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研究生： 林黛安
Diane, Scoboria
論文名稱： 淚滴型圓柱厚度與層流分離泡現象關係之實驗研究
Experimental investigation of laminar separation bubbles on a series of teardrop cylinders with increasing thickness
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： 2025
畢業學年度： 113
語文別： 英文
論文頁數： 142
中文關鍵詞： 層流分離泡 、圓柱厚度 、淚滴形圓柱 、阻力係數 、臨界狀態
外文關鍵詞： Laminar separation bubble, cylinder thickness, teardrop cylinder, drag coefficient, critical regime
相關次數： 點閱：33  下載：5 
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    • 本研究探討淚滴型圓柱厚度對層流分離泡(LSB)形成的影響，透過表面壓力測量、油膜可視化、力平衡實驗以及CFD模擬進行分析。研究中針對三種厚度比分別為0.2、0.3及0.4的淚滴形圓柱，在雷諾數範圍2.8x104 ≤ Re ≤ 1.5x105和攻角0°至10°(包含0.5°、1°、2.5°及5°)的條件下，進行臨界狀態(Critical regime)的流場現象探討。結果顯示，隨著圓柱厚度增加，壓力係數的均方根值(CpRMS)會放大，LSB在較低攻角時更容易破裂，對於流場現象有顯著的改變。另一方面，本研究也發現，與NACA翼型和較薄的淚滴模型相比，傳統的淚滴形會在迎風側產生層流分離泡（LSB），因此其升力、阻力和臨界雷諾數特性等表現都與其他模型不同。另外，本研究還分析了非定常流場特性、渦街的斯特勞哈爾數、翼展方向上的LSB分布、Trip strip的效果，以及基於 k-kl-ω紊流模型的CFD模擬結果，這些發現進一步深化了對臨界狀態下LSB的理解。

    This study investigates the influence of teardrop cylinder thickness on laminar separation bubble (LSB) formation using surface pressure measurements, oil film visualization, force balance, and CFD. Three teardrop cylinders with thickness ratios of 0.2, 0.3, and 0.4 are examined in the Reynolds number range 2.8x104 ≤ Re ≤ 1.5x105 and angles of attack 0°, 0.5°, 1°, 2.5°, 5°, and 10° with a focus on the critical regime. Increased cylinder thickness amplifies CpRMS, discourages LSB formation at lower angles of attack, and influences flow dynamics. The traditional teardrop geometry, compared to NACA airfoils and thinner teardrop models, exhibits a windward LSB, leading to atypical lift, drag, and critical Reynolds number characteristics. The study explores non-stationary features, vortex shedding Strouhal numbers, spanwise LSB formation, trip strips, and CFD simulations using the k-kl-ω turbulence model. These insights deepen the understanding of LSB dynamics in the critical regime.

    摘要 II SUMMARY III ACKNOWLEDGEMENTS IV TABLE OF CONTENTS V LIST OF TABLES VIII LIST OF FIGURES IX NOMENCLATURE XIX CHAPTER 1 INTRODUCTION 1 1.1 Background 1 1.2 Literature 2 CHAPTER 2 METHOD AND SETUP 9 2.1 LSB Regimes 9 2.2 Wind tunnel 11 2.3 Experimental parameters 11 2.4 Models 11 2.5 Characteristic length & width 13 2.6 Endplate setup 14 2.7 Free end condition setup 16 2.8 Angle of attack calibrator 16 2.9 Pressure measurements 17 2.10 Oil film visualization 19 2.11 Oil film visualization and surface pressure comparison 20 2.12 Accelerometer 20 2.13 FFT and spectrogram 20 2.14 Cross hot-wire 21 2.15 Intermittency frequency noise analysis 21 2.16 Strouhal number noise analysis 22 2.17 Force balance 22 2.18 Trip Strip 22 2.19 CFD 23 2.20 Definitions 26 CHAPTER 3 RESULTS AND DISCUSSION 28 3.1 LSB regime overview 28 3.2 Ranges of the critical regime (T20, T30, and T40 at AOA = 0°) 30 3.3 Ranges of the critical regime (C and Cw) 31 3.4 Physical findings in LSB pressure measurements 32 3.4.1 T20 32 3.4.2 T30 35 3.4.3 T40 37 3.5 Characteristics due to small AOA changes (0°, 0.5°, 1°) 40 3.6 Cd, drag crisis, and base pressure coefficient 43 3.6.1 AOA = 0° 45 3.6.2 AOA = 2.5° 46 3.6.3 AOA = 5° 46 3.6.4 AOA=10° 47 3.6.5 Windward and leeward LSB comparison 47 3.6.6 Cd in literature 49 3.7 Spatial and temporal LSB distribution 51 3.7.1 Temporal LSB formation 51 3.7.2 Spanwise LSB formation: AOA = 0° 52 3.7.3 Spanwise LSB formation: T20 critical model width at AOA = 0° 56 3.8 Non-stationary factors 59 3.8.1 Examples: LSB intermittency 59 3.8.1.1 Examples 1-2: Calm and vibrant LSB 59 3.8.1.2 Example 3: Sudden critical regime 65 3.8.1.3 Example 4: Low intermittency critical regime 66 3.8.2 CpRMS 68 3.8.3 Vortex shedding: T20, T30, and T40 70 3.8.4 Vortex shedding: Spectrogram 72 3.8.5 Strouhal number: T40 endplate vs T40 free end condition 77 3.8.6 Kelvin-Helmholtz instabilities 78 3.9 Negative lift coefficient (T40) 78 3.10 Hysteresis 82 3.11 CFD 84 3.11.1 CFD validating experiments 84 3.11.2 CFD with conducive LSB conditions 87 3.11.3 CFD and flow separation 89 3.11.4 CFD and turbulent reattachment 91 3.11.5 CFD limitations and literature 94 3.12 Trip Strip 95 3.12.1 Trip strip oil film visualization 95 3.12.2 Trip strip separation location 97 3.13 Bicycle support application 100 CHAPTER 4 CONCLUSIONS AND SUGGESTIONS 101 REFERENCES 103 APPENDIX A. PRESSURE TAP LOCATIONS 109 APPENDIX B. LSB REGIMES AND LOCATIONS 110 APPENDIX C. STROUHAL NUMBER FREQUENCY IDENTIFICATION 114 APPENDIX D. INTERMITTENCY EXAMPLES AND FREQUENCY ANALYSIS 116

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