Coupled oscillations in the aeroacoustics of a Katana blade
Coupled oscillations in the aeroacoustics of a Katana blade
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武士刀叶片气动声学中的耦合振荡
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
M. Roger
中科院分区：
文献类型：
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作者：
M. Roger
本文通过实验研究了武士刀高速挥舞时气动声的音调特征。武士刀是日本武术中使用的剑的名称。它设计有锋利的切割边缘，厚的黑边，有时还有所谓的血槽。当通过空气处理时，刀片以不同的频率辐射声音。首先，由于叶片尾流中的von Karman涡脱落，可听到低频主声。第二个高频音是在有凹槽的武士刀的情况下产生的。这些音调是由沟槽上方的分离剪切层的自持振荡产生的，这些沟槽在掠流下表现得像空腔。在没有凹槽的武士刀的情况下，由于在边界层中生长的Tollmien-Schlichting波的声学反作用，可以听到其他高频音调。本文分析了不同攻角和相对流速下的声信号变化规律，着重分析了不同机理之间的耦合作用。将主要趋势与简单的自持振荡公式进行了比较。最后，可能使用的声音作为标准的不准确性处理的武士刀进行了讨论。
The paper investigates experimentally the tonal characteristics of the aerodynamic sound of a Katana blade handled at high speed. Katana is the name of the Japanese sword used in martial arts. It is designed with a sharp cutting edge, a thick black‐edge, and sometimes so‐called blood‐grooves. When handled through the air, the blade radiates sound at different frequencies. First a low‐frequency, dominant sound is heard due to the von Karman vortex shedding in the wake of the blade. Second high‐frequency tones are produced in the case of a Katana with grooves. The tones result from the self‐sustained oscillations of the detached shear layers over the grooves which behave like cavities under a grazing flow. In the case of a Katana with no groove, other high‐frequency tones are heard due to acoustic back‐reaction on the Tollmien‐Schlichting waves growing in the boundary layers. The variations of the acoustic signature with varying angle of attack and relative flow speed are analyzed in the paper, with emphasis on the coupling between the different mechanisms. The main trends are compared to simple self‐sustained oscillation formulae. Finally the possible use of the sound as a criterion of inaccuracies in the handling of the Katana is discussed.