对TLCD系统的力学性能和动力特征进行仿真模拟,在此基础上进一步提出了基于计算流体动力学/计算结构动力学(CFD/CSD)耦合分析方法,求解带TLCD系统的高层建筑结构的风致动力响应。通过开展某一TLCD系统在特定底部激励下的力学性能和动力特性试验,得到其内液体晃荡的自由液面波高和晃动力时程,验证了CFD数值模拟方法可以准确地分析TLCD水箱内液体的非线性晃动特征。随后对风工程领域广泛采用的76层建筑结构振动控制Benchmark模型,假设其顶部设置TLCD系统时主体结构在三种风速重现期(10、50和100年)风速对应的横风向动力风荷载激励下的风致控制效率,采用提出的CFD/CSD耦合分析方法,进行了数值仿真模拟分析。耦合分析结果表明,TLCD系统对Benchmark模型的风致加速度、速度和位移响应均有一定的控制效果,对加速度响应的控制效果要优于对位移响应的控制效果。该研究方法可为复杂TLCD系统对高层建筑的风振控制分析提供有效的参考。

悬臂施工阶段大跨度拱桥抖振响应及抑振措施

为了探讨大跨度拱桥悬臂施工阶段的抖振位移响应及相应的抑振措施,以主跨400 m的中承式钢桁架拱桥为研究对象,首先建立了最大悬臂施工阶段拱桥结构的有限元模型,并基于谐波合成法模拟了三维空间脉动风场,然后采用时域分析方法计算了拱肋悬臂端和施工扣塔顶部的抖振位移响应,并利用风洞试验结果进行了对比验证,最后考察了不同抑振措施的减振效果。结果表明:在拱肋悬臂端设置竖向抗风缆能有效减小拱肋的竖向抖振位移响应;同时,设置倾角45°的扣塔抗风缆和拱肋抗风缆,可以使拱肋横桥向、竖向及扣塔横桥向、顺桥向抖振位移响应的减振率分别达到62.5%、84.8%、61.0%和62.7%。此外,采用空间交错方式和竖平面内交错方式“软连接”拱肋悬臂端,可以使拱肋横桥向、竖向及扣塔顺桥向抖振位移响应的减振率分别达到49.5%、95.7%和67.1%。以上结果证明大跨度拱桥悬臂施工期抖振减振效果与抗风措施的布设位置和方式密切相关,应合理选择适合的抗风措施。

Controlling structural vibrations in wind turbines by constructing function V

For a variable speed large scale wind turbine, the vibration issues become a key problem that cannot be ignored in the turbine＇s life cycle. Wind turbine tower vibration will cause superfluous mechanical loads. To resolve the vibration issue, a method for constructng the energy function V is proposed to meet the demands of safe operation. The Lyapunov theorem has been em- bedded in a wind turbine control algorithm, proving the theoretical feasibility of stability control based on function V. Accord- ing to an analysis of this complex nonlinear model for the wind turbine, the general method of constructing an energy function suitable for a wind turbine is presented explicitly. The feasibility of applying an energy function to wind turbine vibration con- trol is verified experimentally using a 3.0-MW direct drive wind turbine model. The experimental results indicate that the dy- namic performance of the tested wind turbine model with energy function control is significantly better than that of the uncon- trolled structure in terms of the reduction of nacelle acceleration, velocity, and displacement response.

Physics-based data analysis for wind turbine condition monitoring

This article presents methodologies for improving wind turbine condition monitoring using physics-based data analysis techniques.The unique operating conditions of the wind turbine drivetrain are described,and the complex kinematics of the gearbox is analyzed in detail.The pros and cons of the current wind turbine condition monitoring system(CMS)are evaluated.To improve the wind turbine CMS capability,it is suggested to use linear models with unsteady excitations,instead of using nonlinear and nonstationary process models,when dealing the wind turbine dynamics response model.An analysis is undertaken of the damage excitation mechanisms cause for various components in a gearbox,especially for those associated with lower-speed shafts.Physics(mechanics)-based data analysis methods are presented for different component damage excitation mechanisms.Validation results,using the wind farm and manufacturing floor data,are reported.

海岛输电塔线体系风振响应及易损性分析

以温州洞头海岛3572线新建的单回路猫头塔ZMG32-28.5及其所在塔线体系为研究对象,对输电塔的抗风性能评估展开研究。首先,采用ANSYS软件建立输电塔及其所在塔线体系的有限元模型,开展单塔和塔线体系的动力特性理论分析。随后根据台风风谱,采用谐波叠加法,生成具有台风特性的脉动风速时程。对塔线体系进行风振响应分析,了解塔线体系在设计风速作用下的塔身响应。最后考虑输电塔结构参数和脉动风荷载的不确定性,通过拉丁超立方抽样方法生成了80组塔线体系随机样本;通过谐波叠加法模拟生成80组具有台风特性的脉动风速时程。将塔线体系随机样本与风荷载一一对应组合,进行80组塔线体系的风振响应分析。对风振响应结果进行回归分析,得到考虑塔线耦合效应的输电塔风荷载作用效应函数和塔顶位移响应的均值和标准差值;此外,对生成的80组输电塔随机样本开展了静力弹塑性分析,确定输电塔结构的各极限状态限值和标准差值。基于上述两种分析计算结果,进行了考虑塔线耦合效应的输电塔风灾易损性分析,得到0°(顺线路)、90°(横线路)风向角工况下轻微破坏、中等破坏和倒塌破坏的风灾易损性曲线。研究表明,55m/s极值风速作用下,横线路风向较顺线路风向发生破坏概率增加8.25%,在遭受重现期100年风速(41.95m/s)时,横线路方向发生倒塌破坏概率为20.19%,ZMG32-28.5塔还是有较大的倒塌风险。

含减振子结构的模块化钢结构栈桥减振控制分析

为分析模块化钢结构栈桥水平方向减振控制,提出一种新型的结构体系—含减振子结构的模块栈桥结构。通过设计,用半刚性节点将带式输送机与栈桥主体结构相连接,在带式输送机底部与栈桥主体结构之间设置黏滞阻尼器,将带式输送机转变为减振子结构,形成含减振子结构的模块栈桥结构。采用有限元分析方法,在频域内以控制栈桥主体结构和带式输送机水平方向振动响应为目标,对半刚性节点刚度、阻尼系数进行参数分析,计算结果表明存在最优参数,可使模块栈桥水平方向振动得到控制。在时域内将含减振子结构栈桥设定为最优参数,分析其在风荷载作用下的减振效果。结果表明:这种体系能够较好地控制结构风振响应;存在最优的半刚性节点刚度系数和阻尼器阻尼系数,可以明显减小栈桥主体结构和带式输送机的风振动力响应。