马赫数0.9喷气噪声的输入输出分析
Input-output analysis of Mach 0.9 jet noise
摘要：
利用输入输出分析方法研究了$M_j = 0.9$亚音速湍流射流雷诺平均Navier-Stokes解的小扰动放大行为。线性化Navier-Stokes（LNS）方程的预解式的奇异值分解（SVD）形成I/O模式对的正交规范集，按对应奇异值的大小降序排序。在这项研究中，我们设计了一个过滤器，以限制输入强迫是活跃的，只有在区域的湍流动能（TKE）的射流湍流。对于输出域，我们直接实现Ffowcs Williams-Hawkings（FWH）方法的I/O分析框架内测量沿圆弧分布的观察者的远场声音。通过这种方式，我们发现，由此产生的TKE加权输入模式捕获相干结构的近场湍流射流。最佳输入模式对应于在给定的强迫频率下由非对称伪高斯包络函数表示的波包。这些波包在$St > 0.5$的频率范围内保持类似的形状，并按比例缩放为$St^{-0.5}$。当最优模式是波包时，次优模式表示最优输入模式的退相干。通过将高保真大涡模拟（LES）数据投影到输入模式的基础上，我们发现输入模式确实捕获了射流中的声学相关动力学。的LES预测的远场声学恢复只使用几个数量的I/O模式。
英文摘要：
We examine amplifying behavior of small perturbations about Reynolds-averaged Navier-Stokes solutions (RANS) of a $M_j = 0.9$ subsonic turbulent jet using input-output (I/O) analysis. Singular value decomposition (SVD) of the resolvent of the linearized Navier-Stokes (LNS) equations forms an orthonormal set of I/O mode pairs, sorted in descending order by the magnitude of the corresponding singular values. In this study we design a filter to restrict input forcings to be active only in regions where turbulent kinetic energy (TKE) of jet turbulence is high. For an output domain, we directly implement the Ffowcs Williams-Hawkings (FWH) method within I/O analysis framework to measure far-field sound of observers distributed along an arc. In this way we find that the resulting TKE-weighted input modes captures coherent structures in the near-field of turbulent jets. Optimal input modes correspond to wavepackets represented by asymmetric pseudo-Gaussian envelope functions at a given forcing frequency. These wavepackets remain similar in shape over a range of frequencies for $St > 0.5$, and scale as $St^{-0.5}$. While the optimal mode is a wavepacket, sub-optimal modes represent decoherence of the optimal input mode. By projecting high-fidelity large eddy simulation (LES) data onto the basis of input modes, we find that input modes do indeed capture the acoustically relevant dynamics in the jet. The far-field acoustics predicted by the LES are recovered using only a few number of I/O modes.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
