三維二相流流場之數值與實驗研究

A Study of 3D two-phase free surface flows by numerical simulation and experimental measurements

孫銘寬(Ming-Kuan Sun)

指導教授 ： 鄧志浩

中原大學/工學院/土木工程研究所/博士(2013年)

https://doi.org/10.6840/CYCU.2013.00405

摘要

本研究建立了三維二相流最小平方有限元素法(TPLSFEM)之數值模式用以模擬自由液面流場，並且利用水工模型試驗量測驗證數值模擬的計算結果，潰壩與單階自由跌水問題為探討主題。求解流體假設為不可壓縮流場所描述之自由液面運動，自由液面與空氣接觸之處理是以流體體積法 (VOF) 與連續表面張力模式 (CSF)為基礎，將密度視為一個連續函數在此稱之 Color Function 以進行計算氣液接觸之二相流動問題之數值模擬。
本研究首先將潰壩流場與單階自由跌水的模擬與先前相關數值模擬結果實驗量測相同問題做定量比較，得到良好吻合的情形。再經由多次不同的流量對跌水後沖擊距離及迴水區水深所引發的相關問題，藉由數值模擬方式與實驗分析並觀察自由液面的流場變化歸納出相關公式。對於實際三維流場模擬於L型河道與部分潰壩觀察其現象，所得的結果更能說明與相關的數值實驗研究更佳的吻合。因此本文所獲數值模擬與實驗結果和文獻作比較驗證，顯示使用三維二相流最小平方有限元素法所得之結果，可以有效描述模擬具自由液面之三維問題，提供做為工程設計之參考。

關鍵字

二相流 ； 最小平方有限元素法 ； 單階自由跌水

並列摘要

In the study, the three-dimensional two-phase least-squares finite element method (TPLSFEM) has been established for the simulation of 3D two-phase free surface flows. The experimental setup for the verification of numerical simulations has also been built. The major topic is to investigate the dam-break and unit step free overfall problems. In this simulation, the flow is assumed incompressible, the volume of fluid (VOF) method and continuous stress force (CSF) models with association of color function are incorporated for the determination of the interface between water and air.
The formation of the model is carefully examined. The quantitative comparisons of numerical simulations of the dam-break and unit-step free overfall with previous numerical results and experimental measurements are shown to be in a good agreement. For numerical simulations with different flow rates, the reattached length, water height after the fall, are investigated in both qualitative and quantitative ways. Finally, for understanding more about the complicate phenomena truly 3-D case, the flow fields in L-shaped channel and Partial Dam Break Problem is simulated for different flow rates and geometric domains. It is shown in this study that the LSFEM can effectively simulate the 3-D flow phenomena. Our study will be helpful for the engineering designs and applications.

並列關鍵字

Least-Squares Finite Element Method ； Two-Phase Flows ； Unit Step Free Overfall.

參考文獻

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