Acoustic sources in a turbulent jet: A direct numerical simulation study
Acoustic sources in a turbulent jet: A direct numerical simulation study
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湍流射流中的声源：直接数值模拟研究
DOI：
10.2514/6.1999-1858
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发表时间：
1999
期刊：
影响因子：
--
通讯作者：
J. Freund
中科院分区：
文献类型：
--
作者：
J. Freund
对马赫数0.9、雷诺数3600的射流进行了直接数值模拟和分析。模拟结果与Stromberg等人进行的相应实验结果非常吻合。为了了解噪声机制，莱特希尔的理论被用来定义一个标称声源，使用傅立叶方法计算，以提供其流向波数和频率组成。它示出的辐射部分的源，定义其组件与超声速相速度的总和，具有显着不同的字符比完整的莱特希尔源。同样，湍流动能被证明是不良相关的辐射源。在0.1~ 0.5a之间，声源的流向相速度分布比较均匀，其中aoo为环境声速。辐射源的“结构”是通过过滤其非辐射成分来检查的。这揭示了一个简单的调制谐波的形式，可以预测的线性不稳定性分析。一个简单的模型被用来证明，噪音是非常敏感的这种形式的轻微中断。
A direct numerical simulation of a Mach 0.9, Reynolds number 3600 jet is presented and analyzed. The simulation results are shown to be in excellent agreement with corresponding experiments conducted by Stromberg et al.’ To understand noise mechanisms, Lighthill’s theory is used to define a nominal acoustic source which is computed using Fourier methods to provide its streamwise wavenumber and frequency makeup. It is shown that the radiating portion of the source, defined by the sum of its components with supersonic phase velocities, has a significantly different character than the full Lighthill source. Similarly, the turbulent kinetic energy is shown to be poorly correlated with the radiating source. Streamwise phase velocities of the source are found to be distributed fairly evenly between 0.1~~~ and 0.5a,, where aoo is the ambient speed of sound. The “structure” of the radiating source is examined by filtering its nonradiating components. This reveals a simple modulated harmonic wave form as might be predicted by linear instability analysis. A simple model is used to demonstrate that the noise is extremely sensitive to minor disruptions of this form.