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持续增长以从风中提取更多的能量。这种趋势导致更灵活的叶片更容易受到流动引起的不稳定性的影响，这可能导致突然和灾难性的故障。这些动态不稳定性的开始可以通过系统中的固有不确定性来改变，并且危险地接近风力涡轮机的设计操作速度。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涡轮机叶片的成功操作是至关重要的。本项目的目标是研究和理解主动控制大型风力涡轮机叶片非线性流致不稳定性的适当方法，同时考虑其固有的随机性。该项目将支持设计和操作更大，更灵活的风力涡轮机叶片的能力，这将最终增加能源捕获并降低海上风能的能源成本。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。本研究的成果将通过为不同课程创建新模块、举办高中课程和增加学生的研究机会等方式在不同层面上传播。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横截面以及弯曲和扭转特性。我们将使用这个非线性模型来研究一些非确定性的系统参数对流动引起的不稳定性的发作的影响，使用摄动方法以及随机微积分，并研究策略，积极控制这些流动引起的不稳定性，使用先进的分岔控制，概率鲁棒性和多变量鲁棒控制。该项目的智力价值在于一个统一的方法，以促进大型风力涡轮机系统的控制策略的基本理解和分析，其中涉及到一个灵活的结构（叶片）和非定常流的相互作用。这些系统包含来自结构、围绕其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。这项研究是变革性的，因为它提供了基本的洞察力的基础物理和控制的非线性随机流体结构相互作用系统的非均匀属性，包括未来的风力涡轮机叶片，通过结合几个不同领域的专业知识。

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.