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研究生： 陳昱翔
Chen, Yu-Hsiang
論文名稱： 自由車手周遭流場結構探討與風洞實驗數據分析
Investigation on the topology of a flow around a cyclist and analysis of wind tunnel experimental data
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： 2022
畢業學年度： 110
語文別： 中文
論文頁數： 81
中文關鍵詞： 自由車 、風洞實驗 、流場可視化 、軸渦 、減阻 、表面粗糙元
外文關鍵詞： Cyclist, wind tunnel, axial vortex, drag reduction, roughness pattern
相關次數： 點閱：87  下載：14 
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    • 現今自由車發展已趨於成熟，比賽的結果乃是分秒之差，因此如何有效的提升騎乘效率與降低騎行阻力是近年來許多研究人員不斷努力的目標。而在騎乘過程中風阻佔據整體阻力高達九成之多，在這其中騎乘者的阻力又在佔七成左右，因此研究騎乘者周遭的流場對減低風阻有顯著的幫助。而本研究主旨在使用風洞與水洞對騎行者模型做流場可視化實驗，依此探尋騎行者身旁的流場現象，並透過改變粗糙元會使流場發生層紊流轉換的原理，改變模型上局部區域的表面粗糙度，觀察其對整體阻力的影響。
    本研究中包含水洞與風洞的縮尺模型流場可視化實驗與全尺模型壓力訊號實驗與阻力量測實驗。縮尺流場可視化實驗是為了要觀察模型表面渦流流場的捲動方式;而全尺模型實驗則是透過壓力訊號的量測佐證渦旋的捲動型態，以及阻力的變化。
    縮尺模型實驗是使用1/5縮尺且姿勢為下彎把(Dropped position)的模型，模型的踩踏角以左腳腳踝角度為定義。通過流場可視化實驗觀察到車手模型的手部與大腿區域有著與傾斜圓柱類似的軸向渦流產生，而在小腿上觀察到類似圓柱現象的雙分離線;另外，在模型的頸部可以觀察到因為耳廓而引起的凹穴流，以及凹穴流隨後向背部捲動而形成的V字型油膜堆積線。
    爾後在全尺模型研究中，透過上手臂的壓力訊號與縮尺模型實驗的結果做比對，將上手臂區域劃分為，分離前、分離後與軸流接觸區域三個部分。接著再透過相關性分析，證實隨著雷諾數的升高手臂上的流場會逐漸影響到背部的流場。接著透過改變局部粗糙元的方式，發現上手臂的粗糙元改變對於減阻效果最顯著，而如果在大腿與下手臂區域改變粗糙元，則會導致阻力上升。
    透過模型表面流場的研究可以了解人體流場的基本型態，並通過這些基本型態的現象研究那些型態的流場是有助於阻力的減少。這將能夠為之後減阻研究提供一個參照。而未來若是想要精進選手訓練，將可以依此為依據針對每位選手的姿勢特性去做調整。

    Reduction of aerodynamic drag is an important topic in the development of a bicycle racing. It is extremely vital to study the flow field phenomenon on the surface of a cyclist. As the wind flows over the human body, the flow separation phenomenon will appear on the surface. The purpose of this research is to study the aerodynamic characteristics of cyclists observed in the water channel and the wind tunnel using flow visualization methods. Cyclist models used in water channel and wind tunnel testing were based on a real male cyclist and printed using a 3D printer.
    Flow visualization technology was employed to observe the flow phenomenon around the arms, thighs and calves of the cyclist model. It is found that there are vortices rolling along the axial direction at the arms and thighs, double separation lines appear at the lower legs and a cavity flow in the neck, etc. Then, the surface pressure coefficient of the model is measured by the full-scale model wind tunnel experiment to verify the flow mode of the flow field here.
    Through these research methods, we can better understand the structure of the flow field around the cyclist, and further achieve the purpose of drag reduction.

    摘要 I ABSTRACT III 目錄 IX 圖目錄 XII 符號索引 XVI 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 自由車空氣動力學 5 1.3.3 傾角圓柱 8 1.3.4 表面粗糙度 10 1.3.5 前期研究 12 第二章 實驗設備與架設 15 2.1 實驗模型 15 2.1.1 模型幾何與座標定義 15 2.1.2 模型壓力孔編號 16 2.2 表面粗糙元 17 2.3 風洞與水槽介紹 18 2.3.1 低速開放噴流式風洞 18 2.3.2 循環式水槽規格與速度校正 18 2.3.3 內政部建築研究所環境風洞(簡稱ABRI風洞) 19 2.4 實驗設備 21 2.4.1 手提式壓力校正器 21 2.4.2 壓力轉換器 22 2.4.3 皮托管 23 2.4.4 溫度計 24 2.4.5 測力載台 24 2.4.6 加速規 25 2.4.7 水平校正儀 27 2.4.8 資料擷取系統 28 第三章 研究方法與實驗步驟 30 3.1 全尺模型風洞實驗 31 3.1.1 荷重元校正與力量量測 31 3.1.2 風速與壓力量測校正 33 3.1.3 車手模型不同部位粗糙元實驗 33 3.2 縮尺模型流場可視化實驗 34 3.2.1 油膜法 34 3.2.2 點墨法 36 3.2.3 染液注射法 37 3.3 實驗參數與分析 38 3.3.1 雷諾數(Reynolds number) 38 3.3.2 壓力係數(Pressure coefficient)與擾動壓力 38 3.3.3 阻力係數(Drag coefficient)與擾動阻力 39 3.3.4 決定係數(Coefficient of determination) 40 3.4 訊號分析 40 3.4.1 相關性分析 40 3.4.2 快速傅立葉轉換 41 第四章 結果與討論 42 4.1 縮尺模型風洞可視化實驗 42 4.1.1 油膜實驗結果 42 4.1.2 雷諾數效應 47 4.2 縮尺模型水洞可視化實驗 48 4.2.1 軸渦現象 49 4.2.2 小腿上的雙分離線 54 4.2.3 頸部渦旋與背部V型分離線 55 4.3 全尺模型風洞實驗 58 4.3.1 全尺實驗重現性 59 4.3.2 阻力量測訊號品質 62 4.3.3 壓力係數與相關性分析 64 4.3.4 模型部分區域粗糙度改變對流場影響 69 第五章 結論與未來建議 75 5.1 結論 75 5.2 未來建議 77 第六章 參考資料 78

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