臺灣博碩士論文加值系統

本研究探討方板隨攻角變化的尾流特徵與氣動力性能。將方板放置在一低速風洞中，使用煙線流場可視化及熱線風速儀與負荷計進行量測與分析，探討流場現象、速度分佈、紊流強度、渦旋流逸頻率與氣動力性能等的特性。由煙線流場可視化法可以發現，方板表面的邊界層及尾流區的行為包括分離、分離泡、分離再接觸、迴流區與渦旋流逸等現象，這些流場特性對於氣動力有一定的影響。利用簡單的相似理論對尾流區非穩態結構的頻率尋求史卓數、洛斯柯數與雷諾數之間的函數關係與物理機制，結果可以將渦旋流逸的實驗數據相關成有用的無因次方程式。使用負荷計量測方板氣動力性能的結果，得到類似於機翼氣動力行為的特性，在雷諾數40000時，攻角在28˚左右會有機翼氣動力中失速的現象產生。在高雷諾數時的升、阻力變化與一般參考資料可以尋獲的少量數據相近，顯示自製的二維負荷計及去偶合技巧的功能並不遜色。在低雷諾數時以及非90˚攻角時的氣動力性能提供了補足了方板在過去研究結果的缺漏。

Surface flow behaviors, wake flow characteristics, and aerodynamic forces of a square plate at various Reynolds numbers and angles of attack were experimentally studied in a low speed wind tunnel. Flow patterns on the surface of the plate and in the wake were identified by using the smoke-wire flow-visualization technique. The velocity profiles, turbulent intensities and vortex-shedding frequencies were measured by an one-component hot-wire anemometer. Aerodynamics lift and drag were measured with a home-made two-component load cell. The results revealed the characteristics in the flow filed, e.g., boundary layer separation, separation bubble, reattach, recirculation wake and vortex shedding. The flow behaviors were found to be closely-related to the aerodynamic performance of the flat plate. Applying simplified similarity theory to the momentum equation, the relationships between the Roshko number and the Reynolds number as well as that between the Strouhal number and the Reynolds number were characterized. Experimental results of the vortex shedding frequencies were found to follow the analytical derivation. Measurements of the aerodynamic loads showed that the stall at ReD=40000 occurred at the angle of attack of 28˚. The measured lift and drag coefficients at high-Reynolds number regime coincided with previous results obtained by many investigators. The aerodynamic performances obtained in this study at low Reynolds numbers and angles of attack other than 90˚ provided more information for the square plate aerodynamics.

