Flow Features and Self-Noise of Airfoils Near Stall or in Stall
Flow Features and Self-Noise of Airfoils Near Stall or in Stall
复制标题
近失速或失速翼型的流动特性及自噪声
DOI：
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
J. Christophe
中科院分区：
文献类型：
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作者：
S. Moreau;M. Roger;J. Christophe
对失速和失速附近翼型的流动特性和自噪声进行了详细的实验和数值研究。几种不同形状的翼型已在不同速度和不同迎角下进行了测试。失速噪声被证明可能有两种不同的状态，首先是轻微失速，然后是深度失速，具有明显的噪声特征。两者都出现在低频范围内并且具有偶极性质。然而，深失速具有超窄的峰值，这可能与剪切层不稳定性和大规模涡旋脱落有关。使用垂直喷嘴（大展弦比）和水平喷嘴（小展弦比）的实验也强调了安装对失速噪声特征的强烈影响。这两种设置根据弦长或分离气泡厚度产生不同的斯特劳哈尔数特征低频窄峰。在垂直设置中已经确定了与射流可能的相互作用。同时，在大展弦比设置中的长跨度 NACA0012 翼型上获得了 RANS 和 LES 结果。与射流的强相互作用已得到证实，并且实验壁压系数和特征斯特劳哈尔数都已匹配。还发现展向边界条件会强烈改变流场并模拟小纵横比和大纵横比的两种类型的实验。最后，针对失速噪声的低频范围特性开发了一个分析模型。它基于 Curle 对弦向声学上紧凑的偶极子的类比。如果使用实验壁压力谱和展向相干长度，它可以正确捕获实验光谱中看到的驼峰。
A detailed experimental and numerical investigation of the flow features and the self-noise of airfoils near stall and in stall has been achieved. Several airfoils of different shapes have been tested at different speeds and different angles-of-attack. The stall noise is shown to possibly have two different regimes, first a light stall and then a deep stall, with distinct noise features. Both are seen in the low frequency range and are of dipolar nature. Yet, the deep stall has extra narrow peaks which could be associated with shear layer instabilities and large scale vortex shedding. Experiments with a vertical nozzle (large aspect ratio) and a horizontal one (small aspect ratio) have also stressed the strong installation effects on the stall noise features. The two setups yield different low frequency narrow peaks for characteristic Strouhal numbers based either on the chord length or the separation bubble thickness. Possible interaction with the jet have been identified in the vertical setup. In parallel, both RANS and LES results have been obtained on the long-span NACA0012 airfoil in the large aspect ratio setup. The strong interaction with the jet has been confirmed and both the experimental wall pressure coefficient and the characteristic Strouhal numbers have been matched. The spanwise boundary conditions are also found to strongly modify the flow field and to mimic both types of experiments with small and large aspect ratios. Finally an analytical model has been developped for the low frequency range characteristics of the stall noise. It is based on Curle’s analogy for a dipole acoustically compact in the chordwise direction. It is shown to correctly capture the humps seen in the experimental spectrum provided the experimental wall pressure spectra and spanwise coherence lengths are used.
影响因子：
4.7
作者：
R. Sandberg;L. E. Jones;N. Sandham;P. Joseph
通讯作者：
R. Sandberg;L. E. Jones;N. Sandham;P. Joseph