臺灣博碩士論文加值系統

　　河川中非透水性結構物依據其設計目的，可能提供阻擋水流、保護後方構造物及減緩沖刷之功效，透水性結構物不僅保有前述各項功用，並且還增加了生態保護的功能。橫跨河川構築之透水結構物，其孔隙構造能夠讓水中生物進行縱向遷徙，也能夠讓微生物附著來分解水中的有機質，進而達到河川淨化以及增加水中溶氧等作用，因此為了解其附近及內部流場特性，乃環境水力學中之重要課題。本研究選用三種不同的孔隙率來做實驗，其中兩個為透水結構物（孔隙率分別為34.9%及43.3%）而另一個為不透水結構物(孔隙率0%)，主要來比較其流場在完全浸沒一型之水流型式（圖1-1A）時之變化，利用音波都普勒流速儀（簡稱ADV）量測結構物附近之流場，而透水結構物內部之流場則採用電磁式流速儀進行量測。
　　本研究之試驗結果顯示，在透水結構物及流體交界面間，因為孔隙性的關係在交界面產生邊界滑動速度，因此在透水結構物上方交界面處之流速大於不透水結構物；紊流強度、紊流動能、雷諾剪應力及渦度方面，可以發現到其最大值都是出現在結構物的周圍及其後端，且隨著距離減小，三者之強度皆與孔隙率成反比，隨孔隙率增大而減小；整體觀察發現透水結構物有降低紊流強度、紊流動能、雷諾剪應力及渦度等作用；在本研究之實驗條件下，發現回流區與孔隙率成正比，孔隙率為0%的不透水結構物，其回流長度在範圍約為6.6~8.5倍結構物高，孔隙率為34.9%的結構物約為9.0~10.8倍結構物高，而孔隙率為43.3%的結構物約為10.2~11.2倍結構物高，造成此現象主要是因為透水結構物會有穿越流（Bleed flow）流出，造成回流長度增加；在結構物內流量可觀察到，孔隙率愈大內部流量愈多，且受到的阻力影響，透水結構物內部流量隨著斷面距離增加而遞減。

　　The characteristics of turbulent flow over permeable and non-permeable structures are studied experimentally. The permeable structures are modeled by two glass beads of diameters equal to 2.5cm and 1.5cm, resulting in geometric porosities (ε) were equal to 43.3% and 34.9%, respectively. The flows over the structures are measured by the acoustic Doppler velocimeter (ADV) and the flows within the permeable structures are measured by the electromagnetic velocimeter in a circulating water channel.
　　Various discharges with different water depths were tested. The Reynolds number (ReH) based on the height of structure and inflow velocity was ranging from 10000 to 59000. Among the structures used in this study, the permeable structure with porosity ε= 43.3% shows the maximum reduction of mean turbulence intensity and turbulent kinetic energy. In the recirculation region, the cases of permeable structure have smaller reverse velocities, compared to the case of non-permeable structure due to the bleed flow passing through the structures. Moreover, the bleed flow elongates the recirculation region in the downstream direction. On the basis of experimental data and dimensional analysis, the recirculating length was ranging form 6.6 to 8.5 times of the height of structure in the cases of non-permeable structure. For the permeable structure withε= 34.9%, the recirculating length was ranging form 9.0 to 10.8 times of the height of structure. For the permeable structure withε= 43.3%, the recirculating length was ranging form 10.2 to 11.2 times of the height of structure.

中文摘要　I
Abstract　II
誌謝　III
目錄　IV
表目錄　VII
圖目錄　VIII
照片目錄　X
符號說明　XI
第一章 緒論　1
1-1 研究動機　1
1-2 水流通過透水結構物之型　1
1-3 研究目的　3
1-4 前人研究　3
1-5 本文組織　5
第二章 理論分析　7
2-1 結構物附近之流場結構　7
2-2 紊流之量度與分析-Reynolds 平均法則　7
2-3 ADV量測理論　10
2-4 渦度定義　12
2-5 結構物內部流量之計算　14
2-6 雷諾數及福祿數之定義　16
2-6-1 雷諾數　16
2-6-2 福祿數　16
第三章 實驗設備與實驗方法　17
3-1 實驗設備　17
3-1-1 人工試驗玻璃渠道　17
3-1-2 實驗儀器設備　19
3-1-3 三角堰之率定　21
3-1-4 消除雜訊　21
3-2 實驗佈置　22
3-3 實驗方法與步驟　24
3-3-1 方法　24
3-3-2 步驟　27
第四章 結果分析及比較　34
4-1 平均速度　34
4-1.1 縱向平均速度　35
4-1.2垂向之平均速度　36
4-2紊流強度　37
4-2-1 縱向及垂向紊流強度　38
4-2-2 最大紊流強度　38
4-3 雷諾剪應力　39
4-4 紊流動能　39
4-5 渦度場　40
4-6 回流區長度估算　41
4-7 透水結構物內流量及流速分佈　42
第五章 結論與建議　66
5-1 結論　66
5-2 建議　67
參考文獻　68
附錄　70

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