圖書典藏及影音數位平台

天然河道水系多屬蜿蜒，而蜿蜒渠段水理泥砂之運動型態較為複雜，且常為致災亟需保護之處。主要乃因水流通過彎道時，二次流造成凹岸處河床淘刷及凸岸處之淤積，進而造成凹岸之崩塌退縮以及凸岸之淤積成長；此外，於支流匯入主流之河道交匯處，由於流量變化、動量交換與能量型態轉換，導致流況轉為複雜，往往造成水位劇烈之變化，且河道輸砂能力也受到水流變化影響，可能導致河床過度的沖刷或淤積，進而危及河川水工結構物。因此，對於河道之整治與治理規劃考量，實需針對蜿蜒河道之二次流效應或水流交匯所造成的局部沖淤行為進一步分析探討。 本計畫將發展一擬似三維動床模式，該模式需能兼具全河段、局部底床沖淤及河岸退縮等模擬功能，藉以模擬探討蜿蜒河道中所產生的二次流效應及側入流影響所引起的局部沖刷行為。綜觀國內、外相關水槽試驗，目前雖有蜿蜒渠道動床相關試驗數據可供模式比對，卻無較完整之岸壁退縮水槽試驗。因此本計畫將進行一系列相關蜿蜒渠槽試驗，提供模式發展建置與比對測試，以探討模式之適用性，解析蜿蜒渠道底床沖淤及岸壁沖刷之發展機制及行為，最後將模式應用於實際案例，以展現模式之實用性。

The purpose of this study is to examine channel stability which is in-fluenced by the migration process of a meandering channel by investigat-ing sediment transport mechanism with compound cross sections through characteristics analysis and field investigation. Theoretical analysis on an application study is employed to annotate the guidelines for hydraulic en-gineers in their designing and planning. The annual report of this research project analyzed the channel sta-bility of a meandering channel on channel stability through a bank failure experiment. Moreover, this study also developed a quasi-3D model based on a vertical-horizontal splitting (VHS) method to analyze the complex field in open channel. In horizontal, the surface elevation and depth-averaged velocity components are computed by 2D depth-averaged model. In vertical, the 3D velocity profile of Navier-Stokes equations is assumed equal to the depth-averaged velocity plus the deviation of veloc-ity profile, and then the vertical governing equations can be hence derived by subtracting the 2D depth-averaged equations to the 3D Navier-Stokes equations. Finally, the quasi -3D model was applied to a specific reach in Youluo River. Simulation results including bend flow, lateral flow and complex field near spur dike are also presented in the reort.The outcome of this study on Youluo River River will be valuable for future improve-ment projects.