Numerical analysis on flue instruments based on aerodynamic sound theory

在Howe能量推论的基础上，研究了小型烟道仪表模型中流体场和声场之间的相互作用，从而可以估计声场和流体场之间的能量传递。我们发展了一种数值方法来实现Howe能量推论的计算。结果，我们找出了嘴开口附近的哪个区域对声音的产生起主要作用：气动声音是由振荡射流产生的，而不是边缘的涡流产生的。我们的结果与Yoshikawa等人以前的实验结果基本相同。为Howe的理论预测提供了数值证据。我们进一步用不可压缩近似和全可压缩计算计算了Lighthill声源。我们发现这两种计算之间存在质的和量的差异。这表明通常使用的不可压缩近似是不够的。

We study the interaction between the fluid field and the acoustic field in a small flue-instrument model based on Howe's energy corollary theory, which allows us to estimate the energy transfer from the acoustic field to the fluid field and vice versa. We develop a numerical method to implement the calculation of Howe's energy corollary. As a result, we find out which area near the mouth opening mainly contributes to the generation of sound: the aerodynamic sound is generated from the oscillating jet rather than vortices shed at the edge. Our result is essentially the same as the previous experimental result by Yoshikawa et al. and provides a numerical evidence to Howe's theoretical prediction. We further calculate Lighthill's sound source with the incompressible approximation and with full-compressible calculation. We find qualitative and quantitative differences between the two calculations. It indicates that the incompressible approximation usually used is insufficient.