A study of Mach wave radiation using active control
A study of Mach wave radiation using active control
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基于主动控制的马赫波辐射研究
DOI：
10.1017/jfm.2011.196
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发表时间：
2011
影响因子：
3.7
通讯作者：
M. Samimy
中科院分区：
文献类型：
--
作者：
M. Kearney;Jin;M. Samimy
马赫波辐射是人们更了解的喷气噪声源之一。然而，其发生的确切条件很难确定，迄今为止的文献通常探讨远高于其发生条件的马赫波辐射。为了确定马赫波辐射发生的条件并探索其在发生期间及之后的行为，使用了马赫数 Mj = 0.9、1.3 和 1.65 以及停滞温度比范围为 To/T∞ = 1.0–2.5（声学马赫数 0.83–2.10）的三种理想膨胀射流。使用远场麦克风阵列、纹影成像和流向二分量粒子图像测速来收集数据。使用电弧灯丝等离子体致动器强制喷射，为马赫波辐射的详细检查提供了前所未有的工具。探讨了射流对各种强迫参数（一种方位模式 m = 0、1 和 3 和一种斯特劳哈尔数 StDF = 0.09–3.0 的组合）的响应。相位平均纹影图像清楚地显示了马赫波辐射响应喷射操作条件和强迫参数变化的发生和演变。据观察，马赫波辐射是由紧邻大型结构的近场流体动压力波动的合并引发的。随着射流出口速度的增加，流体动力压力波动合并，首先形成弯曲的波前，然后平坦化为通常与马赫波辐射相关的圆锥形波前。结果表明，最大和最相干的结构（例如 m = 0 和 StDF ~ 0.3 的强迫）会产生最强的马赫波辐射。相反，当结构相干性最差时（例如，m = 3 且 StDF > 1.5 时的强迫），马赫波辐射最弱。
Mach wave radiation is one of the better understood sources of jet noise. However, the exact conditions of its onset are difficult to determine and the literature to date typically explores Mach wave radiation well above its onset conditions. In order to determine the conditions for the onset of Mach wave radiation and to explore its behaviour during onset and beyond, three ideally expanded jets with Mach numbers Mj = 0.9, 1.3 and 1.65 and stagnation temperature ratios ranging over To/T∞ = 1.0–2.5 (acoustic Mach number 0.83–2.10) were used. Data are collected using a far-field microphone array, schlieren imaging and streamwise two-component particle image velocimetry. Using arc filament plasma actuators to force the jet provides an unprecedented tool for detailed examination of Mach wave radiation. The response of the jet to various forcing parameters (combinations of one azimuthal mode m = 0, 1 and 3 and one Strouhal number StDF = 0.09–3.0) is explored. Phase-averaged schlieren images clearly show the onset and evolution of Mach wave radiation in response to both changes in the jet operating conditions and forcing parameters. It is observed that Mach wave radiation is initiated as a coalescing of the near-field hydrodynamic pressure fluctuations in the immediate vicinity of the large-scale structures. As the jet exit velocity increases, the hydrodynamic pressure fluctuations coalesce, first into a curved wavefront, then flatten into the conical wavefronts commonly associated with Mach wave radiation. The results show that the largest and most coherent structures (e.g. forcing with m = 0 and StDF ~ 0.3) produce the strongest Mach wave radiation. Conversely, Mach wave radiation is weakest when the structures are the least coherent (e.g. forcing with m = 3 and StDF > 1.5).