Delft3D在蜿蜒河道水流模擬之應用研究

Abstract

天然河道水系多屬蜿蜒，而蜿蜒渠段水理之運動型態較為複雜，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，因此針對蜿蜒河道之二次流效應實需進一步分析探討。 緩彎、急彎與連續彎實驗案例為三種具代表性之蜿蜒渠道案例，本研究以荷蘭Delft大學WL Delft Hydraulics研究開發的一套軟體-Delft3D模擬蜿蜒河道，使用兩種不同的紊流模式(零方程式及k-ε)模擬探討彎道中的流場變化與二次流現象，利用de Vriend and Koch (1977)緩彎案例、Rozovskii (1961)急彎案例、Almquist and Holley (1985)連續彎案例以及經濟部水利署水利規劃試驗所（WRPI，2012）南勢角連續彎案例之物理模型所量測出的實驗值來檢定模式之正確性。此四案例除實驗完善亦有Resed3D模擬結果(洪聖翔，2011；林怡君，2013；楊宗原，2014)，可供相互驗證二次流等現象，並顯示Delft3D在蜿蜒河道及交匯流場模擬之合理性及可靠性。

Natural river course drainage systems are primarily meandering channel, in which the water motion patterns are more complicated. The major reason is that as current flow through the curve, the secondary flows resulted in downcutting in the concave banks and deposition in the convex banks, respectively. As a result, further analyses and researches on the effects of secondary flows upon meandering channel flow are essential. The experiments of smooth curves, rapid curves, and consecutive curves are three examples of meandering channel. This research was based on an meandering channel simulation program, Delft 3D, developed by WL Delft Hydraulics from Delft University of Technology, Netherlands, using two different turbulence models, zero equation and k-ε, to simulate the change in flow fields and phenomenon of secondary flows. The experimental results from four examples, de Virend and Koch (1977) smooth curves, Rozovskii (1961) sharp curves, Almquist and Holley (1985) consecutive curves and the WRPI(2012)Nanshijiao consecutive curve were used to verify the accuracy of the model. Beside proper, competent procedures, the Resed3D simulation results (Hong，2011；Lin，2013；Yang，2014) had also not only provided a two-way verification for the above four examples, but exhibited the rationality and reliability of Delft3D on simulating meandering channel and converging flow fields.