本文以實驗及數值計算分析超臨界流況下，橋墩受水流沖擊所造成的墩前湧波，探討橋墩尺度對振幅、頻率的影響；實驗於亞臨界流況下，利用超音波速度剖面儀(UVP)量測墩前速度場分佈，進一步探討墩前射流之分離位置及流場中頻率的特性，並透過數值模Truchas分析墩前射流位置及渦流分佈。實驗結果顯示，沖擊高度與上游福祿數呈正比之關係；UVP 能有效量測邊界層厚度及墩前渦流尺寸；透過數值模式，能進一步分析細部流場變化，如：渦度分佈、底床剪應力。本研究之結果可幫助於瞭解亞、超臨界流況中墩前沖擊高度與上游福祿數的關係，可供相關工程設計之參考。 Bow waves in front of cylindrical piers under different flow conditions, especially supercritical flows, are explored in this study by employing both flume experiments and 3D numerical simulation. An ultrasonic velocity profiler (UVP) is used to measure the downward/upward flow right in front of the pier, and the downward flow and the stagnation point along the profile are also measured. The magnitudes and the frequencies of bow waves are analyzed by image analysis. The vortex sizes are mainly determined by pier diameter alone. The dimensionless amplitude of bow waves is proportional to the square of upstream Froude numbers. The numerical simulations for piers in shallow water show that the shear stresses on the floor exhibit maximum value at the downstream sides, which is due to pier-induced surface drawdown and wake separation.
