Owing to the rapid development of the offshore wind power technology and increasing capacity of wind turbines, vertical-axis wind turbines (VAWTs) have experienced a great development. Nevertheless, the VAWT wake effect, which affects the power generation efficiency and rotor fatigue life, has not been thoroughly understood. In this study, the mid-span wake measurements on a VAWT in six different configurations were conducted. This study aimed to investigate the effect of solidity on near wake instability of vertical-axis wind turbine. By using the wavelet analysis method to analyse the measured velocity (or pressure) time series signals on a multi-scale and with multi-resolution, the dynamic characteristics of the coherent vortex structures in the wake evolution process were determined. The results show that with increasing solidity, the VAWT wake develops into a bluff body wake mode. In addition, a characteristic frequency that is lower than the low-frequency large-scale vortex shedding frequency occur. The wavelet transform was used to decompose and reconstruct the measured data, and the relationship between the low-frequency large-scale vortex shedding and lower frequency pulsation was established. The results provide important data for numerical modelling and new insights into the physical mechanism of the VAWT wake evolution into a bluff body wake.

中文翻译：

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强度对垂直轴风力发电机近尾不稳定性影响的风洞试验

由于海上风力发电技术的飞速发展和风力涡轮机容量的增加，垂直轴风力涡轮机（VAWT）得到了长足的发展。然而，尚未完全了解影响发电效率和转子疲劳寿命的VAWT尾流效应。在这项研究中，在六种不同配置的VAWT上进行了中跨唤醒测量。这项研究旨在调查强度对垂直轴风力发电机近尾不稳定性的影响。通过使用小波分析方法以多尺度和多分辨率分析测得的速度（或压力）时间序列信号，确定了尾流演化过程中相干涡结构的动力学特性。结果表明，随着坚固性的提高，VAWT尾流发展为虚张声势的身体尾流模式。另外，出现了比低频大尺度涡旋脱落频率低的特征频率。利用小波变换对测量数据进行分解和重构，建立了低频大涡旋脱落与低频脉动的关系。结果为数值建模和对VAWT尾流演变成钝体尾流的物理机理提供了新的见解。建立了低频大涡旋脱落与低频脉动的关系。结果为数值建模和对VAWT尾流演变成钝体尾流的物理机理提供了新的见解。建立了低频大涡旋脱落与低频脉动的关系。结果为数值建模和对VAWT尾流演变成钝体尾流的物理机理提供了新的见解。