Collaborative Research: Active Control of Nonlinear Flow-Induced Instability of Wind Turbine Blades under Stochastic Perturbations

风力涡轮机叶片的长度继续增长，以从风中提取更多能量。这一趋势导致叶片更灵活，更容易受到流动引起的不稳定性的影响，这可能会导致突然的灾难性故障。这些动态不稳定的开始可以被系统中固有的不确定性改变，并且危险地接近风力涡轮机的设计运行速度。这对系统的完整性构成了威胁。能够控制这些不稳定性对于未来风力机叶片的成功运行至关重要。本项目的目标是研究和理解适当的方法，以积极控制大型风力机叶片的非线性流致不稳定性，考虑到其固有的随机性质。该项目将支持设计和运营更大、更灵活的风力涡轮机叶片的能力，这最终将增加能量捕获并降低海上风能的成本。这项研究是及时的，因为美国目前的能源计划强烈强调需要从海上风能等来源生产替代能源。这项研究的成果将通过为不同的课程创建新的模块，举办高中课程，以及增加学生的研究机会，在不同的层面上传播。本研究将考虑柔性旋转叶片的全耦合连续流固耦合模型，考虑不同的叶片形状和截面，以及弯曲和扭转特性。我们将使用这个非线性模型，利用摄动方法和随机微积分来研究一些不确定系统参数对流动诱导不稳定开始的影响，并利用分叉控制、概率鲁棒性和多变量鲁棒控制的进展来研究主动控制这些流动诱导不稳定的策略。该项目的学术价值在于采用了一种统一的方法来促进对大型风力涡轮机系统控制策略的基本理解和分析，这些策略涉及柔性结构(叶片)和非定常流动的相互作用。这些系统包含来自结构、其周围的流体流动以及流体与结构之间的相互作用的组合非线性。这项研究具有变革性，因为它结合了几个不同的专业领域，为具有非均匀特性的非线性随机流-结构相互作用系统的基本物理和控制提供了基本见解，包括未来的风力涡轮机叶片。

Wind turbine blades continue to grow in length to extract more energy from the wind. This trend results in more flexible blades that are more susceptible to flow-induced instabilities, which can lead to sudden and catastrophic failures. The onset of these dynamic instabilities can be altered by the inherent uncertainties in the system, and is dangerously close to the wind turbine's designed operational speed. This poses a threat to the integrity of the system. Being able to control these instabilities is critical for the successful operation of future wind turbine blades. The goal of this project is to examine and understand appropriate methodologies to actively control nonlinear flow-induced instabilities of large wind turbine blades, considering their inherent stochastic nature. This project will support the ability to design and operate larger, more flexible wind turbine blades, which will eventually increase energy capture and reduce the cost of energy offshore wind. This research is timely since the current energy plan of the United States strongly emphasizes the need for alternative energy production from sources such as offshore wind energy. The findings of this research will be disseminated at different levels by creating new modules for different courses, hosting high school classes, and increasing research opportunities for students.This research will consider a fully-coupled continuous fluid-structure interaction model of the flexible, rotating blades, accounting for varying blade shapes and cross-sections, as well as bending and torsional properties. We will use this nonlinear model to examine the effect of a number of non-deterministic system parameters on the onset of flow-induced instabilities, using perturbation methods as well as stochastic calculus, and to investigate strategies to actively control these flow-induced instabilities using advances in bifurcation control, probabilistic robustness and multivariable robust control. The Intellectual Merit of this project lies in a unified methodology to advance the fundamental understanding and analysis of control strategies for large wind-turbine systems, which involve the interaction of a flexible structure (the blade) and unsteady flow. These systems contain combined nonlinearities from the structure, the fluid flow around it, and the interaction between the fluid and the structure. This research is transformative because it provides fundamental insights into the underlying physics and control of nonlinear stochastic fluid-structure interaction systems with non-uniform properties, including future wind turbine blades, by combining several different areas of expertise.