本研究目的在於以長時間的實驗數據統計方式探討流體流經一矩形截面凸狀物回覆再接觸現象。將模型置於距風洞入口端後方10H處，實驗於ReH為3.02×104，凸狀物寬高比為4，使用熱絲觀念(Thermal Tuft)的量測方式，以統計方法找出長時間120秒之擾動差分值(Deviations Value)，其值為正規化溫度後反相位訊號的時間點，在此時間點擾動差分值皆為負值，且為回覆再接觸點於發生的時間點縮短往上游移動的表徵，透過這些時間點與熱線測速儀的訊號交互相關性分析(Cross Correlation)，以數據統計結果探討回覆再接觸擺盪現象的所造成渦流拉伸潰散，於矩形凸狀物流場中三維非定常現象的影響。
實驗結果發現回覆再接觸區發生在距凸狀物前緣3.2H~3.4H之間，以溫度感測器經由訊號百分比分析，得回覆再接觸點(Reattachment Point)在3.32H處。且長時間對溫度感測器正規化溫度後反相位訊號的統計結果可發現流體受分離剪流層影響而造成物體表面上壁迴流區隨著流量的不平衡，膨脹縮小造成回覆再接觸區有一個低頻非周期來回擺盪行為，一秒內的擺盪次數約為14.2次，其無因次化頻率St為0.05。而藉由相關性分析可得於接近壁面Y=0.2處，在低頻擺盪發生時，短時間渦流的速度分佈情形顯示溫度感測器與熱線測速儀在同一手指結構中，其手指結構大小約為1H。當分離剪流層曲率增加回覆再接觸點往前移動的瞬間，流場的三維效應相當的明顯，而反相位訊號發生時，熱線測速儀在X-Y及X-Z方向所量測到U速度之相關性係數的結果不相同，且於迴流區中U、V、W動量傳遞增加，由此可知流場呈現出三維非定常結構。

This study is intended using the long time experiment data to investigate the three-dimensional, unsteady behavior of flow reattachment over a surface-mounted rectangular block. The model was located behind the wind tunnel flow inlet at10H and the ratio of width versus height of the block is equal 4 for the Reynolds number at 3.02×104. The experiment was carried out using the self-made MEMS thermal films sensor and thermal tuft method to measure the span-wise direction on the surface-mounted find out the long time deviations value at Y=0.2H, the out-phase signal after the normalized temperature value, whose the instantaneous flapping motion at the reattachment zone. The purpose of this study is to quantify the characteristics of the three-dimensional unsteady the instantaneous flapping motion and the vortex structure of a simple rectangular block at the reattachment zone by mean of cross correlation analysis.
It is found that the reattachment length is 3.2H~3.4H and the reattachment point is 3.32H by the signal percentage analysis. To statistics the long time deviations value of the temperature sensor signal, there was a low-frequency aperiodicity instantaneous flapping motion of the reattachment zone because of the inversed pressure gradient effect on the separate shear layer, the mean of frequency about 14.2 by a second and the Strouhal number, St, is 0.05. Cross correlation analysis of the signal between the deviations value of the temperature sensor and the ×-type hot-wire signal, it has been found that the characteristic span-wise lengths of the three-dimensional flow structures about 1H. And further noted that the unsteady behaviors of the reattachment out-phase signal occurred, the instantaneous velocity distribution X-Y and X-Z of the hot-wire signal show a different trend, which are considering the strong momentum transfer at the recirculation zone.

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