臺灣博碩士論文加值系統

隨著電腦科技的演進，固液二相流模擬日漸受到重視。本研究以電腦數值方法進行固液二相流計算平台開發與實際應用，利用CFD-ACE計算流體力學軟體以有限體積法求解Navier-Stokes方程式計算流體，採用的模型為Flow Module；固體方面，分別採用表面質點近似法與拉格朗日法，模型分別為Macro Particle Module與Spray Module，因此在求解問題時有兩種耦合方式可求解固體與液體間交互作用行為。前者，在顆粒碰撞時壓力場將會發散，在研究中證實利用自行發展的碰撞模型可以避開此問題使數值穩定讓模擬順利運作，使用此種耦合方式計算效率較低但可以微觀角度探討二相流問題；後者，用來實際模擬微米尺度顆粒在微流道中聚集效應，以往認為此效應主因剪力梯度與壁面效應引起的側向力造成顆粒側向位移至平衡位置所造成，壁面效應與剪力梯度都與顆粒體積造成周圍流場不對稱有關，但在Spray Module中並無考慮顆粒體積，也無法解析出顆粒周圍的流場卻能模擬出與實驗相同的趨勢，並根據數值實驗的結果發現，在微米尺度下，邊牆效應以及剪力梯度的效應並不明顯，故相較之下流場才是主導顆粒側向位移的主因，使用此種耦合方式計算效率較高但只能觀察系統整體巨觀行為。

With the advance of the computer technology, simulation of the two-phase for the solid-liquid system has been emphasized. In this research, we develop a computation platform for the solid-liquid system, which utilizes the flow module of the CFD-ACE software to solve the Navier-Stokes equations. There are two coupling methods to solve the interactions between the solid phase and the fluid phase. To solve the motion of solids, we use the surface maker point approach and the Lagrangian particle-tracking method.
In the former method, the pressure field blows up when two particles collide. To resolve this issue, we develop a collision model to calculate the two-phase flow motion that resolves individual micro particles. We use the latter method to simulate particle focusing in micro channels. Previous literatures pointed out that the main factors of lateral forcing to move the micro particles to their equilibrium positions are shear gradient and wall effect. These two forcing factors account for the asymmetry of the flow field surrounding the particle. However, while the spray module does not consider the particle volume and the surrounding flow field, simulation results qualitatively agree with the experimental observations. Moreover, according to a separate numerical experiment, perturbations of velocity and pressure field due to the presence of a single particle are not obvious. We find that the background hydrodynamic forcing is the dominant cause of the lateral displacement. In conclusion, in simulating particle focusing in micro channels, flow perturbation due to the pressure of individual particles may not be important, and the spray module can obtains the relevant approximation. However, the spray module can only be used to observe the macroscopic behavior.

目錄
第一章 緒論 1
1.1研究動機與背景 1
1.2文獻回顧 1
1.2.1 鞘流聚集 2
1.2.2 主動的非鞘流聚集 5
1.2.3 被動的非鞘流聚集 8
1.3論文架構 17
第二章 數值方法 18
2.1 CFD-ACE使用流程 18
2.1.1 前處理器(pre-processor) 18
2.1.2 求解器(solver) 19
2.1.3 後處理器(post-processor) 20
2.2 網格生成 20
2.2.1 網格分類 20
2.2.2 數值擴散 21
2.2.3 網格品質 21
2.3 數學模型 22
2.3.1 Flow Module 22
2.3.2 Macro Particle Module 23
2.3.3 Spray Module 25
2.4 數值解法 26
2.4.1 分離解法(segregated) 26
2.4.2 空間離散方法 28
2.4.3 時間離散方法 32
2.4.4 壓力與速度耦合關係之處理 33
第三章 固液二相流計算平台開發 38
3.1顆粒碰撞種類 43
3.2顆粒碰撞模型推導 44
3.3程式設計流程 47
3.4導入顆粒碰撞模型之結果 51
第四章 固液二相流計算平台應用 57
4.1 在多孔微流體通道中引起慣性升力與渦旋使顆粒達到連續聚集 57
4.1.1 理論背景 57
4.1.2 實驗配置 61
4.2利用Flow Module耦合Macro Particle Module進行二維模擬 62
4.2.1 模擬配置 62
4.2.2 結果與討論 62
4.3利用Flow Module耦合Spray Module進行三維模擬 66
4.3.1 模擬配置 66
4.3.2 理論分析 67
4.3.3 結果與討論 70
第五章 結論 79
5.1 總結 79
5.2 未來與展望 80
參考文獻 82

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