本研究主要探討脈動式管流中之在過渡流時所發生的初始不穩定擾動現象，利用熱線測速儀(Hot wire)量測初始不穩定擾動發生時之流場速度剖面。使用Ensemble Empirical Mode Decomposition以及Empirical Mode Decomposition去除背景訊號截取出不穩定擾動分量，再將擾動分量搭配速度一次微分反曲點位置繪製成能譜圖，並利用Hilbert-Huang transform以及wavelet transform來計算不穩定擾動之特徵頻率，同時利用Rayleigh instability criterion 解釋初始不穩定擾動生成的所需條件以及Mixing layer 理論對初始不穩定擾動做出定性的分析，並整理歷屆資料嘗試找出各項實驗參數間與初始不穩定擾動之關係。利用上述分析方法及相關的理論和準則嘗試去解釋在過渡流時初始不穩定擾動發展的物理機制。

This study focused on initial instability disturbance phenomenon in the transition pulsating pipe flow. Using Hot-wire anemometer to measure the velocity profile when the unstable disturbance occurrence, then use Ensemble Empirical Mode Decomposition、Empirical Mode Decomposition and wavelet transform to analyzed the velocity signal, we found the disturbance region is effected by blockage ratio and Womersley number, also all the cases can satisfy Rayleigh instability criterion, but the value of non-dimensional frequency of mixing layer theorem only in the particular experiment situation can approach the value, so need to get more data to build the data base that can help us to do more discussion about the mechanism of initial unstable disturbances in pulsating pipe flow.

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