Study on Large-Scale Amplitude Modulation of Near-Wall Small-Scale Structures in Turbulent Wall-Bounded Flows
Study on Large-Scale Amplitude Modulation of Near-Wall Small-Scale Structures in Turbulent Wall-Bounded Flows
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DOI：
10.1007/978-3-030-79561-0_7
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发表时间：
2020-11
期刊：
影响因子：
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通讯作者：
E. Mäteling;M. Klaas;W. Schröder
中科院分区：
文献类型：
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作者：
E. Mäteling;M. Klaas;W. Schröder
最近，Mäteling等人提出了一种新的方法来研究湍流壁面边界流中的内外相互作用。[8]，它解决了叠加、突发事件和基于随时间变化的流向速度波动的幅度调制的综合影响。在目前的研究中，这种方法被扩展到所有三个速度波动分量。由于加入了壁法向速度起伏，因此可以更详细地研究爆发事件，而不受叠加的影响。通过使用多变量经验模式分解进行尺度分离，可以同时分解两个壁法向位置的所有速度分量，以确保所得到的模态表示之间的尺度对齐。结果表明，三种速度分量都存在叠加效应和调幅效应，但流向脉动的叠加效应和调幅作用最强。通过传统的互相关法也可以检测到扫掠和抛射的高度一致性。
Recently, a novel approach to study the inner-outer interactions in turbulent wall-bounded flows has been presented by Mäteling et al. [8], which tackles the combined effects of superposition, bursting events, and amplitude modulation based on the time-dependent streamwise velocity fluctuations. This approach is extended in the current study to all three velocity fluctuation components. Due to the incorporation of the wall-normal velocity fluctuations, the bursting events can be study in more detail and independently of the superposition. By using a multivariate empirical mode decomposition for the scale separation, all velocity components at both wall-normal positions can be decomposed simultaneously to ensure proper scale alignment between the resulting modal representations. The results show that the superposition effect and the amplitude modulation exist in all three velocity components but are most intense for the streamwise fluctuations. A high level of coherence of the sweeps and ejections is also detected by conventional cross-correlation.