Time-Accurate Simulations and Acoustic Analysis of Slat Free Shear Layer
Time-Accurate Simulations and Acoustic Analysis of Slat Free Shear Layer
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DOI：
10.2514/2.1817
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发表时间：
2002
期刊：
影响因子：
2.5
通讯作者：
M. Khorrami;B. Singer;M. Berkman
中科院分区：
文献类型：
--
作者：
M. Khorrami;B. Singer;M. Berkman
对多单元高升力布局进行了非定常计算模拟。重点研究了板湾地区自由剪切层的精确时空分辨率。在以前的模拟中，湍流模式的过度耗散效应是如此普遍，通过关闭板条湾区域的湍流产生项来绕过。详细解释了采取这一步骤的理由和物理论据。这种多余的阻尼力的去除使得剪切层能够放大大型结构，达到适当的非线性饱和状态，并允许涡流合并。大尺度扰动是自激的，与我们以前的完全湍流模拟不同，不需要剪切层的外部强迫。为了得到Ffowcs Williams和Hawking方程的声场分布，利用模拟的时间精度流动数据对Ffowcs Williams和Hawking方程进行了数值计算。目前计算的远场声谱与测量的远场声谱的比较表明，与过去的计算相比，幅度和频率成分的一致性要好得多。模拟了迎角对板条辐射声场流动特性的影响。
Unsteady computational simulations of a multi-element, high-lift configuration are performed. Emphasis is placed on accurate spatiotemporal resolution of the free shear layer in the slat-cove region. The excessive dissipative effects of the turbulence model, so prevalent in previous simulations, are circumvented by switching off the turbulence-production term in the slat cove region. The justifications and physical arguments for taking such a step are explained in detail. The removal of this excess damping allows the shear layer to amplify large-scale structures, to achieve a proper non-linear saturation state, and to permit vortex merging. The large-scale disturbances are self-excited, and unlike our prior fully turbulent simulations, no external forcing of the shear layer is required. To obtain the farfield acoustics, the Ffowcs Williams and Hawkings equation is evaluated numerically using the simulated time-accurate flow data. The present comparison between the computed and measured farfield acoustic spectra shows much better agreement for the amplitude and frequency content than past calculations. The effect of the angle-of-attack on the slat's flow features radiated acoustic field are also simulated presented.