【摘要】 应用Lighthill的气动声学理论对气流绕过圆柱产生气动噪声的机理进行实验研究,设计和建立了低噪声、低湍流度的模型风洞,其实验段截面为1OOmm×100mm,气流核心区的湍流度低于0.4%。对风啸声的气动声学理论进行了局部性的验证,并对相关测量技术进行了研究。实验表明,雷诺数在4×10~3～1×10~4的范围内,空间相关长度 l_c/d 在3.7左右,相关系数曲线下面积的重心矩γ/d为1.3,基本上保持不变。应用热线风速仪和 B ＆ K 声级计同时测量了圆柱绕流的流场和声场。从流速和声压的自功率谱以及它们的互功率谱研究表明,这三种方法确定的 Strouhal 数是一致的。雷诺数在6×10~3到1.8×10~4范围内,Strouhal 数为0.192。结果说明了圆柱的脱落旋涡和风啸声之间存在着内在的联系。更多还原

【Abstract】 Using Lighthill’s theory of aerodynamic sound,this paperpresents an experimental investigation of the mechanism of Aeoliantones generated by the flow around a circular cylinder.The low-noise,low-turbulence model wind tunnel was built for verificating the theoryof aerodynamic sound.The test section of this wind tunnel provides a100mm square open-jet with turbulence level below 0.4%,In theReynolds number range from 4×10~3 to 1×10~4 the spatial correlationlength l_c/d was about 3.7 and the moment of positive area under thecorrelation coefficient r/d was a constant of 1.3.The velocity of flow field and sound pressure level were simul-taneously measured by hotwire anemometer and B&K sound level meter.Strouhal numbers were also determined by means of three methods:power spectrum of velocity,power spectrum of sound pressure leveland cross-spectrum of them.The values were about the same,i.e.0.192,in the Reynolds number range from 6×10~3 to 1.8×10~4.These resultsshow the inherent connection between shed vortex and Aeolian tones.更多还原