本研究以實驗方式探討圓柱表面流場在雷諾數為1.73×10^5~5.86×10^5間的空氣動力特性。實驗首先量測臨界區中，基部壓力隨雷諾數之變化情形，再利用圓柱左右兩側±900位置的擾動壓力係數來判斷圓柱流場進入單分離泡區的最低雷諾數，如此一來，即定義出圓柱流場在預臨界區、單分離泡區及雙分離泡區中，雷諾數分布的範圍。
　　在瞭解各子區域的雷諾數範圍後，選定四組雷諾數以量測各個子區域內圓柱表面的壓力分布情形，再藉由油流實驗進行視流觀察，並與實驗量測之結果相互比對，成功地找出流動分離及再回覆現象發生的位置，並利用量測所得的壓力分布，以積分方法計算出圓柱在臨界區中的升、阻力係數。
　　至於瞬時頻率的分析，藉由小波轉換進行數據處理，吾人得以在預臨界區中層流分離發生的位置，解析出壓力訊號中夾帶的瞬時溢放頻率，此分析方法貢獻了快速富立葉轉換無法提供的瞬時資訊；而在單分離泡形成之初，圓柱表面的溢放訊號呈不連續分布且劇烈振盪，此乃溢放行為與分離泡之形成產生交互作用所致，分離泡發生前後，流場中會出現兩溢放主頻。
　　最後，亦可藉此實驗研究之結果對風洞進行性能驗證，以進一步證實風洞的流場品質符合原先設計之要求。

　In this study, we investigated the aerodynamic characteristics of the flows around circular cylinders at Reynolds numbers 1.73×10^5~5.86×10^5. First of all, the base pressures across the critical regime were measured, therefore the relation between base-pressure coefficient and Reynolds number was reduced. Then, we determined the lowest Reynolds number at which the flow field entered the one-bubble regime by comparing the root-mean-square values of the pressure coefficients on two sides of a cylinder. In this way, all the sub-regimes in the critical regime were classified.
　After the ranges of Reynolds number in each of the sub-regimes had been confirmed, the pressure distributions around circular cylinders at four specific Reynolds numbers were measured. By comparing the results of oil-flow visualization with the pressure measurements, the positions where laminar/turbulent separation and reattachment took place were successfully identified. Subsequently, the lift and drag coefficients by integrating the pressure distributions on the surface of circular cylinders were made.
　We analyzed the instantaneous behavior of vortex shedding by processing the measured data with wavelet transformation. This method offers instantaneous information that fast Fourier transformation can not provide. At the Reynolds number near lower end of one bubble regime, the unsteadiness of a bubble causes the instantaneous frequency of vortex shedding to vary discontinuously and fluctuate violently.
　At last, by comparing the above results with references, the flow quality of the ABRI wind tunnel was verified.

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