论文标题
尖叫喷气机的波浪
Waves in screeching jets
论文作者
论文摘要
通过实验测量和线性稳定性理论，考虑了尖叫喷气机中各种波浪结构之间的相互作用。尖叫喷气机的速度快照用于通过正确的正交分解产生尖叫周期的降序模型。然后，将流向傅立叶滤波施加以隔离阴性和正向波数的成分，这对于该射流中的感兴趣波浪对应于上游和下游旅行波。对实验得出的基本流进行了全球稳定性分析，证明与通过实验获得的结果非常匹配，表明此处考虑的机制在线性框架中很好地表示。在这两个分析中，三种不同的波浪结构都是明显的。这三个波是Tam＆Hu（1989）首先显示的圆柱形涡流板支持的波。一个是开尔文 - 霍尔姆尔兹模式。另一个是上游旅行导游的喷气模式，它一直是最近讨论的话题。以前尚未在尖叫的喷气机中鉴定出具有正相速度的第三个成分。我们提供的证据表明，这种下游旅行波是一种类似管道的模式，类似于Towne等人在高苏氏射流中发现的模式。 （2017）。我们进一步证明，根据Tam＆Tanna（1982）首先提出的理论，Kelvin-Helmholtz Wavepacket与流动中的冲击细胞之间的相互作用产生了后两个波。最后，我们考虑了在尖叫喷气机中明显的相干速度波动的周期性空间调节，并表明该调节是三个小波般的结构叠加的结果，没有证据表明流动中的冲击调节了Kelvin-Helmholtz波袋的生长。
The interaction between various wavelike structures in screeching jets is considered via both experimental measurements and linear stability theory. Velocity snapshots of screeching jets are used to produce a reduced order model of the screech cycle via proper orthogonal decomposition. Streamwise Fourier filtering is then applied to isolate the negative and positive wavenumber components, which for the waves of interest in this jet correspond to upstream and downstream-travelling waves. A global stability analysis on an experimentally derived base flow is conducted, demonstrating a close match to the results obtained via experiment, indicating that the mechanisms considered here are well represented in a linear framework. In both analyses, three distinct wavelike structures are evident. These three waves are those first shown by Tam & Hu (1989) to be supported by a cylindrical vortex sheet. One is the Kelvin-Helmholtz mode. Another is the upstream-travelling guided jet mode that has been a topic of recent discussion. The third component, with positive phase velocity, has not previously been identified in screeching jets. We provide evidence that this downstream-travelling wave is a duct-like mode similar to that recently identified in high-subsonic jets by Towne et al. (2017). We further demonstrate that both of the latter two waves are generated by the interaction between the Kelvin-Helmholtz wavepacket and the shock cells in the flow, according to a theory first proposed in Tam & Tanna (1982). Finally, we consider the periodic spatial modulation of the coherent velocity fluctuation evident in screeching jets, and show that this modulation is the result of the superposition of the three wavelike structures, with no evidence that the shocks in the flow modulate the growth of the Kelvin-Helmholtz wavepacket.
