Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/89415
標題: Experiments and Simulations of Live-Bed Pier Scour under Steady and Unsteady Flow Conditions
定量流及變量流作用下橋墩濁水沖刷深度之試驗與模擬
作者: 楊超傑
Chao-Chieh Yang
關鍵字: 動床;變量流;局部沖刷深度;橋墩沖刷;Live-Bed;Unsteady Flow;Local Scour Depth;Pier Scour
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摘要: 
本研究主要利用明渠水槽試驗,模擬動床條件之定量流況與變量流況橋墩前方沖刷深度隨時間變化之關係。試驗設計五組定量流沖刷每組試驗歷時三小時,其水流強度(平均流速與泥砂啟動流速之比值)分別為1.18、1.38、1.6、1.91及2.21,並由前述五組定量流水流強度設計而成之四組變量流沖刷每組試驗歷時五小時,包括前峰型、後峰型、對稱型(高洪峰)、對稱型(低洪峰)之變量流歷線,透過橋墩模型內架設之攝影機紀錄橋墩前方沖刷歷程。
除了以橋墩前方沖刷深度比較不同水流強度之定量流與不同峰型之變量流水槽試驗結果外,研究透過Hong等人(2014)發展之半經驗模式,模擬定量流沖刷歷線,並以疊加的方式將定量流沖刷歷線組合成不同峰型之變量流歷線,比較試驗沖刷歷線與疊加沖刷歷線兩者差異,研究結果顯示,在變量流試驗中隨著實驗的進行,當水流強度變小時水流作用力下降,導致砂丘推移速度變慢;而水流強度變大時水流作用力增加,加快砂丘落淤沖刷坑的速率,砂丘運移速率的差異會使模擬結果與試驗結果比較上有相位差的情形發生,而沖刷深度的模擬結果和試驗結果經計算比較後發現,誤差皆在10%以內,因此半經驗模式能在動床條件下,合理推算不同水流強度沖刷時橋墩前方沖刷深度發展之趨勢。

This paper aims to observe temporal evolutions of pier scour in live-bed condition in order to understand nature channel pier-scour. Five groups of steady flow experiments are designed in different flow intensities varied from 1.18 to 2.21. To find out the effects of unsteady flow on scour depth, different steady flow intensities were combined as four groups of unsteady flow experiments, including: (1) advanced hydrograph, (2) delayed hydrograph, (3) symmetric hydrograph and (4) symmetric hydrograph with low peak.Temporal evolutions of pier scour are recorded by camera set up in experimental pier.Unsteady flow scour depth hydrographs were verified by constant flow hydrograph in different flow intensities. All experiments were set in live-bed requirement to approach the nature condition of pier-scour during flood. This research also use a semi-empirical modle proposed by Hong (2014) to calculate the experiment pier-scour depth varied with time. The semi-empirical equation was used to calculate the change of scour depth obtain from experiments. This research also combined steady flow scour depth hydrograph to discuss whether it can simulate unsteady flow hydrograph or not. Simulation and experiment result may have phase difference because of the difference between dune migration rate. As result,scour depth error calculate from simulation and experiment are less than 10%.The propose model gives reasonable explanation on the variations of cylinder pier-scour depth with time under unsteady flow.
URI: http://hdl.handle.net/11455/89415
其他識別: U0005-2608201516015700
Rights: 同意授權瀏覽/列印電子全文服務,2015-08-27起公開。
Appears in Collections:水土保持學系

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