臺灣博碩士論文加值系統

本研究主要為探討三維自由液面流場受到筐網圓柱之影響。首先，以k–ε標準紊流模式搭配體積分率法進行單根筐網圓柱之流場模擬，並利用孔隙介質流模式計算水體流經筐網圓柱時所受到的阻滯效應。經由模擬結果與物理試驗結果之比較，發現兩者趨勢頗為一致，顯示數值模擬在單根筐網圓柱之流場變化上具有一定程度的準確性。接著，在相同入流流況與相同圓柱直徑的情境下，本研究進行多組不同孔隙率的流場模擬，並定義臨界壓力去估算出不同孔隙率的筐網圓柱後方的保護範圍。我們將擁有最大保護範圍之孔隙率稱為最佳孔隙率，經由模擬結果發現最佳孔隙率會位於孔隙率0.43左右。
最後，將單根筐網圓柱案例擴展到單排筐網圓柱之案例，我們進行單排實心圓柱與單排筐網圓柱之流場比較，以及不同根數的筐網圓柱對於流場之影響。由模擬結果得知，實心圓柱的阻水效應大，圓柱後方的流速分佈紊亂，相反的，筐網圓柱後方的流速分佈卻十分穩定，顯示筐網圓柱比實心圓柱更能穩定流場。比較不同筐網圓柱根數的流場變化發現，根數越多之流場，後方的低速區範圍有明顯增大之趨勢。

The main objective of this research is to investigate the effect of porous cylinders on flow patterns. The standard k–ε turbulence model and the volume of fluid method (VOF) are used to simulate 3-D free surface flows. The resistant force generated by porous cylinders is performed by porous media theory. The computed results are verified by the available experimental data and are in consistent with the experiment data. In addition, we are concerned with how a large area is protected behind the porous cylinder, so a critical pressure is defined to estimate the protection area. Through several kinds of porosity are used in simulations, it is found that there is the largest protection area when the porosity is around 0.43. Thus, we call it as the optimal porosity in this study.
Finally, we apply our model to flows past two kinds of singled-row cylinders, porous cylinders and solid cylinders. From the numerical results, we can conclude that flows past porous cylinders are more stable than those past solid cylinders. The number of cylinders is in proportional to their protection area.

謝誌 2
摘要 I
Abstract II
目錄 III
表目錄 V
圖目錄 VI
符號對照表 IX
第一章 緒論 1
1.1前言 1
1.2研究目的 2
1.3文獻回顧 2
第二章 理論模式 5
2.1流場控制方程式 5
2.2紊流模式k–ε 6
2.3邊牆函數 7
2.4孔隙介質流模式 8
2.5體積分率法 9
第三章 數值方法 12
3.1數值模擬架構 12
3.2有限體積法 12
3.3控制方程式的離散 13
3.4收斂條件 14
3.5邊界條件設定 14
第四章 模式驗證 18
4.1實心圓柱驗證 18
4.2孔隙圓柱驗證 20
4.3驗證結果與討論 21
4.4孔隙區域與孔隙跳躍之比較 22
第五章 模式應用 42
5.1最佳孔隙率的探討 42
5.2單排圓柱的探討 44
5.2.1不同根數之筐網圓柱的流場流速分佈比較 45
5.2.2筐網圓柱與實心圓柱的流場流速分佈比較 46
第六章 結論與建議 64
6.1結論 64
6.2建議 65
參考文獻 66

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