近年來建築設計不只往高度上發展，同時也追求跨度的延展，隨著建築技術進步與材料強度的提升，屋蓋的跨度由數十米發展為數百米，重量也由每平方公尺減少至幾十公斤的薄膜結構。而設計此類大跨度屋蓋結構，風的載重是影響其安全性與舒適度的重要考量之一，本研究即以計算流體力學模擬大跨度圓頂屋蓋在平滑流場中受風特性，並與文獻之風洞實驗結果比較。
本研究內容分為兩部分：第一部份為網格選定，在嘗試幾種不同計算域切割與網格繪製後，做一個簡單的初步試算，與實驗結果比較，選定一套網格後加密模型周圍計算域後，進行第二部分模擬。第二部分為半球在Re=6.6×104和Re=2×106兩個雷諾數流場受風模擬，每個雷諾數在計算域入流5D的地面又分為兩種不同邊界條件設定：可滑動界面（slip wall）和不可滑動界面（non-slip wall）。
模擬結果顯示，低雷諾數流場半球子午線上平均與擾動壓力分佈與實驗值誤差較大，主要原因有二：一是透過可視化發現半球尾跡區之分離泡超過網格加密區塊，過大的網格造成其模擬的精準度不足；二是流體在半球表面分離之前所形成的邊界層為層流邊界層，分離之後方轉為紊流邊界層，使用Fluent的基本設定是否能夠完整模擬如此複雜的流體變化尚有待證實。
高雷諾數的流場模擬顯示，不同地面邊界層設定所得結果相近，半球子午線上除迎風面擾動壓力分佈略大於實驗值，其他位置平均與擾動壓力與實驗都很吻合，擾動風壓頻譜亦如是，顯示數值模擬所得之半球體空氣動力特性與風洞實驗結果吻合。但是風壓分佈機率模擬結果比實驗值分佈集中，說明其風壓極值不足以作為局部構件設計的參考依據。由數值模擬所得之水平向昇力係數頻譜可觀察到數個峰值，顯示半球體後方並無單一的渦旋剝離頻率。透過可視化看到流體流經半球後方渦旋並無明顯交替作用，但會隨著昇力係數的變化左右擺動。

This study uses LES to simulate the aerodynamic characteristics of hemispherical dome in a smooth approaching flow field. The accuracy of numerical simulation was verified firstly by comparing with the wind tunnel measurements. Then the details of the aerodynamics of the dome were presented in this thesis. Prior to study the dome aerodynamics, several schemes of the grid system and numerical parameters were examined to determine the optimal ones for this study. The numerical simulation in this thesis can be categorized into two parts:  the aerodynamics of dome in two Reynolds numbers, Re=6.6×104 and 2×106.
In the case of Re=6.6×104, the mean and RMS pressure coefficients on the center meridian are noticeably deviated from experiment data. The numerical error may be caused by two reasons. The first probable source of error is that the separation bubble in the wake region extent beyond the mesh refined area. The second one is more subtle. At subcritical Reynolds number, the boundary layer developed over the dome surface is of laminar nature; it transits to become turbulent flow after separated from dome surface. Whether the basic setting of CFD tool, ANSYS-FLUENT, is apt to such a complex numerical simulation is to be confirmed.
As for the second case, Re=2×106, the mean and RMS pressure coefficients on the center meridian agree well with experiment data except near the front stagnation area. The power spectral densities of the numerical simulated pressure fluctuations also agree with wind tunnel measurements satisfactory. Only the probability densities of the numerical simulation exhibit deviations from the wind tunnel data. It indicates that although the current numerical simulation scheme can reproduce the hemi-spherical dome’s aerodynamic quite well; it is still insufficient to generate the small scale turbulence that contributes to the pressure peaks. The lift force spectrum exhibits multiple peaks; which indicate the complexity of the vortex shedding in the horizontal plane. The time history of the vorticity further demonstrate that there exists no clear interaction between two separated free shear layers of the two opposite side of the dome; however, the wake flow show rather periodic sway synchronized with the variation of lift force coefficient.

