前人對堰流的流量估計方式常常都以美國墾務局所出版的”Design of Small Dam”中的流量係數估算，本篇研究主要針對此估計方式以設計手冊中提供之臥箕堰設計方式，進行建模，在同樣的參數P/Ho之下，進行流量差量的探討。
而在測試臥箕堰流量之模擬中，發現整體而言，在模擬的網格大小案例中，除了堰高(P)=0m之外，其數值模擬流量與依照”Design of Small Dam”所計算出於設計水頭流況下之設計流量相差約1.9%~3.1%之間，整體FLOW-3D數值模擬解，皆大於設計流量，與Kim及Park (2005)及Savage及Johnson (2001)所做出之結果相似。
在非設計水頭流況之模擬流量也比設計流量大，於上游水頭越小時差量越大，但在上游水頭越大時差量越小，可達0.4%，整體模擬流量大於設計流量。在傾斜堰頂之模擬中，模擬流量大於設計流量1~2%。
最後，本研究最後再以曾文水庫建設誌-竣工圖所提供的溢洪道及左右側牆進行建模，加入105年水庫淤積報告之庫區高程，匯入FLOW-3D對曾文水庫溢洪道於原設計最高洪水位EL.232.5m時之放流量重新進行估算及討論，而本研究發現於可能的最經濟的網格設置發現其模擬值相較於設計流量大約大了2%。
以上述網格設置量測到之接近渠道斷面平均總水頭，用來只模擬接近渠道及溢洪道部分，因為模擬區域較小，縮小了網格大小，其模擬流量與設計流量差量縮小至1.65%。
由模擬結果來看，整體而言FLOW-3D之臥箕堰流量模擬應比設計流量大，一般約是1~2%。本研究也針對閘門流進行了二維的流量模擬，發現當網格尺寸越小時，其模擬流量與設計流量相當接近，但有比設計流量小的趨勢。

In order to understand the characteristics of weir flowrate simulation, this paper discuss how the difference between modeling discharge and design discharge calculated by design manual. The discharge over the weir has been often calculated with weir flow formula by the discharge coefficient in the “Design of Small Dam” which published by US Bureau of Reclamation (USBR).

The research is mainly based on building model by design manual to simulate discharge over weir by FLOW-3D, under the same parameters P/HO, discussing the difference with weir flow formula. In the simulation cases of most of grid sizes for the design head, the modeling discharge is larger about 1.9%~3.1% than design flowrate, the results are similar with the result by Kim and Park (2005)、Johnson (2001).

In the cases for other than the design head, the modeling discharge is also lager than designed discharge. This difference decrease as upstream head up, increase as upstream head up decrease. In all the cases, modeling discharge is larger than design discharge.
This research also discuss the influence for ogee-shaped crest with sloping upstream face, testing the upstream face of the crest is sloped 1:1, the modeling results are also larger than design flowrate.

Finally, build the Tsengwen Reservoir model to simulate the free flow discharge when the water level elevation is El.232.5m and radial gate discharge. Compare the difference between modeling result and Tsengwen Reservoir Spillway discharge rating curve. To account for the long simulation time for 3-D simulation of calculating the flowrate under a radial gate. This paper run 2-D discharge simulation for radial gate flow to calculate discharge of per unit width and compare the results with the one calculated by equation of discharge under a radial gate in “Design of Small Dam”.

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