论文标题
自振荡的尾随褶皱的不同几何形状对空运自噪声的影响
Effect of different geometries of self-oscillating trailing-edge flaplets on aerofoil self-noise
论文作者
论文摘要
本文介绍了标准NACA 0012航空架的声学研究，并附着在后缘上附加了其他自我振荡的被动襟翼。在勃兰登堡理工大学的AneChoic风洞中进行了不同几何形状的测试，基于和弦的雷诺数字，$ re_c = 100,000-900,000 $，在三个几何角度的攻击角度$α_g= 0^\ circ，10^\ circ，10^\ circc，10^\ circver $ $ 15^^^^^\ $ $ 15^\ circ。据观察，所有襟翼构型都会降低音调噪声，并且降低该噪声组件的关键几何参数是褶皱的宽度。经过测试的最狭窄配置几乎完全消除了音调噪声，从而导致整个$ re_c $范围$α_g= 10^\ circ $的平均总体音压水平降低了9 dB。还可以观察到，在低频制度中，可以通过调整振荡褶皱的固有频率来实现进一步的降噪。因此，当弹奏的固有频率增加时，噪声光谱中的频率范围会移至较高的频率，反之亦然。因此，我们展示了一种新颖的方法，可以针对被动驾驶自噪声取消的特定频率。
This paper presents an acoustic study of a standard NACA 0012 aerofoil with additional self-oscillating passive flaplets attached to the trailing edge. The tests with varying geometries of the flaplets were conducted in the anechoic wind tunnel at Brandenburg University of Technology, at chord based Reynolds numbers, $Re_c = 100,000 - 900,000$ at three geometric angles of attack $α_g = 0^\circ, 10^\circ$ and $15^\circ$. It was observed that all flaplet configurations reduce tonal noise and that the key geometric parameter to reduce this noise component is the width of the flaplets. The narrowest configuration tested almost completely removed the tonal noise, leading to an average overall sound pressure level reduction of up to 9 dB across the entire $Re_c$ range at $α_g = 10^\circ$. It was also observed that, in the low frequency regime, a further noise reduction can be achieved by tuning the natural frequency of the oscillating flaplets. The thereby affected frequency range in the noise spectrum moves to higher frequencies when the natural frequency of the flaplets is increased and vice versa. Hence we show a novel way to target specific frequencies in passive aerofoil self-noise cancellation.
