Numerical analysis of aerodynamic noise mitigation via leading edge serrations for a rod–airfoil configuration
Numerical analysis of aerodynamic noise mitigation via leading edge serrations for a rod–airfoil configuration
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DOI：
10.1177/1475472x16672322
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发表时间：
2016-09
影响因子：
1
通讯作者：
B. Agrawal;Anupam Sharma
中科院分区：
文献类型：
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作者：
B. Agrawal;Anupam Sharma
使用不可压缩大涡模拟对串联布置的圆柱体（杆）和翼型之间的气动相互作用产生的噪声进行数值研究。杆的准周期性脱落以及由此产生的尾流撞击翼型，在两个几何形状上产生不稳定载荷。这些不稳定负载充当空气动力学声音的来源，并且声音以偶极子方向性辐射到远场。模拟时翼型设置为零攻角，基于棒直径的雷诺数为 Red = 48 K。与实验测量结果进行了比较：(a) 棒上的平均和均方根表面压力，(b) 棒尾流中的平均和均方根流向速度分布，(c) 近场速度谱，以及 (d) 远场压力谱。 Curle 的声学类比与模拟中的机翼表面压力数据一起用于预测远场声音。基于观察到的展向相干性的改进校正用于解释实验和模拟之间跨度长度的差异。近场空气动力学和远场声音预测与数据吻合良好。然后用具有锯齿状前缘几何形状的测试翼型替换直前缘翼型，同时保持平均弦长。这种新的配置也经过了数值分析，发现可以显着降低中高频范围的远场噪声频谱。源诊断表明，锯齿减少了翼型上的不稳定载荷，减少了沿翼展的相干性，并增加了翼展方向的相位变化，所有这些都有助于降噪。
Noise produced by aerodynamic interaction between a circular cylinder (rod) and an airfoil in a tandem arrangement is investigated numerically using incompressible large eddy simulations. Quasi-periodic shedding from the rod and the resulting wake impinges on the airfoil to produce unsteady loads on the two geometries. These unsteady loads act as sources of aerodynamic sound and the sound radiates to the far-field with a dipole directivity. The airfoil is set at zero angle of attack for the simulations and the Reynolds number based on the rod diameter is Red = 48 K. Comparisons with experimental measurements are made for (a) mean and root mean square surface pressure on the rod, (b) profiles of mean and root mean square streamwise velocity in the rod wake, (c) velocity spectra in the near field, and (d) far-field pressure spectra. Curle’s acoustic analogy is used with the airfoil surface pressure data from the simulations to predict the far-field sound. An improved correction based on observed spanwise coherence is used to account for the difference in span lengths between the experiments and the simulations. Good agreement with data is observed for the near-field aerodynamics and the far-field sound predictions. The straight leading edge airfoil is then replaced with a test airfoil with a serrated leading edge geometry while maintaining the mean chord. This new configuration is also analyzed numerically and found to give a substantial reduction in the far-field noise spectra in the mid- to high-frequency range. Source diagnostics show that the serrations reduce unsteady loading on the airfoil, reduce coherence along the span, and increase spanwise phase variation, all of which contribute to noise reduction.