在河道中設置橡皮壩(Rubber dam)攔河堰來抬高水位，做為防洪、取水及防治河床沖刷之用，且可藉由壩頂部的水深計算流量。但洪水來臨時，這些橡皮壩便會受到洪水的沖擊，因此必須對橡皮壩所受的水流沖擊力和流場有深入地瞭解，以避免橡皮壩之損壞。本篇論文便是採用大渦流模式與流體體積分率法計算圓柱形橡皮壩上、下游的流況和壩體的受力，模擬結果並與水槽實驗量測得之自由水面及表面壓力比較，以驗證大渦流模式的正確性。再利用數值模式進行一系列的模擬，檢視福祿數、阻滯比、上下游水深比等參數對圓柱形橡皮壩的阻力與升力係數之影響。數值模擬結果顯示：模式預測之阻力係數隨水深比變大而變小，升力係數隨水深比並沒有顯著的變化。此外，由模擬結果可計算水流過圓柱形橡皮壩的流量係數，接近前人 Matthew (1963) and Heidarpour & Chamani (2006)所預測之流量係數，但當下游水深變大，產生迴水效應時，流量係數便會偏離前人公式。本研究之成果可應用在圓柱形橡皮壩的設計與管理。
;Rubber dams are widely used around the world for irrigation, water supply, flood control, scouring protection. This study integrated a Large Eddy Simulation (LES) model and the Volume of Fluid (VOF) method to investigate the free surface flows around a circular rubber dam. The simulation results were verified by the results of laboratory experiments. The numerical model was then used to examine the influences of Froude number, Reynolds number, depth ratio and blockage ratio on the hydrodynamic forces and discharge coefficients of the rubber dam. The results revealed that the drag coefficient decreased as the depth ratio increased. The flow rates over the crest of the dam were used to compute the discharge coefficients, and the computed discharge coefficient was different from the formula suggested by Matthew (1963) and Heidarpour & Chamani (2006) due to the backwater effect. The results of this study can be used for the structure design of circular rubber dam.
