Modelling the aeroelastic response of slender structures to vortex-induced vibrations for fatigue analysis

模拟细长结构对涡激振动的气动弹性响应以进行疲劳分析

• 批准号: 426322127
• 负责人: Dr.-Ing. Francesca Lupi
• 金额: --
• 依托单位: Arbeitsgruppe Windingenieurwesen und Strömungsmechanik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/426322127?language=en
• 关键词: Modelling; aeroelastic; response; slender; structures

Slender structures subjected to vortex-induced vibrations experience an aeroelastic interaction in the lock-in range. The negative aerodynamic damping is the governing parameter for the onset of self-induced vibrations. However, available literature models still lack of a unified behaviour of the aerodynamic damping as a function of the oscillation. This is also reflected in codified methods to design slender structures in view of cross-wind actions. This evidence applies firstly for the maxima of the oscillation amplitudes, i.e. the maxima of the structural stresses. Additionally, concerning modelling of load processes for the analysis of fatigue strength, theoretical deficiencies cause even larger deviations between the prediction of fatigue life and its actual value.The research project aims to develop a model to predict the oscillation amplitudes throughout the lock-in range, thereby laying the foundation for modelling of fatigue processes. The starting point is the experimental investigation in a wind tunnel. The forced-vibration testing technique shall be used. The following parameters are considered:1) The wind velocity is varied in relation to the oscillation frequency, thereby exploring the resonance zone in the experiment. In this way, it is possible to determine the behaviour of the aerodynamic damping.2) The amplitude of the forced oscillation includes the effect of the Scruton number. In this regard, it has to be clarified if, in case of large oscillations, a limiting value of the oscillation occurs, which cannot be exceeded even in case of increasingly smaller Scruton numbers, or if the boundaries of the aerodynamic damping are asymptotically approached. 3) The turbulence intensity influences the spectral content of the excitation process by extending its spectral bandwidth and consequently enlarging the velocity range, in which lock-in occurs. As a result, resonance happens more often.A model for the calculation of the aeroelastic, vortex-induced vibration is developed based on this experimental background. The model is validated experimentally through wind tunnel tests in free-vibrations. Additionally, through these tests, the whole lock-in range – including its rises to the largest oscillation as well its drops from resonance – is investigated. In time domain, depending on the value of the Scruton number, intermittent - mathematically speaking quasi-periodic - oscillations occur with either a predominant stochastic or a harmonic character. They need to be modelled as well, in order to determine the effect on the fatigue life of both full resonance and intermittent situations throughout the whole resonance zone. Finally, the whole concept will be verified by means of aeroelastic wind tunnel tests in case of a realistic load bearing behaviour, especially in view of the mode shape.

细长结构在涡激振动作用下，在锁定范围内会发生气动弹性干扰。负气动阻尼是自激振动发生的控制参数。然而，现有的文献模型仍然缺乏一个统一的行为的气动阻尼作为一个功能的振荡。这也反映在考虑侧风作用的细长结构设计的规范化方法中。这一证据首先适用于振幅的最大值，即结构应力的最大值。此外，在疲劳强度分析的载荷过程建模方面，由于理论上的不足，导致疲劳寿命的预测值与实际值之间存在较大的偏差。本研究项目旨在开发一个模型，预测整个锁定范围内的振荡幅度，从而为疲劳过程建模奠定基础。本文的出发点是在风洞中进行的实验研究。应采用强制振动试验技术。考虑以下参数：1） 风速的变化与振荡频率，从而探索在实验中的共振区。通过这种方式，可以确定空气动力阻尼的行为。2） 强迫振荡的振幅包括斯克鲁顿数的影响。在这方面，必须澄清的是，在大振荡的情况下，是否出现振荡的极限值，该极限值即使在越来越小的斯克鲁顿数的情况下也不能被超过，或者如果空气动力阻尼的边界渐近地接近。第三章 湍流强度通过扩展其光谱带宽并因此扩大发生锁定的速度范围来影响激发过程的光谱内容。在此基础上，建立了一个气动弹性涡激振动的计算模型。该模型通过自由振动风洞试验进行了验证。此外，通过这些测试，整个锁定范围-包括其上升到最大振荡以及其从谐振下降-进行了研究。在时域中，取决于斯克鲁顿数的值，间歇性-数学上讲是准周期性-振荡以主要的随机或谐波特征发生。它们也需要建模，以确定整个共振区的完全共振和间歇情况对疲劳寿命的影响。最后，整个概念将通过气动弹性风洞试验进行验证，特别是考虑到模态的实际承载性能。