Multimode radiation from an unflanged, semi-infinite circular duct
Multimode radiation from an unflanged, semi-infinite circular duct
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来自无凸缘、半无限圆形管道的多模辐射
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
C. Morfey
中科院分区：
文献类型：
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作者：
P. Joseph;C. Morfey
从一个单一的入射管道模式的声辐射的理论表达式，到达一个半无限的圆形无凸缘的管道与刚性壁的开口端，被用来获得数值结果（1）的单模声功率传输系数，和（2）的多模远场方向性因子。对于多模计算的模式被假定为非相干的，并采用加权模型，其中包括，作为特殊情况下，每个模式（以上截止），和激励均匀分布在管道横截面上的非相干单极子或轴向偶极子相等的功率。高频渐近特性的结果进行了详细的探讨，并给出了解析近似。研究结果对高大排气烟囱声功率测量具有实际应用价值。
Theoretical expressions for sound radiation from a single incident duct mode, arriving at the open end of a semi-infinite circular unflanged duct with rigid walls, are used to obtain numerical results for (1) the single-mode sound power transmission coefficient, and (2) the multimode far-field directivity factor. For the multimode calculations the modes are assumed incoherent, and a weighting model is adopted which includes, as special cases, equal power per mode (above cutoff), and excitation by incoherent monopoles or axial dipoles uniformly distributed over a duct cross section. High-frequency asymptotic features of the results are explored in detail and analytical approximations are given. The findings have practical application to sound power measurement from tall exhaust stacks.