Aerodynamic Instabilities of Thin-walled Structures for Driving Novel Energy Harvesters - Numerical Simulation Method, Physical Effects and Analytical Model

颤振等气动弹性现象对于飞机机翼和桥梁等轻型工程结构的设计具有重要意义。这些线状结构的横截面大致保持其形状，并且它们的设计不会颤动。相比之下，能量收集的新概念是基于从经历弯曲的气动弹性不稳定薄壁结构中提取能量。它们被设计成具有较低的颤振起始风速，并且它们表现出大的横截面变形。影响这些元件动态响应的重要因素是大气湍流和几何非线性。在实际应用中感兴趣的参数是起始风速、可提取能量和结构需求。为了详细研究这类结构和许多其他类似结构的基本流固相互作用机理，量化影响性能的重要参数，并促进系统的优化，需要分析模型。本文发展了一种基于涡旋质点方法(VPM)的数值模拟方法，该方法将几何非线性结构动力学有限元格式与VPM边界元方法的新扩展相结合，从而考虑了固体界面几何的大变形。此外，应应用最新的大气湍流模拟发展，以便能够考虑自然风的阵风。该方法将以一种通用的方式开发和实施，以允许将其应用于其他问题，例如轻型屋顶结构。这里，以新型电磁能量采集器的概念作为参考对象。为了验证仿真方法的有效性，样机模型将在风洞中进行测试。试验过程中将对结构的动力响应进行详细测量。然后，将使用该数值模型来量化与收割机的效率和结构需求相关的方面。最后，对Scanlan导数的概念进行了扩展，建立了一个新的薄壁结构自诱导流体动力定量化分析模型。该模型将允许简化的分析稳定性分析，并便于研究影响系统行为的参数。

Aeroelastic phenomena such as flutter are of major relevance for the design of light engineering structures such as aircraft wings and bridges. These line-like structures have cross sections that approximately retain their shape and they are designed not to flutter. In contrast, novel concepts of energy harvesting are based on extracting energy from aeroelastically unstable thin-walled structures that undergo bending. These are designed to have a low flutter onset wind speed and they exhibit large cross sectional deformations. Important factors influencing the dynamic response of these elements are atmospheric turbulence and geometric nonlinearities. Parameters of interest in the context of practical applications are onset wind speed, extractable energy and structural demand. In order to study the underlying fluid-structure interaction mechanisms of such and many other similar structures in detail, to quantify the important parameters influencing the behaviour and to facilitate an optimisation of the system, analysis models are required. Here, a numerical simulation method on the basis of Vortex Particle Methods (VPM) shall be developed, which couples a geometrically nonlinear structural dynamics Finite Element formulation with a new extension of the Boundary Element Method of the VPM, thus accounting for large deformations of the solid interface geometry. Further, recent developments for modelling atmospheric turbulence shall be applied, in order to be able to account for the gustiness of the natural wind. The method will be developed and implemented in a generalised manner that allows the application to other problems such as light roof structures. Here, the concept of a new electromagnetic energy harvester shall be used as a reference object. Prototype models will be tested in the wind tunnel in order to validate the simulation methods. The dynamic response of the structure will be measured in detail during the tests. The numerical model will then be used to quantify relevant aspects with regard to efficiency of and structural demand on the harvester. Finally, a new analytical model for the quantification of the self-induced fluid dynamic forces on thin-walled structures shall be developed, which extends the concept of Scanlan Derivatives. This model would allow simplified analytical stability analyses and facilitate studies of parameters influencing the system behaviour.