圆管内旋转点声源声学频域分析

Frequency Domain Solution of a Rotating Point Source in an Infinite Duct

在任意运动点声源声辐射频域解的基础上,利用无限长圆环管道的格林函数推导了旋转点声源在圆管内空间任一点处的声压计算公式,讨论了单极子点声源作旋转运动时的声场分布规律和声场方向性特征,研究了源频率、旋转频率和流动马赫数等对声场声学结构的影响.研究结果表明:声场分布具有很强的空间指向性;源频率和旋转频率的变化将伴随着多普勒效应出现;在点源的上、下游,各频率的声压幅值基本对称;来流马赫数的大小对声场有影响,会使某些频率的声辐射出现尖锐的峰值,因此要避免点声源在某些流动马赫数下旋转.

Frequency domain acoustic solution of moving sources and the Green function of an infinite duct are applied to deduce an acoustic formula for calculating the spatial sound pressure of a rotating point source in an infinite duct.The directionality characteristic and the distribution regularity of the sound field induced by a simple harmonic monopole rotating source are discussed,considering the influence of source frequency,rotating frequency and Mach number of the flow on the spatial sound pressure.The research conclusions indicate that the distribution of the sound field has intense directivity;the changes of source frequency and rotation frequency are accompanied by the emergence of Doppler effect;the sound pressures are symmetrical in both the upstream and downstream of the rotating source;and the rotating source should be avoided to rotate in the case that sound pressure might jump to a very higher magnitude under some flow Mach numbers.