二相流模式探討明渠流在不規則底床運行之現象

Simulation of Open Channel Flows on a Ueven Bottom by a Two-Phase Flow Model

鄭雅允(Ya-Yun Cheng)

指導教授 ： 鄧志浩

中原大學/工學院/土木工程研究所/碩士(2003年)

https://doi.org/10.6840/cycu200300612

摘要

摘要
本文利用二相流(Two-Phase Flows)模式探討明渠水流在不規則底床運行之現象，採用最小平方法(LSFEM)之數值模式求解常見的明渠流況在不可壓縮流場所描述之自由液面的運動，以尢拉慣性座標描述自由液面動力與運動邊界條件，以流體體積法(VOF)為基礎配以一連續函數在此稱之Colour Function；將密度視為一個連續函數的變化對自由液面氣液接觸之二相流動問題進行數值模擬。
首先以最小平方有限元素法(LSFEM)模擬地面具障礙物之潰壩流場觀察其流場與壓力分佈，再以具兩矮檻模式驗證不規則底床具自由液面明渠流的水面流線和水深的變化，在明渠流動中不易量測的震盪現象，以具跌落結構的矩形溝渠池模擬。數值模擬結果經與實驗研究驗證比較極為相近，在自由液面交界面之捕捉有相當良好的成果。最後研究案例的應用以本模式仔細地探討湧流撞擊底床具不同的長寬高比值障礙物觀察其自由液面流場及壓力分佈之複雜變化。

關鍵字

明渠流 ； 最小平方有限元素法 ； 二相流

並列摘要

ABSTRACT
This paper use the two-phase flows model to investigate the open channel flow motion on a uneven bed. The least-squares finite element method is adopted for the numerical simulation of the incompressible free surface problems. The dynamic and kinematic boundary conditions of free surface are described in an Eulerian coordinate system. In this simulation, a volume of fluid method with association of colour function is applied for the determination of the interface between liquid and gas.
The model is verified by two experimental measurements, first, the dam break flow over a block is simulated for monitoring the flow and pressure distributions; second, a surge flow over the uneven bed is studied to justify the free surface profile and oscillation phenomena. The simulation results are in good agreement with the experimental measurement. For the free surface propagates on a solid block with different sizes and heights, the free surface variations and pressure distributions are carefully investigated in this study.

並列關鍵字

Open Channel Flow ； Two-Phase Flows ； Least-Squares Finite Element Method

參考文獻

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