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本文对线性和非线性气动力的叶片气动弹性响应进行了讨论。由连续气弹方程采用伽辽金法离散,导出了一些有关矩阵。采用wilson-θ法计算响应。最后给出了两个算例。 相似文献
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大型化趋势下风力机叶片刚度降低,出现颤振的风险增加,且风力机在运行中不可避免受到非均匀来流的影响。为考虑这一问题,对垂直方向波动来流中具有结构非线性的翼型气弹稳定性进行研究。基于小攻角假设,采用线性气动力模型建立考虑三次硬化刚度与非均匀来流作用下的二自由度二维翼型气弹模型,并通过数值积分方法对翼型气弹系统的动力学方程进行求解,得到不同来流工况下翼型系统的稳态响应形式。从时域、相轨迹以及频域上对获得的翼型振动信号特征进行分析,结果表明翼型受到垂直方向来流的激振作用出现强迫振动,在低流速下和临界速度附近造成振动强度明显放大,模糊颤振边界并使诱发颤振条件下翼型振动更加剧烈;在波动来流作用下气弹失稳的俯仰振动能量在一个频率带上分布,且在高于颤振频率的位置存在另一峰值,标志颤振的诱发是由俯仰振动受到气动力影响耦合到沉浮频率上所导致。 相似文献
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为了探究大型风力机柔性叶片在挥舞-摆振耦合作用下的气弹稳定性,文章基于ONERA非线性气动模型建立了包括二维翼型非线性气动升阻力方程及其挥舞-摆振耦合运动方程的气弹模型。利用该气弹模型计算得到NREL 5 MW风力机叶中段DU35-A17翼型在叶片变桨前后的挥舞、摆振变形量变化曲线,并与FAST计算结果进行比较,以验证气弹模型的准确性。结果表明:在额定工况时,叶片出现z轴正方向、y轴负方向的弯曲变形;风力机未变桨时,挥舞、摆振变形量会随风速增大而增大;叶片变桨后,挥舞、摆振变形量会比额定工况下的变形量有所减少。由于计算得到的挥舞、摆振变形量曲线是收敛的,故叶片是气弹稳定的。该气弹模型为评估大型风力机柔性叶片气弹稳定性提供了新方法,计算得到的挥舞摆振位移数据为优化风力机结构参数、提升叶片气弹稳定性提供了数据参考。 相似文献
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摘要: 建立了一种用于计算海上浮式风机运动响应的时域耦合方法,该算法主要由气动力模块、水动力模块、系泊模块和系统运动模块构成。气动力模块采用叶素动量法;水动力模块采用一阶势流理论,通过边界元法求解;系泊模块采用悬链线模型,用Chebyshev多项式进行拟合计算。对于系统运动模块,采用Runge-Kutta法求解。对OC3-Hywind spar风机进行了建模,对各模块及耦合模型的进行对比研究,验证了此耦合计算方法的准确性。并利用该方法计算和分析了此风机的运动响应及其对风机功率的影响。 相似文献
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为更深入考查叶片刚度对风力机气弹响应的影响,对叶片截面的刚度矩阵中的主对角线刚度系数在稳态风和湍流风况下的风力机气弹响应的影响以及敏感性进行系统研究。气弹模型中的气动模块采用基于叶素动量理论,并采用几何精确梁理论对叶片的结构动力学响应进行仿真。选用美国可再生能源实验室(NREL)5 MW风力机组作为基准模型,调整叶片各截面刚度矩阵的主对角线刚度系数,利用敏感性影响因子评估刚度系数变化对叶片载荷的影响。结果表明:主对角线上挥舞方向的剪切刚度、挥舞弯曲刚度、摆振弯曲刚度、扭转刚度对气弹响应具有中高的敏感性。研究结果对掌握风力机气弹响应规律,发掘更深层次的风力机叶片设计方法提供了一定的指导意义。该方法能进一步扩展至研究叶片刚度对风力机机组气弹响应的敏感性研究。 相似文献
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Horizontal axis wind turbines operate under yawed conditions for a considerable period of time due to the power control mechanism or sudden changes in the wind direction. This in turn can alter the dynamic characteristics of a turbine blade because the flow over the rotor plane may trigger complicated induced velocity patterns. In this study, an aeroelastic analysis under yawed flow conditions is carried out to investigate the effects of yaw error on the blade behaviors and dynamic stability. A beam model including geometric nonlinearity coupled with unsteady aerodynamics based on a free-vortex wake method with the blade element theory is employed in the present study. The aerodynamic approach for a horizontal axis wind turbine blade under yawed flow conditions is verified through comparison with measurements. It is also shown that the present method gives slightly better results at high yaw angles than does the method previously published in the literature. The dynamic instabilities of a National Renewable Energy Laboratory 5 MW reference wind turbine have subsequently been investigated for various wind speeds and yaw angles. Observations are made that yaw effects induce considerable changes in airloads and blade structural behavior. Also, the aeroelastic damping values for this particular blade under yawed flow conditions can be reduced by up to approximately 33% in the worst case. Therefore, it is concluded that the impacts of yaw misalignments adversely influenced the dynamic aeroelastic stability of the horizontal axis wind turbine blade. 相似文献
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Modern offshore wind turbines are susceptible to blade deformation because of their increased size and the recent trend of installing these turbines on floating platforms in deep sea. In this paper, an aeroelastic analysis tool for floating offshore wind turbines is presented by coupling a high‐fidelity computational fluid dynamics (CFD) solver with a general purpose multibody dynamics code, which is capable of modelling flexible bodies based on the nonlinear beam theory. With the tool developed, we demonstrated its applications to the NREL 5 MW offshore wind turbine with aeroelastic blades. The impacts of blade flexibility and platform‐induced surge motion on wind turbine aerodynamics and structural responses are studied and illustrated by the CFD results of the flow field, force, and wake structure. Results are compared with data obtained from the engineering tool FAST v8. 相似文献
