Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/33079
標題: 單株倒伏植株水理型態與沖刷特性之試驗研究
Experiments of Hydraulic Mechanics and Local Scour Characteristics around the Tilted-Single Plant
作者: 許懿尹
Hsu, Yi-Yin
關鍵字: 植物水理
plant hydraulics
沖刷坑型態
紊流動能
scour hole
turbulent kinetic energy
出版社: 水土保持學系所
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摘要: 台灣的河濱高灘地上常種植經濟作物,如香蕉及甘蔗等,而近年來受極端氣候影響,集水區內之豪大雨經匯流後,進入河川形成洪水,而當河道中的植物受洪水侵襲後常發生倒伏之情形。欲了解這類型植物受洪水侵襲時對底床及水流的影響,本研究使用不鏽鋼管模擬植物受水流衝襲後之情形,將鋼管彎折成不同角度模擬植物倒伏型態進行試驗。試驗過程中利用ADV流速儀測量不鏽鋼管周圍的流場分布情形,並使用雷射測距儀量測沖刷坑的三維地形資料,探討不鏽鋼管之不同彎曲型態其底床沖淤發展情形、周圍流場及紊流強度。 研究結果顯示,彎管越趨倒伏,沖刷坑深度及沖刷坑與堆積丘的體積越小。彎管下方的水流受彎管箝制影響,水流離開彎管後會形成一射流情形,且在彎管周圍的垂向(W方向)與水流方向(U方向)流速呈現極度不穩定狀態。水流在彎管下方時,受彎管影響所形成的尾跡渦流會受彎管所箝制而難以消散。本研究中,紊流動能最大可達19左右,主要發生在彎管本身的周圍,而彎管周圍的高強度紊流動能分布自3至18之間不等,且紊流動能呈現綿延分布並沿著彎管周圍發展,當彎管越倒伏時,紊流動能越均勻綿延分布。在本研究之水流條件下,結構物所引起的紊流動能影響範圍約達結構物周圍約2至3cm。結果顯示紊流強度僅與水流條件相關,當彎管越趨倒伏時,其對底床變化的影響越小,而周圍紊流強度分布會隨著彎管的位置降低而跟著降低其分布的區塊。
In recent years, the heavy rainfall converges into river in the watershed and becomes the flooding because of the extreme weather. In Taiwan there are lots of economic crops in floodplain, such as banana and sugar cane. The flood induces the crops to tilt. The tilt crops change the form of riverbed and the flow condition. The study investigated the scour hole, the flow field, and the turbulent kinetic energy (TKE) around the tilt single plant. The experiment used the stainless steel tube to simulate the situation that the plant is affected by flow. Results of an experimental study on clear-water scour at a control set and three different angles (tube with bed; degree of 90, 60, and 45) of the bended tube in uniform bed sediments under steady flow are presented. The velocity field around the tube was measured by Acoustic Doppler Velocimeter (ADV), and we also measured the topography of scour holes by laser range finder. According to the experimental results, the depth and volume of scour hole is consider with the angle when the tube became more tilt. A jet flow after the flow leaving the tube because the flow was clamped by the tube, and the cast-off vortices and wake was also clamp down by the tube. The vertical and streamwise velocity was extremely unstable around the tube. The maximum of TKE occurred around the tube of the set 45 degrees, the value is about 19, and the high TKE area around the tube, the value is roughly 3 to 18 in all sets. TKE distributed along the tube, when the tube gets more tilt, TKE becomes more stretching. In the flow conditions of this study, TKE exists at roughly 2 to 3cm around the tube. Therefore, the experimental results demonstrate that the tube became more tilt, the fewer effect reflect on riverbed. TKE related with flow condition, and TKE’s distribution changes with the tube.
URI: http://hdl.handle.net/11455/33079
其他識別: U0005-3107201222595500
文章連結: http://www.airitilibrary.com/Publication/alDetailedMesh1?DocID=U0005-3107201222595500
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