空氣動力學的研究中流體流動經過圓柱體是相當經典的題目之一，在高雷諾數下時，形成阻力驟降(drag crisis)現象此為臨界區間的特性，而阻力驟降的原因為分離泡形成於圓柱表面，而圓柱流場在臨界區域中極為複雜，尤其對於不同高寬比的有限高圓柱，因其受到自由端與基部流場影響使得整體的三維特性極強。
故本研究為探討高寬比(Aspect ratio, AR)為4、3、2時對非定常分離泡特性於雷諾數2×10^5至4×10^5間之影響，首先對高寬比(Aspect ratio, AR)3、4時之有限高圓柱進行油膜實驗，觀察臨界轉換區圓柱表面流場特性。
並對高寬比2至4之圓柱進行壓力量測實驗，透過使用間歇性因子分析其分離泡於各高寬比生成之間歇性，其中包含正負角度之非對稱分離泡及各高層間之同步性分離泡分析，最後以相關性分析其各高層間受分離泡生成之相關性，最後以歸納其高寬比2至4不同時高寬比影響其分離泡狀態的變化。

The investigation concentrates on the formation of unsteadiness of separation bubble around finite circular cylinder which is affected by different aspect ratios (AR) at transition critical regime. The experimental finite cylindrical models include a pressure experimental model (AR=2,3,4) and an oil-film experimental model (AR=3,4).
Through oil-film visualization observed that the flow characteristics of finite circular cylinder can be divided into three parts by different height positions. Namely, the free end at the upper level of the model, the middle level, and the lower level. In the critical regime, the alternating appearance of two separation line and separation bubble around the finite circular cylinder can be observed, and the frequency of alternation increases as the increase of Reynolds number, this means that the separation bubble is intermittent, and is clearly observed that the unsteadiness of separation bubble is affected by the aspect ratio as the aspect ratio decreases and the phenomenon occurs at lower Reynolds number.
In the study, the surface pressure of the finite circular cylinder was measured that was analyzed statistically. The unsteadiness of separation bubble was quantified by intermittency factor, this quantitative approach is used to demonstrate that the properties of unsteadiness of separation bubble: asymmetric, non-synchronous, and intermittent in flow characteristics due to the aspect ratio.

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