On application of empirical mode decomposition for turbulence analysis in open-channel flows
On application of empirical mode decomposition for turbulence analysis in open-channel flows
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DOI：
10.1080/00221686.2023.2241838
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发表时间：
2023-09
影响因子：
2.3
通讯作者：
A. Zampiron;S. Cameron;V. Nikora
中科院分区：
文献类型：
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作者：
A. Zampiron;S. Cameron;V. Nikora
大尺度的拟序结构是明渠水流湍流的关键因素，其定量仍然难以捉摸。在这项工作中，我们使用经验模式分解(EMD)将速度时间序列分解成不同的模式，表示为“固有模式函数”(IMF)。速度自谱和共谱分析表明，大尺度(LSM)和超大尺度(VLSM)流体运动可以由特定的IMF组充分表示。EMD分析发现，LSM和VLSM之间的相关性产生了7%的雷诺剪应力。然而，对具有随机频谱相位的替代速度信号的EMD分析表明，所揭示的相关性实际上是EMD方法的伪影，不应被物理解释。
Large-scale coherent structures are key elements of open-channel flow turbulence, quantification of which remains elusive. In this work, we use empirical mode decomposition (EMD) to break down a velocity time series into different modes, denoted as “intrinsic mode functions” (IMFs). Analysis of velocity auto- and co-spectra indicates that large-scale (LSMs) and very large-scale (VLSMs) fluid motions are sufficiently represented by particular groups of IMFs. A correlation between LSMs and VLSMs, identified by the EMD analysis, was found to generate 7% of the Reynolds shear stresses. However, the EMD analysis of surrogate velocity signals with randomized spectral phases demonstrated that the revealed correlation is actually an artefact of the EMD approach and should not be interpreted physically.