Spectral broadening by shear layers of open jet wind tunnels
Spectral broadening by shear layers of open jet wind tunnels
复制标题
开放式喷射风洞剪切层的光谱展宽
DOI：
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
C. Spehr
中科院分区：
文献类型：
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作者：
P. Sijtsma;S. Oerlemans;Tim G. Tibbe;T. Berkefeld;C. Spehr
开放射流风洞中剪切层的存在使航空声学测量变得复杂。来自风洞模型的音调在通过湍流剪切层流传播时受到频谱展宽（或“干堆”）的影响。例如，在对旋转螺旋桨的测量中，这模糊了转子音调的识别和量化。本文对开放射流风洞剪切层的谱展宽进行了理论和实验研究。推导了一个简单的物理模型，该模型预测了展宽量作为单个参数的函数，该参数与风速、源频率和切变层厚度成正比。该理论与五个不同风洞的实验数据进行了比较。特别是对于较小的风洞，理论和实验之间的一致性通常很好，这使得从拓宽的频谱中检索音调的原始电平成为可能。
The presence of shear layers in open jet wind tunnels complicates aeroacoustic measurements. Tones from wind tunnel models are subject to spectral broadening (or ‘haystacking’) when propagating through the turbulent shear layer flow. For example, in measurements on contra-rotating propellers this obscures the identification and quantification of rotor tones. This paper describes a theoretical and experimental study into spectral broadening by the shear layers of open jet wind tunnels. A simple physical model is derived which predicts the amount of broadening as a function of a single parameter, which is proportional to wind speed, source frequency and shear layer thickness. The theory is compared against experimental data from five different wind tunnels. Especially for the smaller wind tunnels the agreement between theory and experiment is generally good, which makes it possible to retrieve the original level of a tone from a broadened spectrum.