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研究生： 馮美儂
Vonthron, Manon
論文名稱： 自行車車架空氣動力性能值模擬
CFD study of cross-section foils performances in cycling aerodynamics
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： 2015
畢業學年度： 103
語文別： 英文
論文頁數： 125
外文關鍵詞： Cycling aerodynamics, CFD, Flow separation, Aerodynamic coefficients
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    • In cycling aerodynamics, many kinds of foils have been used on bicycles during the History (cylinder, tear drop or NACA). The aerodynamic performances in low Reynolds number are studied because of the early flow separation and vortex generation.
    From a scientific paper presenting a new foil which has remarkable aerodynamic performances, the project has been launched. The aim is to find a new geometric design providing better aerodynamic performances like the TE (Truncated Ellipse) and the TEM (Truncated Ellipse Modified) in low Reynolds number for 2D and 3D simulations.
    Different geometric parameters influence the performances as the thickness and the chord length.
    The final CFD results give us the TEM which follows the Kammtail principles. This design shows a lower drag coefficient than TE or NACA. At low yaw angles (≤ 10 degrees), the TEM has better performances and is acting as a bluff body and thus the flow separation is delayed. At higher yaw angles (>10 degrees), the aerodynamic drag coefficient combined with an extremely high aerodynamic lift coefficient gives a much lower drag coefficient along the chord direction. This high aerodynamic lift is given by the separation bubble found on the TEM at a higher yaw angle.
    About 3D simulations, at low yaw angle, the cycling drag coefficient is close to the 2D simulations. But at higher yaw angle, the performances are damaged due to the lift-induced drag. And these results are confirmed by experiences (dye injection, PIV).

    ABSTRACT 1 ACKNOWLEDGEMENTS 3 CONTENTS 4 LIST OF TABLES 8 LIST OF FIGURES 10 LIST OF SYMBOLS 16 CHAPTER I : INTRODUCTION 18 I.1 General Introduction 18 I.2 Previous and related studies 20 I.2.1 About cycling aerodynamics in general 20 I.2.2 About cross sectional foils 23 I.3 Software 27 I.3.1 CATIA V5 27 I.3.2 Pointwise 28 I.3.3 ANSYS Fluent 14 29 I.3.4 Photron Fastcam viewer 30 I.3.5 PIV view 2C/3C 31 I.4 Cycling referential and UCI regulations 31 I.4.1 Cycling referential 31 I.4.2 UCI regulation 33 I.5 Flow parameters and the convergence parameters 34 I.5.1 Flow parameters 34 I.5.2 Convergence parameters 40 CHAPTER II : DESCRIPTION OF THE MODELS 43 II.1 Truncated Ellipse (TE) 43 II.2 Double Ellipse 43 II.2.1 Tangent Ellipses 44 II.2.2 Double ellipses: total length fixed 44 II.2.3 Ellipses crosses in ¼ or ¾ of diameter 46 II.2.4 Double ellipses: distance calculated 47 II.3 Truncated Ellipse Modified (TEM) 47 CHAPTER III : ABOUT MESHING ISSUES 49 III.1 What is a mesh? 49 III.2 Cell and mesh types 50 III.2.1 Cell types 50 III.2.1 Mesh types 51 III.3 Mesh quality criteria 53 III.3.1 Aspect ratio criteria 53 III.3.2 Skewness 54 III.4 Mesh used 56 CHAPTER IV : STUDIES OF DOUBLE ELLIPSES 60 CHAPTER V : GEOMETRIC PARAMETERS CASES 63 V.1 Aspect ratio 63 V.1.1 Length modified 63 V.1.2 Thickness modified 64 V.2 Corners of trailing edge 65 V.3 Method validation with water channel experiment 66 V.4 Method validation with P.I.V. experiment 67 CHAPTER VI : GEOMETRIC PARAMETERS RESULTS 68 VI.1 Different models comparison 68 VI.2 Aspect ratio 72 VI.2.1 Chord length modified 73 VI.2.2 Thickness modified 76 VI.3 Corners of trailing edge 78 CHAPTER VII : FLOW PARAMETERS RESULTS 82 VII.1 0 degree of yaw angle 82 VII.2 5 degree of yaw angle 84 VII.3 10 degree of yaw angle 86 VII.4 15 degree of yaw angle 89 VII.5 17 degree of yaw angle 92 CHAPTER VIII : 3D 96 VIII.1 The model 96 VIII.2 Simulation results 97 CHAPTER IX : WATER CHANNEL EXPERIMENT 99 IX.1 The system 99 IX.2 The dye injection and painting experiment 101 IX.2.1 0 degree of yaw angle 101 IX.2.2 10 degree of yaw angle 103 IX.2.3 15 degree of yaw angle 106 CHAPTER X : P.I.V. EXPERIMENT 112 X.1 Presentation of the P.I.V. method 112 X.2 The P.I.V. experiment 113 CHAPTER XI : CONCLUSION AND RECOMMENDATION 120 XI.1 Conclusion 120 XI.2 Recommendation for future work 121 REFERENCES 122

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