Nonlinear analysis of flow-induced instabilities of wind turbine blades using theoretical models and supported by experimental data

主要研究人员：Yahya Modarres-SaderhiNumber：1437988标题：使用理论模型和实验数据支持的风力机叶片流动不稳定性的非线性分析机构：马萨诸塞大学阿默尔分校(University of Massachusetts，Amherst)越来越多地将风力发电场设在离岸海域，以获取这种可再生能源。风力发电场内的各个风力涡轮机可以提取的可用能量与涡轮机转子叶片的掠过面积成正比，这就产生了设计、制造和商业使用更长、更细的叶片的强大动力。这一趋势是由经济因素推动的--海上风电场的安装成本远远高于陆上风电场，因此增加每台安装的风力涡轮机的发电量对经济高效的海上风能至关重要。然而，随着叶片变得更长和更细，它们变得更容易受到各种流动诱导的不稳定性的影响。一种特别麻烦的不稳定性是叶片与风的相互作用引起的不必要的叶片振荡或颤动。这种不稳定的行为可能会导致叶片的灾难性故障。这一限制对海上风力涡轮机的完整性及其可靠运行的能力构成了威胁。在目前的研究中，将使用基于非线性分析技术的先进计算模型来研究风力机叶片的流动不稳定性，以便更好地了解这些不稳定性，并为未来风力机叶片的设计提供指导。作为拟议活动的一部分，首席调查员将在北美风能学院(NAWEA)组织一次关于近海风能的会议，开发针对初中生和高中生的关于风力涡轮机的YouTube演示，并就同一主题向当地高中生进行演示。本研究的目标是开发一种非线性、全耦合的连续流固耦合模型，用于柔性和旋转的风力机叶片。该模型将用于研究细长叶片的流致不稳定性，这些叶片有望用于未来的岸上风力涡轮机。风力机叶片本质上是一个三维的非线性系统。然而，目前用于风力机叶片不稳定性分析的方法已将叶片建模为二维线性系统，以绕过与三维非线性系统建模相关的困难。然而，随着叶片变得更长、更细，需要更全面的型号。所提出的柔性叶片和旋转叶片的非线性模型将考虑叶片形状和截面的变化，以及弯曲和扭转特性。几何、流动相关和流固耦合的非线性将被嵌入到模型中。将进行一系列全面的风洞实验来验证该模型。验证后的模型将被用来提供风力机叶片流动不稳定性的基本理解。这种方法还可以研究高度非线性流固耦合作用下沿长度方向具有非均匀特性的柔性结构的非线性不稳定性，从而对非线性流固耦合系统的物理基础有更广泛的理解。关于教育和更广泛的影响，首席研究员将在北美风能学院(NAWEA)组织一次关于近海风能的会议。外展活动包括开发针对初中生和高中生的关于风力涡轮机的YouTube演示，以及针对当地高中生的同一主题的演示。

Principal Investigator: Yahya Modarres-SadeghiNumber: 1437988 Title: Nonlinear analysis of flow-induced instabilities of wind turbine blades using theoretical models and supported by experimental dataInstitution: University of Massachusetts, AmherstIncreasingly, wind farms for the production electricity are being sited off shore to harvest this renewable energy resource. The available energy that individual wind turbines within the wind farm may extract is proportional to the swept area of the turbine rotor blades, creating a powerful incentive to design, manufacture, and commercially use longer and more slender blades. This trend is driven by economics - wind farm installation costs are substantially higher offshore than onshore, and so increased energy production per installed wind turbine is crucial for cost-effective offshore wind energy. However, as blades become longer and more slender, they become more susceptible to various flow induced instabilities. A particularly troublesome instability is the unwanted blade oscillations, or flutter, caused by the interaction of the blade with the wind. This unstable behavior can lead to catastrophic failure of the blades. This limitation poses a threat to the integrity of offshore wind turbines and their ability to reliably operate. In the current research, flow-induced instabilities of wind turbine blades will be studied using advanced computational models based on a technique called nonlinear analysis in order to better understand these instabilities and develop guidelines for the design of future wind turbine blades. As part of the proposed activities, the principal investigator will organize a session at the North American Wind Energy Academy (NAWEA) on Offshore Wind Energy, develop YouTube presentations on wind turbines targeted to middle and high school students, and give demonstrations to local high school students on the same topic. Technical DescriptionThe goal of this research is to develop a nonlinear, fully-coupled continuous fluid-structure interaction model for flexible and rotating wind turbine blades. This model will be used to study flow-induced instabilities for long and slender blades that are anticipated to be used in future shore wind turbines. A wind turbine blade is an inherently three-dimensional and nonlinear system. Nevertheless, current approaches for wind turbine blade instability analysis have modeled the blades as two-dimensional, linear systems in order to bypass the difficulties associated with three-dimensional, nonlinear system modeling. However, as blades become longer and more slender, the need for more comprehensive models is necessary. The proposed nonlinear model for flexible and rotating blades will account for varying blade shapes and cross-sections, as well as bending and torsional properties. Geometric, flow-related and fluid-structure interaction nonlinearities will be embedded into the model. A comprehensive series of wind tunnel experiments will be conducted to validate this model. The validated model will then be used to provide a fundamental understanding of flow-induced instabilities of wind turbine blades. This approach will also enable the study of nonlinear instability of flexible structures with non-uniform properties along their length under highly nonlinear interaction with flow, and thus provide a broader understanding of the physics underlying nonlinear fluid-structure interaction systems. With respect to education and broader impacts, the principal investigator will organize a session at the North American Wind Energy Academy (NAWEA) on Offshore Wind Energy. Outreach activities include development of YouTube presentations on wind turbines targeted to middle and high school students, and demonstrations to local high school students on the same topic.