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研究生： 曾建勳
Tseng, Chien-Hsun
論文名稱： 全尺與縮尺自行車手模型流場結構與風洞數據研究
Research of the flow structure and experiment data on full and small scale cyclist model
指導教授： 苗君易
Miau, Jiun-Jih
學位類別： 碩士
Master
系所名稱： 工學院 - 航空太空工程學系
Department of Aeronautics & Astronautics
論文出版年： 2019
畢業學年度： 107
語文別： 中文
論文頁數： 121
中文關鍵詞： 自行車手空氣動力學 、下彎把握姿 、風洞實驗 、縮尺模型 、流場可視化
外文關鍵詞： Cyclist aerodynamics, Dropped position, Wind tunnel experiment, Scale model, Flow visualization
相關次數： 點閱：183  下載：9 
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    • 隨著自行車競賽的發展，降低空氣動力阻力成了提升競賽成績的關鍵，因此深入的了解其流場狀態及實驗問題才能在未來進行有效率的改善。本研究以兩次全尺車手模型風洞實驗做為出發點，探討均勻來流流經下彎把姿勢(Dropped position)之車手模型所造成的周圍流場現象以及風洞實驗數據討論，並配合電腦平均模擬(RANS)獲得更詳細的流場訊息，例如表面流動分離位置、表面剪切方向、渦流結構發展、表面壓力、阻力…等，另外也使用相同幾何之1/5縮尺模型於小型風洞及水槽分別進行尾流量測及流場可視化實驗，研究雷諾數差異對於此模型的流場影響。
    首先由全尺模擬結果與全尺風洞實驗數據比對發現，兩次風洞實驗量測之表面壓力係數確實受到模型架設的角度差異而造成影響，但整體趨勢仍然相近，不過並不會造成阻力係數明顯的變化，因此仍然有其他未知原因導致阻力數據差異較大，不過從壓力量測的結果可推測兩大型環境風洞皆具有不錯的風場品質。接著透過縮尺實驗與全尺模擬結果相互比較後發現，雷諾數對此模型的表面流場特徵與尾流大型渦流結構發展的影響並不劇烈，表示縮尺模型實驗已具有相當好的相似性與參考價值。最後透過各雷諾數下的結果得知，阻力係數隨著雷諾數升高而逐漸下降，並從模擬結果能觀察到肩膀及軀幹側面分離線緩慢的隨雷諾數後移，此現象與圓柱於預臨界區時類似，表示未來有可能在特定位置安排不同表面粗糙度，提早在低雷諾數進入如圓柱的預臨界區狀態而延後流動分離位置，進而降低阻力係數。
    對於尾流發展的平均結果，在不同雷諾數下人體左右腰部靠近臀部位置皆會產生一明顯螺旋分離焦點，並且在尾流區發展成一較穩定的連貫渦流結構，此位置渦流也造成下流相當程度的動量損失，借助模擬結果也能發現尾流之連貫渦流結構中心位置壓力較低，提供了不小的渦阻。此外，兩側頸部位置也產生一對明顯的渦流對，並將外側流體動量捲入背部中央，導致背部分離線呈現一個V型的分佈，或許未來也能從改變渦流結構的發展進行減阻。

    As the progressing of the bicycle race, reducing aerodynamic drag has become the key to improving the performance of the competition. Therefore, to have an effective improvement in the future, a further understanding of the surrounding flow field conditions and experimental problems can be significant. In this study, we start with two wind tunnel experiment data on full-scale cyclist models, analysing the flow characteristics and aerodynamic performance with a cyclist model at the dropped position. The computational fluid dynamics is used to collect more detailed flow field information, such as surface flow separation, limiting streamline, vortex structure development, etc. Also, by using the same geometry 1/5 scale model in a small wind tunnel, evaluated by wake structure, drag, and visualization experiments with the use of water channel, carried out to study the flow field similarity between the scale model and the full-scale model.

