臺灣博碩士論文加值系統

本文應用大尺度渦流法並結合拉氏顆粒追蹤法及four-way coupling兩相處理方式來模擬雷諾數644之垂直渠道紊流場，並於流場中放入不同材質顆粒群進行個別紊流統計量之分析，在顆粒與壁面碰撞方面分別使用光滑壁面模式與Sommerfeld & Huber(2003)所提出的壁面粗糙度模式進行模擬計算，並將光滑壁面模式結果與他人使用雷諾平均方程式搭配蒙地卡羅法直接模擬顆粒碰撞方法所得結果做比較驗證，然後進一步在此種低體積分率下，具不同材質顆粒群碰撞之垂直渠道紊流場，找出影響顆粒運動行為的主要的因素。
肇因於大尺度渦流法與雷諾平均方程式在紊流的計算模式不同，造成本研究與Hsu(2005b)計算結果有所出入，但其在顆粒的各種紊流統計量上有相同的趨勢。在不同材質顆粒之負載紊流場使用光滑壁面模式下，顆粒雖然會受顆粒與顆粒間的碰撞與顆粒碰撞壁面的影響，顆粒在流場中的運動行為還是主要決定於其Stokes No.值。
於壁面粗糙模式下，壁面粗糙度造成垂直壁面擾動速度大幅增加而使顆粒往主流中心區移動，降低了 較低顆粒在近壁低速區的累積，同時加強了顆粒在垂直壁面方向混合的能力，進而改變顆粒於流場中的分佈狀況，顆粒在流場中的運動行為將不再完全由Stokes No.值主導，還必須考慮壁面粗糙度因素所造成的影響。

Particle-laden turbulent channel flow using the four-way coupling approach at Re=644 , loaded with different particle groups, is studied numerically using the Lagrangian particle tracking (LPT) method coupled with large eddy simulation (LES). Turbulence statistics loaded with different particle groups are analyzed. Two particle-wall models are applied to this study. One is the smooth wall model while the other is the rough wall model developed by Sommerfeld and Huber (2003). In order to verify the computation results and to find the major factors affecting the behavior of particle motion with the smooth wall model in turbulent channel flow, the results in this study are compared with those of others work using a Reynolds-averaged Navier-Stokes (RANS) model for the turbulent flow motion together with the direct simulation Monte Carlo (DSMC) method for inter-particle collisions.
Due to different modeling approaches between in LES and RANS，it leads to some differences in quantity of the computational results. Nevertheless, most results of turbulence statistics obtained with ether LES or RANS are in qualitatively agreement. It is found that the behavior of particle motion with smooth wall model in the turbulent channel flow is primarily affected by the value of despite considering the particle-wall and inter-particle collisions.
Taking into considerations of rough wall model, the effect of wall roughness in the computations strengthens the wall-normal particle velocity fluctuations. As a result, particles tend to move from the near-wall region to the center region. It leads to decrement of particle accumulation in the near-wall region as compared to the case considering the smooth wall model. The wall-normal particle mixing capability is enhanced which results in the redistribution of particles in the channel. The behavior of particle motion in the turbulent channel flow should be, thus, dependent on not only the value of but also the wall roughness level.

書名頁
簽名頁
授權書
簽署人須知
誌　謝
摘　要 i
Abstract iii
目　錄 v
表目錄 vii
圖目錄 viii
符號說明 xii
第一章　緒論 1
1.1 前言 1
1.2 文獻回顧 3
1.3 研究目標 8
第二章　大尺度渦流法紊流場中之物理模式與數值方法 10
2.1 流體運動 10
2.2 氣相數值方法 12
2.3 顆粒運動 16
2.4 顆粒之間碰撞 19
2.5 顆粒運動的數值方法 23
第三章　不同顆粒之選擇與壁面模式 25
3.1 不同顆粒之選擇 25
3.2 壁面模式之選擇 25
第四章　結果與討論 30
4.1 氣相模擬 30
4.2 顆粒模擬 33
4.3 不同顆粒結果 35
4.4 應用Sommerfeld & Huber’s模式 42
第五章　結論與建議 50
5.1 結論 50
5.2 建議 51
參考文獻 52
自述

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