目錄
摘要 i
Abstract ii
致謝 iii
目錄 iv
符號索引 vi
表圖索引 vii
第一章 緒論 1
1.1 研究動機 1
1.2 文獻回顧 2
第二章 實驗設備、儀器與方法 5
2.1 風洞 5
2.2 煙線流場可視化 6
2.3 頻譜分析儀與數據擷取系統 10
2.4 邊界層速度分佈、紊流強度與動態頻率的 11
.偵測
2.5 氣動力量測 11
2.5.1 負荷計 11
2.5.2 二個負荷計合用於二維量測時的去偶. ..合技巧 13
. .2.5.3 將垂直與平行力轉換為升力與阻力 15
2.6 重要參數的定義 16
第三章 流場特徵 18
3.1 煙線流場可視化 18
3.2 邊界層分離、再接觸與分離泡的行為 20
3.3 尾流速度分佈與紊流特性 22
3.3.1 尾流速度分佈 23
3.3.2 紊流特性 25
第四章 尾流渦旋逸放頻率 29
4.1 渦旋流逸頻率的量測與分析 29
4.2 渦旋流逸的頻率特性 32
第五章 氣動力性能 35
5.1 不同雷諾數下的氣動力性能 35
5.2 隨攻角改變的氣動力性能 38
第六章 結論與建議 40
6.1 結論 40
6.2 建議 41
參考文獻 43
附錄一 46
表圖索引
表圖編號 表 圖 名 稱 頁次
表2-1 白蠟油質點的主要特性 48
圖2-1 實驗儀器設備配置示意圖 49
圖2-2 風洞測試段氣流的基本特性 50
圖2-3 實驗模型、座標系統與控制機構示意圖 51
圖2-4 (a)負荷計受力應變示意圖，(b)惠斯頓電橋與電壓輸出示意圖 52
圖2-5 負荷計施以正向力獨立校正後的曲線圖 53
圖2-6 去除偶合交互作用的電腦程式之流程圖 54
圖2-7 Load cell 氣動力量測與升阻力合成示意圖 55
圖3-1 ReD=5000時，使用煙線流場可視化技術拍攝不同攻角θ之流場照片 56
圖3-2 ReD=10000時，使用煙線流場可視化技術拍攝不同攻角θ之流場照片 57
圖3-3 ReD=20000時，使用煙線流場可視化技術拍攝不同攻角θ之流場照片 58
圖3-4 ReD=10000時，使用煙線流場可視化技術拍攝低攻角時，隨角度變化的流場細部照片 59
圖3-5 ReD=20000時，使用煙線流場可視化技術拍攝低攻角時，隨角度變化的流場細部照片 62
圖3-6 ReD=40000時，使用煙線流場可視化技術拍攝低攻角時，隨角度變化的流場細部照片 65
圖3-7 ReD=40000、θ=0˚時，於不同下游位置之平均速度分佈圖 68
圖3-8 ReD=40000、θ=15˚時，於不同下游位置之平均速度分佈圖 69
圖3-9 ReD=40000、θ=30˚時，於不同下游位置之平均速度分佈圖 70
圖3-10 ReD=40000、θ=45˚時，於不同下游位置之平均速度分佈圖 71
圖3-11 ReD=40000、θ=60˚時，於不同下游位置之平均速度分佈圖 72
圖3-12 ReD=40000、θ=75˚時，於不同下游位置之平均速度分佈圖 73
圖3-13 ReD=40000、θ=90˚時，於不同下游位置之平均速度分佈圖 74
圖3-14 ReD=40000、θ=0˚時，於不同下游位置之紊流強度變化圖 75
圖3-15 ReD=40000、θ=15˚時，於不同下游位置之紊流強度變化圖 76
圖3-16 ReD=40000、θ=30˚時，於不同下游位置之紊流強度變化圖 77
圖3-17 ReD=40000、θ=45˚時，於不同下游位置之紊流強度變化圖 78
圖3-18 ReD=40000、θ=60˚時，於不同下游位置之紊流強度變化圖 79
圖3-19 ReD=40000、θ=75˚時，於不同下游位置之紊流強度變化圖 80
圖3-20 ReD=40000、θ=90˚時，於不同下游位置之紊流強度變化圖 81
圖4-1 ReD=40000時，在下游方向X/D=5處，於不同攻角θ時，使用熱線風速儀所量測到的典型尾流訊號圖 82
圖4-2 ReD=10000時，在下游方向X/D=5處，於不同攻角θ時，所量測的尾流訊號頻譜圖 83
圖4-3 ReD=20000時，在下游方向X/D=5處，於不同攻角θ時，所量測的尾流訊號頻譜圖 84
圖4-4 ReD=40000時，在下游方向X/D=5處，於不同攻角θ時，所量測的尾流訊號頻譜圖 85
圖4-5 ReD=60000時，在下游方向X/D=5處，於不同攻角θ時，所量測的尾流訊號頻譜圖 86
圖4-6 ReD=80000時，在下游方向X/D=5處，於不同攻角θ時，所量測的尾流訊號頻譜圖 87
圖4-7 ReD=100000時，在下游方向X/D=5處，於不同攻角θ時，所量測的尾流訊號頻譜圖 88
圖4-8 (a)不同自由流速時，頻率f隨θ角度的變化圖(b)不同θ攻角時，頻率f隨自由流速的變化圖 89
圖4-9 在不同攻角時，Rod隨迎風面雷諾數的變化 90
圖4-10 在不同攻角時，Std隨迎風面雷諾數的變化 91
圖5-1 在不同攻角時，阻力FD隨風速uw的變化圖 92
圖5-2 在不同攻角時，升力FL隨風速uw的變化圖 93
圖5-3 在不同攻角時，CD值隨雷諾數的變化情形 94
圖5-4 在不同攻角時，CD值隨雷諾數的變化情形 95
圖5-5 不同物體形狀的阻力係數 96
圖5-6 在不同攻角時，CL值隨雷諾數的變化情形 97
圖5-7 在不同攻角時，CL值隨雷諾數的變化情形 98
圖5-8 ReD=40000時，阻力FD隨攻角θ的變化情形 99
圖5-9 ReD=40000時，升力FL隨攻角θ的變化情形 100
圖5-10 ReD=40000時，CD值隨攻角θ的變化情形 101
圖5-11 ReD=40000時，CL值隨攻角θ的變化情形 102
圖5-12 ReD=40000時，升阻比隨攻角θ的變化情形 103

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