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Development of an aeroelastic code based on three‐dimensional viscous–inviscid method for wind turbine computations 下载免费PDF全文
Aerodynamic and structural dynamic performance analysis of modern wind turbines are routinely estimated in the wind energy field using computational tools known as aeroelastic codes. Most aeroelastic codes use the blade element momentum (BEM) technique to model the rotor aerodynamics and a modal, multi‐body or the finite‐element approach to model the turbine structural dynamics. The present work describes the development of a novel aeroelastic code that combines a three‐dimensional viscous–inviscid interactive method, method for interactive rotor aerodynamic simulations (MIRAS), with the structural dynamics model used in the aeroelastic code FLEX5. The new code, called MIRAS‐FLEX, is an improvement on standard aeroelastic codes because it uses a more advanced aerodynamic model than BEM. With the new aeroelastic code, more physical aerodynamic predictions than BEM can be obtained as BEM uses empirical relations, such as tip loss corrections, to determine the flow around a rotor. Although more costly than BEM, a small cluster is sufficient to run MIRAS‐FLEX in a fast and easy way. MIRAS‐FLEX is compared against the widely used FLEX5 and FAST, as well as the participant codes from the Offshore Code Comparison Collaboration Project. Simulation tests consist of steady wind inflow conditions with different combinations of yaw error, wind shear, tower shadow and turbine‐elastic modeling. Turbulent inflow created by using a Mann box is also considered. MIRAS‐FLEX results, such as blade tip deflections and root‐bending moments, are generally in good agreement with the other codes. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
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Assessment of a comprehensive aeroelastic tool for horizontal‐axis wind turbine rotor analysis 下载免费PDF全文
This paper presents the development of a computational aeroelastic tool for the analysis of performance, response and stability of horizontal‐axis wind turbines. A nonlinear beam model for blades structural dynamics is coupled with a state‐space model for unsteady sectional aerodynamic loads, including dynamic stall effects. Several computational fluid dynamics structural dynamics coupling approaches are investigated to take into account rotor wake inflow influence on downwash, all based on a Boundary Element Method for the solution of incompressible, potential, attached flows. Sectional steady aerodynamic coefficients are extended to high angles of attack in order to characterize wind turbine operations in deep stall regimes. The Galerkin method is applied to the resulting aeroelastic differential system. In this context, a novel approach for the spatial integration of additional aerodynamic states, related to wake vorticity and dynamic stall, is introduced and assessed. Steady‐periodic blade responses are evaluated by a harmonic balance approach, whilst a standard eigenproblem is solved for aeroelastic stability analyses. Drawbacks and potentialities of the proposed model are investigated through numerical and experimental comparisons, with particular attention to rotor blades unsteady aerodynamic modelling issues. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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An aeroelastic model for wind turbine blades derived from the unsteady Navier‐Stokes equations and a mode shape–based structural dynamics model are presented. For turbulent flows, the system is closed with the Spalart‐Allmaras turbulence model. The computation times for the aerodynamic solution are significantly reduced using the harmonic balance method compared to a time‐accurate solution. This model is significantly more robust than standard aeroelastic codes that rely on blade element momentum theory to determine the aerodynamic forces. Comparisons with published results for the Caradonna‐Tung rotor in hover and the classical AGARD 445.6 flutter case are provided to validate the aerodynamic model and aeroelastic model, respectively. For wind turbines, flutter of the 1.5 MW WindPACT blade is considered. The results predict that the first flapwise and edgewise modes dominate flutter at the rotor speeds considered. 相似文献
