包含平均旋流的圆环管道声传播的模态分析

Normal mode analysis for the sound propagation in a lined annular duct with mean swirling flow

通过对三维线化欧拉方程的特征模态分析,研究包含平均旋流情况下声波在敷设声衬的圆环管道中的传播.特征模态分析采用谱配置方法计算轴向波数谱及扰动量的分布.当有平均旋流存在时,特征模态谱主要包括近/纯声模态和近/纯对流模态,旋流的存在甚至会改变传播模态个数,从而改变声波传播截止特性.在验证程序正确性的基础上,研究流动参数及声衬对声模态及对流模态的影响.

Sound propagation in a lined annular duct with mean swirling flow was investigated via the normal mode analysis of three-dimensional （3-D） I.inearized Euler equations, and was calculated as a generalized eigenvalue problem by a spectral collocation technique. Axial eigenmodes spectrum which are mainly composed of nearly/purely acoustic modes and nearly/purely convected modes with mean swirl and relative unsteady disturbances can then be determined. Mean swirl may even change the number of the propagating acoustic modes, and consequently affect the cut on/cut-off characteristics of sound propagation. After valida tion of the approach, the effects of flow parameters and liner on the acoustic modes and con vected modes are discussed.