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Potential and challenges of wind measurements using met-masts in complex topography for bridge design: Part II – Spectral flow characteristics
Journal of Wind Engineering and Industrial Aerodynamics ( IF 4.8 ) Pub Date : 2021-04-02 , DOI: 10.1016/j.jweia.2021.104585
Zakari Midjiyawa , Etienne Cheynet , Joachim Reuder , Hálfdán Ágústsson , Trond Kvamsdal

This study quantifies the influence of the local topography on sonic anemometer measurements mounted on tall met-masts deployed in Norwegian fjords. This assessment is done by analysing the second-order structure of turbulence in the frequency space. The objective is to evaluate how the data collected by these masts can help with the design of future fjord-crossing bridges. Using measurements from eight masts deployed in three different fjords, spectral characteristics common to the different locations were identified. Among the characteristics investigated, the one-point velocity spectra and the vertical coherence of turbulence are of special interest for bridge design. Using only situations with a mean wind speed of 12 ​m ​s−1 and above and rather stationary flow conditions, the remaining wind direction sectors could be classified into two main groups: those with a long fetch over smooth topography and those with a rough heterogeneous terrain upstream of the masts. It was found that if the velocity spectra are normalized by an appropriate estimate of the friction velocity, surface-layer scaling may be applicable in Norwegian fjords, at least under near-neutral conditions. The velocity spectra, estimated with long upstream fjord fetches have characteristics consistent with those collected in coastal and offshore environments. The Davenport model showed limited capabilities in describing the co-coherence of turbulence on vertical separations. The dependency of the Davenport decay coefficient with the height and spatial separation is highlighted and may be substantial in mountainous terrain. Although the spectral flow characteristics estimated on the shore of fjords are relevant for the design of fjord-crossing bridge towers, they may not easily be extrapolated for the modelling of the turbulent flow in the middle of the fjord. Nevertheless, they are still valuable to complement computational fluid dynamic simulations, wind tunnel tests, or remote sensing of wind across the fjord.



中文翻译:

在复杂的地形中使用气象站进行桥梁设计进行风测量的潜力和挑战:第二部分–光谱流特性

这项研究量化了局部地形对安装在挪威峡湾高桅杆上的声速计测量的影响。该评估是通过分析频率空间中湍流的二阶结构来完成的。目的是评估这些桅杆收集的数据如何帮助设计未来的峡湾跨海大桥。使用在三个不同峡湾中部署的八个桅杆的测量结果,确定了不同位置共有的光谱特征。在研究的特性中,单点速度谱和湍流的垂直相干性对于桥梁设计特别重要。仅使用平均风速为12 m s -1的情况除了上面提到的平稳的流动条件外,其余的风向扇区可以分为两大类:在平滑地形上具有较长获取时间的扇区,以及在桅杆上游具有不均匀地形的粗糙扇区。已经发现,如果通过对摩擦速度的适当估计来对速度谱进行归一化,则至少在接近中性的条件下,在挪威峡湾中可以应用表层缩放。用长的上游峡湾提取物估算的速度谱具有与在沿海和近海环境中收集的速度谱一致的特征。Davenport模型在描述垂直分离中湍流的相干性方面显示出有限的能力。Davenport衰减系数与高度和空间间隔的相关性已突出显示,在山区地形中可能很大。尽管在峡湾岸边估计的频谱流动特性与跨峡湾大桥塔的设计有关,但对于峡湾中部的湍流建模,可能不容易将其推断出来。尽管如此,它们仍然是补充计算流体动力学模拟,风洞测试或峡湾风的遥感的有价值的工具。

更新日期:2021-04-02
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