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Downwind wind turbine blades are subjected to tower wake forcing at every rotation, which can lead to structural fatigue. Accurate characterisation of the unsteady aeroelastic forces in the blade design phase requires detailed representation of the aerodynamics, leading to computationally expensive simulation codes, which lead to intractable uncertainty analysis and Bayesian updating. In this paper, a framework is developed to tackle this problem. Full, detailed aeroelastic model of an experimental wind turbine system based on 3‐D Reynolds‐averaged Navier‐Stokes is developed, considering all structural components including nacelle and tower. This model is validated against experimental measurements of rotating blades, and a detailed aeroelastic characterisation is presented. Aerodynamic forces from prescribed forced‐motion simulations are used to train a time‐domain autoregressive with exogenous input (ARX) model with a localised forcing term, which provides accurate and cheap aeroelastic forces. Employing ARX, prior uncertainties in the structural and rotational parameters of the wind turbine are introduced and propagated to obtain probabilistic estimates of the aeroelastic characteristics. Finally, the experimental validation data are used in a Bayesian framework to update the structural and rotational parameters of the system and thereby reduce uncertainty in the aeroelastic characteristics. 相似文献
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The formulation and quality of a computationally efficient model of offshore wind turbine surface foundations are examined. The aim is to establish a model, workable in the frequency and time domain, that can be applied in aeroelastic codes for fast and reliable evaluation of the dynamic structural response of wind turbines, in which the geometrical dissipation related to wave propagation into the subsoil is included. Based on the optimal order of a consistent lumped-parameter model obtained by the domain-transformation method and a weighted least-squares technique, the dynamic vibration response of a 5.0 MW offshore wind turbine is evaluated for different stratifications, environmental conditions and foundation geometries by the aeroelastic nonlinear multi-body code HAWC2. Analyses show that a consistent lumped-parameter model with three to five internal degrees of freedom per displacement or rotation of the foundation is necessary in order to obtain an accurate prediction of the foundation response in the frequency and time domain. In addition, the required static bearing capacity of surface foundations leads to fore–aft vibrations during normal operation of a wind turbine that are insensitive to wave propagating in the subsoil—even for soil stratifications with low cut-in frequencies. In this regard, utilising discrete second-order models for the physical interpretation of a rational filter puts special demands on the Newmark β-scheme, where the time integration in most cases only provides a causal response for constant acceleration within each time step. 相似文献
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针对风力机叶片,建立其结构动力学方程,推导分析了叶片旋转所产生的振动速度及其对来流的影响。基于BEM(Blade Element Momentum)理论,在风力机空气动力学基础上,建立了风力机的气动耦合分析模型。应用该模型,对某2MW风力机进行了计算分析,得到了叶片在额定工作风速下的振动变形、速度、加速度以及叶片沿展向的变形和载荷分布。充分考虑叶片的结构振动特性与来流风速的耦合效应,使得风力机空气动力学特性模型更加准确,对于风力机的设计和分析具有重要意义。 相似文献