This experimental study investigates the effect of biologically inspired finlets on the reduction of trailing-edge noise of a NACA 0012 airfoil. At a chord-based Reynolds number of 400,000, the far-field noise measurements show that the finlets are capable of reducing the trailing-edge noise effectively from 1000 to 4000 Hz with up to 6 dB reduction, for effective angles of attack from 0 to 8 deg. By correlating the far-field noise to the boundary-layer measurements, an optimal finlet height to boundary-layer thickness ratio to achieve the highest noise reduction is discussed. Static pressure and dynamic pressure fluctuations are examined, particularly within the finlet-treated area, to capture the flow dynamics through the treatments. The unsteady surface pressure fluctuation spectra show strong reduction at frequencies higher than 1000 Hz in the finlet wake, complying with the far-field measurements. Both the auto- and cross-correlation results of the unsteady surface pressure reveal the formation of large-scale turbulence at the entrance and toward the exit of the finlets. Moreover, they suggest that the formation and subsequent mixing of these large-scale structures with the boundary layer can be beneficial to reducing the unsteady surface pressure fluctuations. The findings will be useful to potential optimization of the finlets.

本实验研究调查了受生物启发的翅片对降低 NACA 0012 机翼后缘噪声的影响。在基于弦的雷诺数为 400,000 时，远场噪声测量表明，对于从 0 到 0 8 度。通过将远场噪声与边界层测量值相关联，讨论了实现最高噪声降低的最佳翅片高度与边界层厚度比。检查静压和动压波动，特别是在鳍片处理区域内，以捕捉通过处理的流动动态。非定常表面压力波动谱在小鳍尾流中高于 1000 Hz 的频率处显示出强烈降低，符合远场测量。非定常表面压力的自相关和互相关结果都揭示了在翅片入口和出口处形成了大规模湍流。此外，他们认为这些大尺度结构与边界层的形成和随后的混合有利于减少不稳定的表面压力波动。研究结果将有助于鳍的潜在优化。他们认为，这些大型结构与边界层的形成和随后的混合有利于减少不稳定的表面压力波动。研究结果将有助于鳍的潜在优化。他们认为，这些大型结构与边界层的形成和随后的混合有利于减少不稳定的表面压力波动。研究结果将有助于鳍的潜在优化。