體流經一鈍形體流場在流裡力學上是一個重要的研究課題，特別是有許多學者針對二維圓柱或方柱進行針對不同參數例如展旋比、渦流溢放特性、升阻力係數的變化及雷諾數效應等進行一系列研究與探討。近年來，因為在工程實務的需求上，許多學者針對三維的鈍形體流場結構及特性進行相關研究。
本研究利用流場可視化與風洞實驗中模型受力與熱線進行側向流場量測等實驗方式，針對流體流經有限高度之圓柱與方柱時，在頂部會有下沖流場結構與側向Karman型態渦流溢放之間相互影響因素進行探討。風洞實驗在內政部建築研究所歸仁建築風洞內進行，本研究風洞實驗所使用主要儀器有六力平衡儀、熱線探針、移動機構及資料擷取系統；有關視流實驗染液施放及PIV在成大流體系統感測實驗室內水槽進行，另一部份在內政部建研所的風洞內進行，包含有染液施放之視流實驗、PIV、表面油流實驗及煙流實驗。
本研究在風洞受力及流場量測之數據處理的方法上主要是採用西爾伯特-黃轉換法（HHT），將量測到橫風向與垂直向風力進行時間頻率域的轉換，並將所得HHT結果及設定頻率及振幅條件針對3D 柱體進行流場型態的分類，本研究主要將流體流經有限高度之柱體流場區分為幾種不同型態。
經由染液視流實驗結果可以發現，在有限高度方柱模型周圍流場可以觀察到不同的流場型態，且流場型態00的佔整個實驗實驗時間比例是最高，所代表意義為流場是相當三維之狀態。於油流實驗結果發現，在底部三維分離散效應所留下痕跡，於高雷諾數與高寬比高的方柱較明顯。高寬比為6方柱在PIV與煙流實驗結果可以觀察出，流體流經柱體頂部後，下沖氣流會有上下擺動現象，且向下流動時流向角度較高寬比為2模型大。
在風洞實驗結果經由分析後可以發現，將4種不同流場型態經由時間比重的統計，流場型態00在有限高的方柱將近60％，當模型為圓柱時，時間比重更高達70％。在實驗數據分析過程發現，其低頻分量的訊號佔有很高的能量，文中有針對此進一步探討後發現，這與4種不同流場型態中，00型態所佔相關性最高，且在高寬比為6方柱兩側利用熱線進行速度擾動量測，發現熱線與橫風向受力低頻分量的相關性為正相關，即為對稱的型態，但是在渦流溢放頻率域之分量則呈現反對稱的型態。

This study intends to investigate flow pass a finite cylinder with experiments carried out in a wind tunnel and a water channel. At first, the instantaneous data of lateral and vertical wind force on a finite cylinder was analyzed by the HHT method, and the each IMF component signal was decomposed. By a conditional sampling analyzing the aerodynamic forces experienced by a finite cylinder, four characteristic flow patterns can be categorized. These four flow patterns are named 00, 01, 10 and 11. The pattern 00 represents the flow pattern that neither the cross-wind vortex shedding nor the downwash motion is obvious; the pattern 10 represents the one that the vortex shedding is prominent but the downwash motion is not; the pattern 01 represents the pattern that the downwash motion is prominent but the vortex shedding is not; the pattern 11 implies the situation that both the vortex shedding and the downwash motion are prominent.
In the water channel experiments, the visualization results obtained by the dye injection technique clearly revealed the four flow patterns around a finite square cylinder.
In the wind tunnel experiments, the weighting distributions of the four flow patterns for the flow around a finite height square and circular cylinder indicated that the case 00 was the most popularly case. This flow pattern is mainly due to the low-frequency fluctuating motions around the finite cylinder model and the downwash motion over the free-end of the model. Moreover, it is found that this fluctuating motion is symmetric in the lateral direction mainly, which is notably different from the Karman-type vortex shedding anti-symmetric in the lateral direction

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