臺灣博碩士論文加值系統

中文摘要
本研究探討有限長機翼後緣加裝振動片激擾對於尾流的結構以及發展情形之抑制。實驗使用NACA0012的有限長矩形翼作為基本模型，藉由翼後緣加裝自由振動片以及由馬達控制上下擺動頻率(5Hz)之振動片對尾流作激擾，探討此類激擾對尾流結構及發展情形之影響及改變。在實驗過程中風洞的風速為20m/s，翼弦雷諾數 ，攻角維持於12度。藉由五孔皮託管量測三維速度方向後，對流場資料作分析。流場資料顯示：於翼後緣加裝自由振動片激擾，對於尾流結構及發展情形的抑制達到效果。由馬達控制上下擺動頻率(5Hz)之振動片激擾，對於尾流結構及發展情形的抑制可分成兩個區域：尾流成長區以及潰散區。在尾流成長區中，渦流強度以及側向速度的成長甚至有超越基本翼型尾流發展的趨勢。在潰散區， 發現渦流強度及側向速度相較於基本翼型和加裝自由振動片激擾而言，有明顯的衰退趨勢。實驗所得到的結果顯示：翼後緣固定頻率(5Hz)振動片激擾的確對於尾流結構及發展情形產生更明顯有效的抑制作用。

ABSTRACT
This thesis studies the suppression of the wake structure and its development behind a finite wing under flapping excitation at the trailing edge of the wing. The basic model of the finite wing in the experiments is a rectangular wing with NACA0012 airfoil. By means of both free flaping and fixed frequency flapping excitations, the suppression of the wake structure and development in the trailing vortices are investigated in details. The freestream velocity is kept at 20m/s with the corresponding Reynolds number of based on the wing chord, and the angle of attack (AOA) of 12 degrees throughout the experiments is operated. Flowfield data would be analyzed, after all three dimensional flow fields in streamwise (U), transverse (V), and spanwise (W) directional are measured by using a five-hole pitot tube. The experimental data indicates that the suppression of the wake structure is apparently under the free flapping excitation. Under 5Hz frequency flapping excitation, the downstream wake flow development can be divided into two ranges: wake-developing range and wake-decay range. Within the wake-developing range, the growth of the vorticity strength and the transverse velocity tends to overtake the natural wake flow without excitation. Within the wake-decay range, it was found that the vorticity strength and transverse velocity tend to decrease more than the other cases. The experimental result has also proved that the 5Hz frequency flapping excitation case is more effective to suppress the wake flow structure and its development of the trailing vortices behind the finite wing model.

中文摘要........................................................Ⅰ
ABSTRACT..................................................Ⅱ
CONTENTS..................................................Ⅳ
LIST OF TABLES....................................................Ⅵ
LIST OF FIGURES...................................................Ⅶ
NOMENCLATURE..............................................ⅩⅤ
CHAPTER
Ⅰ INTORDUCTION……………………………………………………1
1.1 Preface………………………………………………………………………....1
1.2 Literature Survey.……………………………………………………………...3
1.3 Motivation and Objectives...…………………………………………………...6
Ⅱ EXPERIMENTAL FACILITY………..…………………………….…….8
2.1 Wind Tunnel……………………………………………………………………8
2.2 Experimental Model……………………………………………………………8
2.3 Measurement System……………………………………………………….…..9
2.3.1 Calibration of Five-Hole Pitot Tube……………………………….….…..9
2.4 Traversing Mechanism…………………………………………………………..13
2.5 Data Acquisition System………………………………………………..…….14
Ⅲ EXPERIMENTAL PROCEDURES AND PRINCIPLES……….….15
ABSTRACT
C3.1.1 Test Conditions………………………………………………………….15
3.1.2 Measuring Range…………………………………...……………………15
3.1.3 Nondimensionalize Scale………………………………………………..16
3.1.4 Experiment Setup………………………………………………………..16
3.2 Experimental Principles……………………………………………………….17
3.2.1 Scale of Plane Wake…………………………………..…………………17
3.2.2 Scale of Vortex Radius…………………………………………………..17
3-2-3 Streamwise Vorticity………………………...…………………..………18
Ⅳ RESULTS AND DISCUSSIONS…………….……………………………..19
4.1 Basic Flow Structure………………………………………………………….19
4.1.1 Flow Development of Mean Velocity Along Downstream…….………..19
4.1.2 Mean Crossflow Velocity Vectors Along Downstream……………….…22
4.1.3 Vorticity Along Downstream……………...………………………….….23
4.2 Wake Behavior in Flapping Excitation………………………….…………….23
Ⅴ CONCLUSIONS AND SUGGESTIONS………………………………..27
5.1 Conclusions……………………………………………………………………27
5.2 Suggestions for Further Study…………………………………………………28
REFERENCES…………………………………………………………………….29

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