本文以建立背向階梯流場完整的資料庫為主要目標，設定四組實驗條件包含兩種不同的突張比（ER=1.13與1.2）與兩種不同的入口自由流平均速度（U_∞=15 m/s與12 m/s），而寬高比均大於10（AR=15與10）以確保近似二維流場現象。藉由不同的入口自由流平均速度與階梯高度來改變初始進口條件之控制參數Reh。
本研究使用二維交叉探針（Dantec, 55P61）搭配熱線測速儀來量測背向階梯流場中的平均速度與紊流統計資訊，另外使用裂膜探針（Dantec, 55R55）來量測背向階梯後方之迴流區與再接觸區，並且建立完善的裂膜探針速度量測法及判斷法則，使其能正確獲得具有正逆速度之流場資訊，而本實驗中所有點的量測皆以數位訊號輸出，其中取樣頻率為10kHz，取樣時間為10秒。
本文中呈現了主流向、縱向的平均速度、紊流強度與紊流動能、雷諾應力以及主流向的偏態係數與峰態係數之紊流統計資訊，其演化過程均隨流場往下游發展先產生而後消散，皆符合紊流能量傳遞的瀑流原理；而利用偏態及峰態係數峰值所定義之邊界層厚度能較真實的描述流場的紊流行為，也比較符合流體現象上真實的物理意義。此外，以自相關係數與功率頻譜來分析流場之積分時間尺度、泰勒時間尺度都取得合理的結果，另外也驗證了慣性區域之能譜圖中能量與頻率呈現指數為-5/3之關係。

The purpose of this thesis is to build up the database of flow through a backward-facing step with four different inlet Reynolds numbers, Reh, which are changed by means of controlling the inlet mean velocity and the step height. The aspect ratio is set larger than 10（AR=15 and 10）in order to ensure quasi-2D motion of flow.
Measurements of mean flow and turbulence statistics in a backward-facing step flow field were taken using a cross-wire probe (55P61) in conjunction with a CTA system. A split-fiber film probe (55R55) was used to investigate reattaching and recirculation flows behind a backward-facing step. In all the experiments, the output signals were digitized and sampled for about 10 s at a frequency of 10 kHz for each measured points.
The streamwise and vertical profiles of mean velocity components turbulence intensities, kinetic energy, Reynolds stresses, skewness coefficient and kurtosis coefficient are presented reasonably and their evolution tendencies are consistent with what are described by the turbulent energy cascade theory. The boundary-layer thickness defined by the high-order correlations of skewness coefficient and kurtosis coefficient can describe the turbulent behaviors more faithfully as compared to the conventional one based on the mean velocity distribution. In addition, auto-correlation coefficients and power spectrum analyses are implement to investigate the Taylor time scale, integral time scale and the results make senses. The energy spectrum distribution showing the power law of -5/3 slope in the inertial subrange are also observed.

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