本研究使用主、支渠水平渠底與單一支渠三十度相交之水工模型，進行亞 臨界分流流場實驗；支、主渠渠寬比分為1：1、1：2、1：3，每一渠寬比進行七組流量比實驗。於支主渠下游端以一活動檔板，使主支渠下流流況形成一自由跌水，並控制主、支渠下游水深、福祿數及流量；藉以探討不同流量比之下各個物理參數之意義。影響分流流況因素眾多，如主支渠渠寬比、渠底坡度、主支渠交接角度、分流轉彎處平滑度等。由實驗數據得知：在相同渠寬比下，主渠上游均勻斷面之主渠下游平面寬度隨主渠上下游之流量比增加而遞增；主、支渠分流區之平均流向角隨流量比增加而減小，而隨支、主渠渠寬比減小而增加。在分流區水流受到支渠迴流區及束流區影響，造成較大之能量損失，而隨支、主渠渠寬比減小而增加。支渠迴流區最大深度平均寬度隨著主渠上下游之流量比增加而遞增；其再觸長度亦隨主渠上下游之流量比增加而遞增。形狀參數隨支、主渠流量比增加而增大。當固定一支主渠流量比下，會有一最大主渠下游福祿數值存在，且有一相對應之最小支渠水深值。 This study presents the experimental results for 30° divided sub- critical open-channel flow. The branch- to main-channel width ratios were 1, 1/2, and 1/3. For each run, 7 discharges were conducted in the ex- periments. The experimental results showed that the flow is fully de- veloped and uniformly distributed at 4 channel-widths upstream of dividing point. It also showed that the flow angle at the interface increases with increasing discharge ratio while the re-circulation width and the reattachment length decrease. The downstream- to upstream-depth ratio in the main channel depends on the discharge ratio and downstream Froude number. The depth ratio increases with increasing discharge ratio and decreases with increasing downstream Froude number. In addition, the energy loss coefficient increases with increasing width ratio.
