Analytic solution for aerodynamic noise generated by plates with spanwise-varying trailing edges
Analytic solution for aerodynamic noise generated by plates with spanwise-varying trailing edges
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DOI：
10.1017/jfm.2018.431
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发表时间：
2018-06
影响因子：
3.7
通讯作者：
Lorna J. Ayton
中科院分区：
文献类型：
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作者：
Lorna J. Ayton
本文给出了定常均匀背景流中非定常壁压阵风与展向可变后缘干扰产生的气动噪声的解析解。粘性和非线性效应被忽略。Wiener-Hopf方法与非正交坐标变换和分离变量结合使用，以允许分析进展。该解是在展向坐标系中采用定制的模态展开法得到的;然而，只有1000多个模态被截断，因此远场噪声可以快速评估。该解决方案提供了深入了解背后的潜在机制，减少噪音的板与锯齿后缘相比，那些直边。噪声降低背后的两种机制是在远场中增加的相消干涉，以及声能从低截止模式到较高截止模式的重新分布。五种不同的测试情况下的后缘几何形状被认为是。解析解确定了哪些几何结构在不同的频率范围内最有效：促进相消干涉的几何结构在低频下最好，而促进能量重新分布的几何结构在高频下更好。
This paper presents an analytic solution for aerodynamic noise generated by an unsteady wall pressure gust interacting with a spanwise-variable trailing edge in a background steady uniform flow. Viscous and nonlinear effects are neglected. The Wiener–Hopf method is used in conjunction with a non-orthogonal coordinate transformation and separation of variables to permit analytical progress. The solution is obtained in terms of a tailored modal expansion in the spanwise coordinate; however, only finitely many modes are cut-on, therefore the far-field noise can be quickly evaluated. The solution gives insight into the potential mechanisms behind the reduction of noise for plates with serrated trailing edges compared to those with straight edges. The two mechanisms behind the noise reduction are an increased destructive interference in the far field, and a redistribution of acoustic energy from low cut-on modes to higher cut-off modes. Five different test-case trailing-edge geometries are considered. The analytic solution identifies which geometries are most effective in different frequency ranges: geometries which promote destructive interference are best at low frequencies, whilst geometries which promote a redistribution of energy are better at high frequencies.