Turbidity Current Plunge Mechanism Analysis and Simulation System Application

異重流潛入機制分析與模擬系統研發應用

10.6937/TWC.201912_67(4).0001

李豐佐(FONG-ZUO LEE)；賴進松(JIHN-SUNG LAI)；譚義績(YIH-CHI TAN)；張明瑞(MING-JUI CHANG)；陳鵬安(PENG-AN CHEN)；林國峰(GWO-FONG LIN)

Turbidity current ； Densimetric Froude number ； Plunge point location ； Woody debris ； Simulation system ； 異重流 ； 密差福祿數 ； 潛入點 ； 漂流木 ； 模擬分析系統

台灣水利

67卷4期（2019 / 12 / 01）

1 - 15

英文

In recent years, sediment flows into reservoirs with frequent flooding, due to extreme weather and torrential rainfall in reservoir catchments. High gradient slopes and large flow velocities in watersheds also increase inflow sediment yield into reservoirs. Therefore, reservoir sedimentation seriously affects water resources allocation, while maintaining reservoir capacity is a current vital issue. Turbidity current venting is the main method used in Taiwan hydraulic desiltation strategies. The Shihmen reservoir is selected as a research area in this study because it has completed measurement data. Based on field measured data of vertical velocity and sediment concentration distribution, the turbidity current performance is confirmed in the field by behavior calibration. We adapt a Densimetric Froude number and a theoretical equation to estimate plunge point locations during typhoon events. According to the sediment concentrations derived from the regression relationship between discharge and sediment yield, and measured data, the plunge point locations are calculated with differences in plunge point areas. In addition, based on water color differences at plunge point locations, and woody debris aggregation spots, the Densimetric Froude number of the Tsengwen reservoir and Shihmen reservoir are determined to be 0.68 and 0.64, respectively. This study also developed a display and simulation system to analyze turbidity current movement. The system applies the discharge and sediment yield regression relationship, and the Densimetric Froude number estimation formula, to estimate plunge point location and turbidity current movement. The head velocity and arrival time can be predicted in advance for turbidity current venting. Immediate data on reservoir desiltation can provide useful information especially applicable to the Amouping desilting tunnel and Dawanping desilting tunnel. Future studies that incorporate rainfall runoff prediction for turbidity current movement prediction will improve Shihmen reservoir desiltation operations.

近年來受到極端氣候影響，暴雨及強降雨事件頻傳，加上臺灣集水區坡陡流急，使得大量水砂流入水庫造成嚴重淤積，因此如何維持現有庫容量已是刻不容緩的課題，而臺灣水庫防淤技術首重異重流排砂，因此本研究以目前資料最為齊全之石門水庫為主要研究區域，根據現地量測之垂向流速與泥砂濃度分布，判讀石門水庫異重流是否發生之依據，同時亦採用異重流密差福祿數經驗公式及異重流潛入點前後理論關係式估計潛入點發生位置，透過利用霞雲站迴歸公式及用羅浮站實測泥砂濃度數據計算之密差福祿數歷線，分析異重流潛入點位置之斷面僅有1～2個斷面差異性，此外，根據異重流潛入點前後之清渾交界顏色不同或是利用現場漂流木聚集位置進行潛入點判定及密差福祿數計算，獲得曾文水庫及石門水庫異重流潛入點密差福祿數值分別約為0.68及0.64。本研究亦建製介面展示與操作的功能，建構異重流模擬分析系統，結合降雨預報、入流流量與輸砂量關係式，以及異重流潛入之密差福祿數，則可利用異重流模擬系統進行異重流運移分析之預報，事先估算異重流發生潛入位置、運移速度及到達壩前時間，對於未來石門水庫利用阿姆坪防淤隧道、大灣坪防淤隧道及排砂隧道（電廠一期改善工程）之即時排砂操作，將有立即且實用之價值。

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