矩形銳緣堰流量係數研究

矩形銳緣堰通常設置於量水堰出口以量測流量，並以流量係數C_d去修正理論公式與實際公式差值。本研究彙整前人研究及室內實驗，推算流量係數。由於流量係數與開口寬度b_c、靜水池寬度B、水深H、尾檻高度P有關，因此將銳緣堰分為開口寬度b_c等於靜水池寬度B或小於兩種；再透過實驗，推求b_c＜B之流量係數C_d及有效流量係數C_d。分析發現，當b_c=B，Bos（1989）、Swamee（1988）及Rouse（1936）所發展之不同範圍之無因次水深H／P之C_d公式，可銜接成為連續關係，當H／P趨近0，最小C_d = 0.602，當10.4＜H／P＜10.9，得最大C_d = 1.189，經由台北市上游七處水文站分析，因上游河道流量變化大，建議採隨H／P而變之流量係數公式；當b_c＜B，流量係數隨無因次水深H／P變大而增加，無因次開口寬度b_c／B減少而增加，本研究推導之流量係數公式，適用於無因次水深0.63≤H／P≤9.66、深寬比0.18≤H／b_c≤9.66，及無因次開口寬度0.0083≤b_c／B≤0.2917之量水堰。

關鍵字

量水堰；矩形銳緣堰；流量係數

並列摘要

A rectangular sharp-crested weir is usually set at the outlet of a weir to measure flow quantity: the flow coefficient Cd is obtained experimentally to correct the difference between theoretical and practical discharge. Considering the large variety of rivers upstream of Taipei City, this study combines the previously reported data with our laboratory experimental data to develop a flow coefficient formula. The flow coefficient is related to the width of the opening bc, the width of the still basin B, the depth of the water H, and the height of the tail sill P; accordingly, the flow coefficient of a sharp-crested weir can be divided into two types: bc = B and bc ＜ B. After the analysis of previous data, the formulas of Bos (1989), Swamee (1988), and Rouse (1936) can be combined to establish a formula for Cd varied by H/P for bc = B. When H/P approaches 0, the minimum Cd value is 0.602, and when 10.4 ＜ H/P ＜ 10.9, the maximum Cd value is 1.189. This equation is particularly suited to the upstream river because the flow was noted to change considerably when seven hydrological stations upstream of Taipei City were analyzed. For bc ＜ B, the flow coefficient increases when H/P increases and bc/B decreases. The formula of the flow coefficient derived in this study applies to 0.63≤H/P≤9.66 , 0.18≤H/b_c≤9.66 and 0.0083≤b_c/B≤0.2917.

並列關鍵字

measuring weir ； sharp-crested weir ； discharge coefficient

國際替代計量

矩形銳緣堰流量係數研究

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