本文主要研究筐網群複合橋墩，筐網群與橋墩在不同間距下，對橋墩周圍流場之變化。於定床試驗中，利用ADV流速儀量測筐網群複合橋墩之速度場。以探討筐網群與橋墩在不同間距下，其墩前入流、墩側側流及尾渦的變化。並與水流通過橋墩之速度場進行比對，配合曾玟義(2012)現地試驗之資料，以瞭解筐網群複合橋墩，其橋墩周圍流場之變化，對橋墩周圍沖淤之影響。
由試驗結果可知，水流通過筐網群時，筐網間會產生加速流流動，而該流動會顯著的影響筐網群複合橋墩的墩前入流。墩前水流強度與筐網群與橋墩之間距成正比。無因次筐網群與橋墩之間距L/d=0~3，墩側水流的強度與筐網群與橋墩之間距成反比。L/d=4則因速度回復效應，墩側水流增強。橋墩後方存在卡曼渦列，除無因次筐網群與橋墩之間距L/d=0.5，筐網群與橋墩束縮外，尾渦的強度與筐網群與橋墩之間距成反比。而在橋墩前設置筐網群，墩前水位會較未設置筐網群時低。經對比曾玟義(2012)之試驗，發現墩側水流強度與墩前回淤高度成反比。

This paper studied the flow field around the permeable-cylinder group, ahead of a circular pier of diameter (d), at different spacings (Ls and Lw as shown in Fig. 3). Experiment had been carried out in a fixed-bed flume and the measurement of velocity profiles at three cross sections was made by using acoustic Doppler velocimetry (ADV). From these measured results, flow velocity distribution in front of the pier was affected by the distance (L) between the permeable-cylinder group and the pier. Except for dimensionless distance L/d = 0.5, the wake flow intensity decreases with the increase of this distance. Comparison with the result obtained by Zeng(2012), intensity of flow around cylinder was inversely proportional to deposition height in front of cylinder.

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