本研究主要探討脈動式管流中之初始不穩定擾動現象，利用熱線測速儀量測流場之速度，並搭配實驗室製作之熱膜感測器沿著展向方向黏貼，橫跨 40° 的範圍。並利用Hilbert-Huang transform來計算不穩定擾動之特徵頻率。此外，利用熱膜感測器觀察其展向特性，利用Ensemble Empirical Mode Decomposition去除背景訊號截取出不穩定擾動之分量，配合交叉相關性分析，可以清楚分辨出不穩定擾動之二維與三維特性。同時量測MEMS sensor與hot-wire的訊號，並且移動hot-wire的徑向位置，利用上述分析方法可以讓吾人更加了解初始擾動發展的物理機制。

An experimental investigation of the unstable disturbances in the developing region of pulsating pipe flow was conducted, relevant to the onset of the laminar-turbulent transition process. The velocity measurements were made by a boundary type hot-wire. The spanwise characteristics of unstable disturbances were observed by five self-made MEMS thermal-film sensors flushed with the wall across 40 degrees in the azimuthal direction. The characteristic frequency of the unstable disturbances in each cycle was resolved by the Hilbert-Huang transformation. Furthermore, the unstable disturbances measured by the MEMS sensors were analyzed with the Ensemble Empirical Mode Decomposition method to remove the trend signal. Subsequently, the cross-correlation analysis revealed the distinction between the two-dimensional and the three-dimensional unstable disturbances clearly. Simultaneous measurements using a hot-wire traversed along the radial direction. Based on the MEMS sensors on the wall, a postulation is given concerning the initial unstable disturbance developed in the periodical pipe flow.

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