第一章 緒論	3
1-1前言	3
1-2研究動機	3
1-3研究內容	4
第二章 基礎理論與文獻	5
2-1流體特性	5
2-1-1黏滯性	5
2-1-2雷諾數	5
2-1-3層流與紊流	5
2-2流體流經鈍體行為	6
2-2-1邊界層	6
2-2-2分離	6
2-2-3尾跡	7
2-2-4渦散現象	7
2-3流體流經半球行為	7
2-4氣動力參數	8
第三章 計算流體力學	10
3-1 計算流體力學的模擬步驟	10
3-2 Fluent使用介紹	11
3-2-1 網格	12
3-2-2數值方法	13
3-2-3紊流模式	15
3-2-4邊界條件	20
3-2 分析設備	20
第四章 問題描述及計算過程	21
4-1 實驗設置	21
4-2數值計算流程	21
4-3計算域	22
4-3-1 網格繪製	22
4-3-2 初步模擬設定	23
4-3-3 初步模擬結果比較	23
4-4平滑流場模擬設定	24
第五章 結果分析	25
5-1雷諾數6.6×104的模擬結果	25
5-1-1風壓係數	25
5-1-2擾動風壓頻譜	25
5-2雷諾數2.0×106的模擬結果	26
5-2-1風壓係數	26
5-2-2擾動風壓頻譜	28
5-2-3 壓力分佈	28
流場可視化分析	28
第六章 結論與建議	30
參考文獻	32
表4-1	34
表4-2	34
表5-1	35
圖2-1 圓管中色絲流況，(A)層流；(B)過度階段；(C)紊流	36
圖2-2 邊界層的形成	36
圖2-3 邊界層分離之過程	37
圖3-1 文獻[16]，數值模擬步驟	37
圖3-2 FLUENT[30]提供各種網格元素	38
圖3-3 FLUENT在速度及壓力求解疊代方法的選用視窗	38
圖4-1 內政部建築研究所所屬台南縣歸仁鄉之風動實驗館風洞配置圖	39
圖4-2 傅博士平滑流場實驗配置圖	39
圖4-3 數值計算流程圖	40
圖4-4 計算域俯視圖和側視圖	40
圖4-5 半球使用帶狀切割之不同視角圖	41
圖4-6 半球十字帶狀分割之不同視角圖	41
圖4-7 半球帶狀切割空間網格生成	42
圖4-8 半球使用MAP+PAVE網格分割	42
圖4-9 半球使用MAP網格分割	43
圖4-10 使用MAP+PAVE網格計算域的俯視圖和側視圖	43
圖4-11 使用MAP網格計算域的俯視圖和側視圖	44
圖4-12 邊界條件設定	44
圖4-13 RE=2×106之半球子午線上(A)平均風壓係數(B)擾動風壓係數分佈。	45
圖4-14 網格加密之計算域	46
圖4-15 計算域的邊界條件	46
圖5-1-1 RE=6.6×104之半球子午線上(A)平均風壓係數；(B)擾動風壓係數分佈。	47
圖5-1- 2 RE=6.6×104之半球子午線上壓力梯度分佈	48
圖5-1- 3 RE=6.6×104擾動風速頻譜(A)Θ=90；(B)Θ=220；(C)Θ=710；(D)Θ=810；(E) Θ=990；(F) Θ=1450	49
圖5-2-1 RE=2.0×106之半球子午線上(A)平均風壓係數(B)擾動風壓係數分 佈。	50
圖5-2-2 RE=6.6×104之半球緯度60度(A)平均風壓係數；(B)擾動風壓係數 分佈。	51
圖5-2-3 RE=2.0×106之半球前入流段向量圖(A)SLIP WALL；(B)NON SLIP WALL	52
圖5-2-4 RE=2.0×106之半球前流體形成之渦旋(A)SLIP WALL；(B) NON SLIP WALL	52
圖5-2-5 RE=2.0×106之半球子午線上的壓力梯度	53
圖5-2-6 RE=2.0×106擾動風力頻譜，(A)Θ=100；(B) Θ=400；(C) Θ=800；(D) Θ=1000；(E) Θ=1100；(F) Θ=1200 (G) Θ=1400 (H) Θ=1600。	54
圖5-2-7 RE=2.0×106之壓力分佈圖(A)Θ=100；(B) Θ=200；(C) Θ=300；(D) Θ=1000；(E) Θ=1200；(F) Θ=1400。	55
圖5-2-8 RE=2.0×106之半球表面平均風壓分佈(A) 實驗值；(B) SLIP WALL；(C) NON SLIP WALL	56
圖5-2-9 RE=2.0×106之半球表面擾動風壓分佈(A) 實驗值；B) SLIP WALL；(C) NON SLIP WALL	56
圖5-2-10 RE=2.0×106之流體流過半球後的分離現象(SLIP WALL)	57
圖5-2-11 RE=2.0×106之流體流過半球後的分離現象(NON SLIP WALL)	57
圖5-2-12 RE=2.0×106之升力係數歷時(SLIP WALL)	58
圖5-2-13 RE=2.0×106之部分升力係數歷時(SLIP WALL)	58
圖5-2-14 RE=2.0×106之Z向渦度圖(SLIP WALL)	60
圖 5-2-15RE=2.0×106之Z向渦度圖(SLIP WALL)	61
圖5-2-16 RE=2.0×106之半球Z向不同高度切線示意圖	62
圖5-2-17 RE=2.0×106之半球Z向不同高度的水平壓力向量(SLIP WALL)	62
圖5-2-18 RE=2.0×106之半球Z向不同高度的水平壓力向量(NON SLIP WALL)	63
圖5-2-19 RE=2×106之半球表面升力係數頻譜(SLIP WALL)	63
圖6-1 RE=6.6×104 之半球下游速度向量子午線切面	64
圖6-2 RE=6.6×104 之半球下游流線子午線切面	64

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