本研究旨在探討脈動式管流中之初始不穩定擾動現象，藉由馬達驅動管流下游之檔板 (稱流場控制器) 旋轉，造成管流流速隨時間呈脈動式變化，此脈動式非定常管流場之三項實驗參數分別為Womersley number、平均雷諾數與振幅雷諾數。實驗中利用Hot-wire量測瞬時流速，並搭配熱膜感測器貼於壁面沿著展向方向 ，再依據流場控制器的光電輸出信號做流速相位平均(phase average)；在二維擾動的假設下，比較不同相位的流速分佈曲線，吾人可探討不穩定擾動在一個脈動週期之內的變化趨勢，並使用經驗模態分離法將擾動訊號自原始訊號中分離出來，做進一步定量分析。實驗結果發現初始擾動發生在管流分佈呈減速之區域，且管流徑向分佈曲線具反曲點，這些實驗觀察可運用Rayleigh instability的觀點予以解釋。

An experimental investigation was conducted in the developing region of a pulsating pipe flow, which was produced by a circular disk in rotation at the downstream end of the pipe flow. The flow can be characterized by three experimental parameters, namely, the Reynolds number based on the time-mean velocity, the Reynolds number based on the pulsating velocity amplitude and the Womersley Number representing the non-dimensional frequency of the pulsating flow. In the experiment, the velocity measurements were made by a boundary type hot-wire. The spanwise characteristics of unstable disturbances were observed by MEMS thermal-film sensors flushed with the wall across 40 degrees in the azimuthal direction. Then, referred to the photoelectric output of the flow controller, the velocity signals were phase-averaged. Moreover, in the assumption of two-dimensional perturbations, the Empirical Mode Decomposition Method was employed to extract the disturbance component from the phase-averaged velocity traces. Therefore, the characteristics of the disturbance were examined in detail. The results obtained indicate that the unstable disturbances are developed when the flow near the wall is in deceleration, and are occurred at the radial positions where the inflection points take place. This finding can be further explained from the viewpoint of Rayleigh instability.

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