臺灣博碩士論文加值系統

本文以風洞測量及油流視察技術，探討不同厚度、曲率之翼剖面於低雷諾樹下三維機翼遲滯現象的參數影響，由實驗的結果可以發現到，當厚度和曲率增加時，所產生的遲滯現象也越大；在雷諾數方面，從實驗結果我們發現到，隨著雷諾數的增加(40000~100000)，遲滯現象的大小並不線性的變化，再雷諾數較低的時候，遲滯現象的大小會先隨著雷諾數的增加而變大，在經過一個特定雷諾數後，遲滯現象的大小怎會開始隨著雷諾數的增加而縮小。
在油流視察探討上，藉由遲滯現象發生攻角範圍內與範圍外流態之對比，發現遲滯現象發生之時同一攻角存在兩個不同流態，以何種流態出現流場，取決於機翼進入新攻角時，一開始所感受之邊界層擾動型態。
另外於翼面加裝干擾片，探討翼面幾何擾動對遲滯現象之影響，發現當干擾片黏貼在翼弦部分時，當干擾片厚度為邊界層厚度一半時，如干擾片安置在距離翼前緣5mm處，會造成一個層流失速的現象，也因此造成遲滯現象的消失。根據視流的結果可以看到，在未裝置干擾片的狀況下，分離泡在低攻角下就會產生，並隨著攻角的增加而變小並往翼前緣方向移動，在遲滯現象產生後，增加攻角(未失速)和減少攻角(失速)的流場，會有很大的不同，未失速時可以發現到流場已經開始趨向不穩定，而在失速後也可看到失速的範圍組要集中在翼根處，翼尖處因受到翼尖渦流的影響，還是有部分分離泡產生；在干擾片安裝後，發現干擾片會固定住分離泡的大小和位置，等到失速攻角後，會在翼前緣造成流場的層流分離，以至於失速的產生，並使遲滯現象消失。

The transition mechanism for the hysteresis phenomenon of 3-D wings at low Reynolds number range is experimentally studies in a low speed wind tunnel. The aerodynamic force measurements and oil flow visualization of the 3-D wings are carefully conducted at various Reynolds number between 4x104< Re <10x104 with the influence parameters of thickness and camber ratios of the wings. Results indicate that the hysteresis loop of the aerodynamic lift curve with AOA will be apparently arised and gradually enlarged as the thickness and camber ratio of the wings increase. In addition, this hysteresis loop also keeps increasing with the increase of the Reynolds number operated. However, until reaching a specific Reynolds number of shrinking, the loop will be shrunk, in stead, as the Reynolds number increases.
The result from the oil flow visualized has approved the existence of the hysteresis loop in the operatig Reynolds numbers. It further confirms that, during increasing and decreasing AOA of the wings, the hysteresis loop of the aerodynamic loop will be determined by the boundary layer status of the floe where the flow is either separated in the leading edge or already developed to surface vortex separation which is strongly affected by the trailing vortices
In order to realize the effects of boundary layer perturbation on hysteresis phenomenon, the mechanical trips are placed at different span and chordwise locations to measure the aerodynamics. If the trip is attached on the spanwise direction, the hysteresis loop will disappear. If the trip is on chordwise direction while the location is 5mm from leading edge, the laminar stall still exists, and the hysteresis phenomenon will disappear though.

ABSTRACT IN CHINESE......................................................... I
ABSTRACT IN ENGLISH......................................................... II
ACKNOWLEDGEMENT............................................................. III
CONTENTS.....................................................................IV
LIST OF TABLE................................................................VI
LIST OF FIGURE...............................................................VII
APPENDIX.....................................................................IX
NOMENCLATURE.................................................................X

Chapter　　　　　　　　　　　　　　 page

I. INTRODUCTION............................................................1
1-1 Aerodynamic Characteristics at Low Re..................................2
1-1-1 General Concept....................................................................2
1-1-2 Laminar Separation Bubbles...........................................3
1-1-3 Hysteresis Phenomena.................................................4
1-2 Motivation and Objectives..............................................9

II. EXPERIMENT APPARATUS..................................................10
2-1 Wing Tunnel ..........................................................10
2-2 Experiment Apparatus .................................................10
2-3 Wing Model and Supporting Device......................................11
2-4 Components of Flow Visualization......................................12
2-5 Uncertainty Analysis................................................. 12

III. EXPERIMENT RESULTS AND DISCUSSION................................... 14
3-1 Studies on Low Reynolds Number Aerodynamic Properties.................14
3-1-1 Thickness and Camber Effect.........................................14
3-1-2 Reynolds Number effect..............................................15
3-2 Characteristics of NACA0015...........................................16
3-3 Trip Effect on the Transition Behaviors of Airfoils...................17
3-3-1Changing Trip Locations in Spanwise Direction....................... 17
3-3-2Changing Trip Locations in chordwise Direction...................... 18
3-4 Qualitative Models for Hysteresis Phenomenon......................... 18

IV. CONCLUSION........................................................... 25

REFERENCE................................................................ 27

APPENFIX..................................................................64
A-1: Experiment Results: pure wing........................................64
A-2: Experiment Results: Changing Trip Locations in
Chordwise Direction..................................................71
A-3: Experiment Results: Changing Trip Locations in
Spanwise Direction...................................................75
VITA......................................................................83
PUBLICATION LISTS.........................................................84

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