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.

受到涡激振动的细长结构在锁定范围内经历气动弹性相互作用，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统一的气动行为。阻尼作为振荡的函数，这也反映在考虑侧风作用的细长结构的编码方法中，该证据首先适用于振荡幅度的最大值，此外，关于疲劳强度分析的载荷过程建模，理论缺陷导致疲劳寿命的预测与其实际值之间存在更大的偏差。该研究项目旨在开发一种模型来预测疲劳寿命。整个锁定范围内的振荡幅度，为疲劳过程建模奠定了基础，应使用强制振动测试技术。风速为与振荡频率相关，从而探索实验中的共振区域，这样就可以确定气动阻尼的行为。2）受迫振荡的幅度包括斯克鲁顿数的影响。考虑到这一点，必须澄清，在大振荡的情况下，是否会出现振荡的极限值，即使在 Scruton 数越来越小的情况下也不能超过该极限值，或者如果3) 湍流强度通过扩展其谱带宽并因此扩大速度范围来影响激发过程的谱内容，从而更频繁地发生共振。气动弹性涡激振动的计算是基于该实验背景而开发的，该模型通过自由振动的风洞测试进行了实验验证。在时域中，根据斯克鲁顿数的值，研究了锁定范围（包括其上升至最大振荡以及其从共振中下降），间歇性（从数学上讲是准周期）振荡以占主导地位的随机性发生。也需要对它们进行建模，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。在实际承载行为的情况下进行气动弹性风洞试验的方法，特别是考虑到振型。