Cao Huijing, Zhou Teng, Zhang Yinan, Zhang Mingming
Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100190, China.
School of Mechanical Engineering and Automation, Harbin Institute of Technology, Shenzhen 518055, China.
J Acoust Soc Am. 2022 Feb;151(2):1211. doi: 10.1121/10.0009570.
Trailing edge (TE) serrations are widely used as an effective passive control method to reduce the turbulent TE noise from wind turbine blades. Other than the acoustic effects, the aerodynamic performance of serrations is also an important issue that should be considered, since it determines the power output of the blade. To this end, the far-field sound pressure level, flow field, and aerodynamic force of the serrated airfoil were measured in an anechoic wind tunnel, and the lift increase and noise reduction effects of the TE serrations were comprehensively evaluated. The result showed that the presence of TE serrations could achieve noise reduction by about 2 dB at the low-to-moderate frequency range at small angles of attack, and meanwhile it could suppress the fluctuation of aerodynamic forces. In addition, the proper orthogonal decomposition method was deployed to decompose the wake flow into various vortex structures with different portions of turbulent kinetic energy so as to reveal the noise reduction mechanism of the serrated TE. The result suggested that TE serrations could effectively inhibit large-scale vortex structures that shed from the boundary layer on the suction side, thereby achieving noise reduction around the vortex shedding frequency.
trailing edge (TE) serrations are widely used as an effective passive control method to reduce the turbulent TE noise from wind turbine blades. Other than the acoustic effects, the aerodynamic performance of serrations is also an important issue that should be considered, since it determines the power output of the blade. To this end, the far-field sound pressure level, flow field, and aerodynamic force of the serrated airfoil were measured in an anechoic wind tunnel, and the lift increase and noise reduction effects of the TE serrations were comprehensively evaluated. The result showed that the presence of TE serrations could achieve noise reduction by about 2 dB at the low-to-moderate frequency range at small angles of attack, and meanwhile it could suppress the fluctuation of aerodynamic forces. In addition, the proper orthogonal decomposition method was deployed to decompose the wake flow into various vortex structures with different portions of turbulent kinetic energy so as to reveal the noise reduction mechanism of the serrated TE. The result suggested that TE serrations could effectively inhibit large-scale vortex structures that shed from the boundary layer on the suction side, thereby achieving noise reduction around the vortex shedding frequency.
后缘锯齿广泛用作一种有效的被动控制方法，以降低风力涡轮机叶片的后缘湍流噪声。除了声学效应外，锯齿的空气动力学性能也是一个应考虑的重要问题，因为它决定了叶片的功率输出。为此，在消声风洞中测量了锯齿翼型的远场声压级、流场和空气动力，并综合评估了后缘锯齿的升力增加和降噪效果。结果表明，在后缘存在锯齿的情况下，在小攻角的低至中频范围内可实现约2dB的降噪，同时还能抑制空气动力的波动。此外，采用适当正交分解方法将尾流分解为具有不同湍动能部分的各种涡旋结构，以揭示锯齿后缘的降噪机制。结果表明，后缘锯齿可以有效抑制从吸力面边界层脱落的大尺度涡旋结构，从而在涡旋脱落频率附近实现降噪。
