Experimental Evaluation of Theories for Trailing Edge and Incidence Fluctuation Noise
Experimental Evaluation of Theories for Trailing Edge and Incidence Fluctuation Noise
复制标题
后缘和入射脉动噪声理论的实验评估
作者：
M. Fink
进行了试验以评价后缘噪声和迎角波动噪声的相互矛盾的理论。在消声风洞中，以31.5-177 m/sec（108-580 fps）的速度和标称4 °和6° 7 °网格产生的湍流水平，对带有齐平安装的表面压力传感器的平板翼型进行了试验。在一系列试验中，翼型流线型地进入风洞喷管，并延伸到喷管唇口之外，用于研究没有前缘和只有一侧流动的后缘噪声。正如Ffowcs威廉姆斯和霍尔以及蔡斯所预测的那样，发现这种噪声随速度的五次方和湍流级的平方而变化。在高频功率谱密度衰减与频率的10/3功率近似成反比，由大通预测。Hayden的相关性对数据的预测很差。附加的试验是将翼型安装在风洞中心线上进行的，两侧气流和湍流对流通过前缘。由入射波动引起的表面压力谱在高频下由Filamentum和Mugridge理论合理地预测，但在低频下由Filamentum理论更接近地预测。当Strouhal数和马赫数的乘积大于0.5时，远场谱的衰减比他们的理论在紧凑源分析中预测的要快。海登对声学非紧性的修正，也可能描述了升力的相位抵消效应，使费迪南的理论与远场谱一致。
Tests were conducted to evaluate conflicting theories for trailing edge noise and for incidence fluctuation noise. A flat-plate airfoil with flush-mounted surface pressure transducers was tested in an anechoic wind tunnel at velocities of 31.5-177 m/sec (108-580 fps) and nominal 4 and 6°7o grid-generated turbulence levels. In one series of runs, the airfoil was faired into the tunnel nozzle and extended beyond the nozzle lip for studies of trailing edge noise without a leading edge and with flow on only one side. Such noise was found to vary with velocity to the fifth power and turbulence level squared, as predicted by Ffowcs Williams and Hall and by Chase. Power spectral density at high frequencies decayed approximately inversely with frequency to the 10/3 power, as predicted by Chase. The data were poorly predicted by Hayden's correlation. Additional tests were conducted with the airfoil mounted on the tunnel centerline, with flow on both sides and turbulence convected past the leading edge. Surface pressure spectra caused by incidence fluctuations were reasonably predicted by the theories of Filotas and Mugridge at high frequencies, but were more closely predicted by that of Filotas at low frequencies. Far-field spectra decayed more rapidly than was predicted by their theory within a compact source analysis when the product of Strouhal number and Mach number was larger than about 0.5. Hayden's correction for acoustic noncompactness, which may also describe a phase cancellation effect on lift force, brought Filotas' theory into agreement with far-field spectra.