    摘要 I Abstract III 誌謝 VIII 目錄 IX 表目錄 XV 圖目錄 XVI 符號索引 XXII 第一章 緒論 1 1.1 前言 1 1.2 研究動機與目的 2 1.3 文獻回顧 3 1.3.1 鈍形體流體力學 3 1.3.2 自行車空氣動力學 6 第二章 實驗設備與架設 12 2.1 實驗模型 12 2.1.1 模型後處理與支撐結構 12 2.1.2 模型幾何與坐標定義 13 2.2 風洞介紹 14 2.2.1 內政部建研所環境風洞(簡稱風洞A) 14 2.2.2 馮˙卡門流體動力學研究所低速風洞(簡稱風洞B) 14 2.2.3 低速開放式自由噴流風洞(簡稱風洞C) 15 2.3 風洞A實驗設備 16 2.3.1 皮托-靜壓管 16 2.3.2 轉子式風速計 16 2.3.3 溫度計 16 2.3.4 手提式壓力校正器 17 2.3.5 壓力轉換器 17 2.3.6 大型一維力平衡儀與放大器 17 2.3.7 資料擷取系統 18 2.4 風洞B實驗設備 18 2.4.1 皮托管 19 2.4.2 壓力轉換器 19 2.4.3 二維力平衡儀 19 2.5 風洞C實驗設備 20 2.5.1 皮托-靜壓管 20 2.5.2 壓力轉換器 20 2.5.3 熱線測速儀系統 20 2.5.4 三維移動機構 21 2.5.5 熱線測速儀量測位置 22 2.5.6 小型一維力平衡儀與放大器 22 2.5.7 資料擷取系統 22 2.6 低速循環式水槽 22 2.6.1 水槽規格與流速校正 23 2.6.2 視流工具 23 第三章 研究方法與步驟 24 3.1 風洞A及B實驗步驟 24 3.2 風洞C實驗步驟 25 3.2.1 阻力量測 25 3.2.2 空流場量測 26 3.2.3 熱線測速儀分析 26 3.3 流場可視化 27 3.3.1 染液注射法 27 3.3.2 油膜法(Oil film) 28 3.3.3 點墨法 28 3.4 實驗參數分析 29 3.4.1 雷諾數定義 29 3.4.2 壓力係數 29 3.4.3 壓力擾動 30 3.4.4 車手阻力係數 30 3.4.5 平均壓力係數比較方法 32 3.4.6 決定係數(Coefficient of determination,R2) 33 3.4.7 無因次化剪應力 34 3.4.8 基本紊流流速統計量 34 3.4.9 熱線測速儀無因次化方法 34 3.4.10 尾流截面流向渦度 35 第四章 Fluent電腦輔助流體力學分析 37 4.1 紊流模型 38 4.2 渦流辨識 39 4.3 Case1 :水槽實驗模擬 41 4.3.1 計算幾何 41 4.3.2 網格建置 42 4.3.3 邊界條件 42 4.3.4 求解方法與收斂準則 43 4.4 Case2 :風洞A實驗模擬 44 4.4.1 計算區域 44 4.4.2 網格建置 44 4.4.3 邊界條件 45 4.4.4 求解方法與收斂準則 45 4.5 Case3 :模型於2度及4度俯仰角模擬 45 第五章 結果與討論 46 5.1 縮尺模型初步流場討論 46 5.1.1 平均流動分離線 46 5.1.2 表面漸進流線 47 5.1.3 煙線 48 5.1.4 自行車架影響 48 5.2 風洞實驗數據探討 49 5.2.1 模型表面平均壓力係數 49 5.2.2 阻力量測結果 50 5.3 風洞實驗數據與模擬結果驗證及比較 51 5.3.1 無俯仰角模擬結果與實驗數據之比較 51 5.3.2 俯仰角度對表面壓力係數影響 52 5.3.3 俯仰角度對阻力係數影響 52 5.3.4 使用背部壓力係數進行阻力值判斷 53 5.4 兩尺度模型近表面特徵觀察 54 5.5 尾流發展探討與比較 54 5.5.1 迴流區觀察 54 5.5.2 無因次化流向平均速度分布 55 5.5.3 總紊流強度分布 55 5.5.4 無因次化流向平均渦度分布 56 5.5.5 渦流辨識與尾流區域壓力分佈 56 5.6 雷諾數效應對近表面流場影響 57 5.7 擾動壓力係數探討與比較 58 第六章 結論與未來建議 62 6.1 結論 62 6.2 未來建議 63 參考文獻 65 表格 70 圖片 72

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