Acoustic and hydrodynamic analysis of the flow around an aerofoil with trailing-edge serrations
Acoustic and hydrodynamic analysis of the flow around an aerofoil with trailing-edge serrations
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DOI：
10.1017/jfm.2012.254
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发表时间：
2012-07
影响因子：
3.7
通讯作者：
L. E. Jones;R. Sandberg
中科院分区：
文献类型：
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作者：
L. E. Jones;R. Sandberg
摘要 对 NACA-0012 翼型周围的流动进行了直接数值模拟，采用浸入边界法来表示带锯齿和不带锯齿的平板后缘延伸部分。两种情况下后缘上对流的湍流边界层的特性相似。对于有锯齿的情况，观察到翼型上的流动产生的后缘噪声的幅度减小，并且发生噪声降低的频率间隔根据锯齿长度而不同。后缘噪声的方向性和展向相干性似乎基本上不受锯齿的影响。研究了后缘延伸部附近的流体动力学行为。可以在统计量中清楚地观察到由直后缘赋予湍流的流向不连续性，而对于锯齿状情况，没有观察到展向均匀不连续性。后缘锯齿似乎打破了对流到尾流中的较大湍流结构，并促进了源自锯齿本身的马蹄形涡流的发展。
Abstract Direct numerical simulations of the flow around a NACA-0012 aerofoil are conducted, employing an immersed boundary method to represent flat-plate trailing-edge extensions both with and without serrations. Properties of the turbulent boundary layer convecting over the trailing edge are similar for both cases. For cases with serrations, the trailing-edge noise produced by the flow over the aerofoil is observed to decrease in amplitude, and the frequency interval over which the noise reduction occurs differs depending on the serration length. The directivity and spanwise coherence of the trailing-edge noise appears largely unaffected by the serrations. The hydrodynamic behaviour in the vicinity of the trailing-edge extensions is investigated. The streamwise discontinuity imparted upon the turbulent flow by the straight trailing edge can clearly be observed in statistical quantities, whereas for the serrated case no spanwise homogeneous discontinuities are observed. The trailing-edge serrations appear to break up the larger turbulent structures convecting into the wake, and to promote the development of horseshoe vortices originating at the serrations themselves.