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A Study on Fishway Roughness Increase
SHIUAN, WEI YUH
Z style fishway
In this research, three discharges for different slopes of fishway and different forms of sand dunes placement were used to simulate the flow conditions in the fishway and to investigate the relationships among depth , velocity , specific energy , and Manning's roughness n. Besides, sediment-loaded experiments also were conducted to examine the deposit condition at the downstream of sand dunes in the fishway.
From the results of model experiment, it is clear that the Manning's coefficient increased when sand dunes were placed in the fishway, therefore, the flow depth also increased but flow velocity decreased. The increment of Manning's coefficient enlarged apparently for the fishway with steep slope. Besides, the fishway with sand dunes placed within at equal spaces had the largest increment of Manning's n, about two to four times larger than the fishway with only one sand dune placed.
An important result found from the experiment was that sediment deposition in the fishway only happened for those with slope of 1:10. This discovery also reveals an important message for the design of this new Z style fishway.
This study focused on the inner structure of new Z style fishway. With sand dunes placed within the fishway, flow conditions were improved significantly and no serious sediment deposition in the fishway. The research result indicated a feasible design of inner structure for new Z style fishway.|
中文摘要 本研究採用三種渠槽流量，針對不同的魚道坡度及不同的砂丘板施作方式，模擬防砂壩水流流入魚道內，對水流的深度、流速、比能及曼寧n值進行探討，並於試驗完成之後做初步的加砂試驗，探討魚道內加了砂丘板之後的淤砂情形。 經試驗資料分析得知魚道內隨著砂丘板的施作，其曼寧n值亦跟著增大；因此，水深也將變大；而流速也將減緩，尤其較陡的魚道其增加幅度也較大較明顯。另外，當連續等間距的施作砂丘板時，其曼寧n值增大的幅度將產生更佳的效果，約為一塊砂丘板的3~5倍。 至於加砂的部份，隨著流量的增加，除坡度為1：10的魚道內仍有砂石的淤積外，坡度為1：8及1：6的魚道內完全沒有淤砂的現象發生，這對新式Z型魚道無疑是一項重要的訊息。 本試驗對新式Z型魚道內部之構造加以探討，經砂丘板的施作之後，使得進入新式Z型魚道內之水流，其流況有明顯的改善，且沒有嚴重之淤砂現象，如此一來對於往後新式Z型魚道之內部設計，將提供一個不錯的方法。
|Appears in Collections:||水土保持學系|
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