現今全球溫室效應影響和極端天氣現象越來越嚴重。在世界各地裡，對人類生命傷亡及財產損失造成嚴重的迫害。全球溫室效應的影響幾乎無所不在且更加頻繁。目前在極端氣象下，直升機已經成為全球救援空勤單位中最廣泛利用的飛行器。由於這個原因，了解和改善在惡劣天氣如陣風和大雨的條件下，直升機的空氣動力學分析是本研究的重點。模擬直升機懸空時，加入軸向(向上、向下)及側向均勻風或正弦陣風和大雨。使用研究團隊中已經開發模擬的雨滴撞擊二相流方法，然後嵌入直升機旋轉葉片表面粗糙度的影響。結果顯示，發現複雜的非線性效應影響著升力和阻力，但似乎垂直正弦陣風引起升力最大影響；而大雨是相較明顯影響阻力。雖然目前的工作只集中於對稱翼型和缺乏大雨實驗數據進行比較，但相信我們的研究結果還是證明，惡劣氣象在直升機上，定性和定量的不利影響。強烈建議，在惡劣氣象情況下，每一位飛行員應該在這項工作中獲得的此訊息，並接受廣泛的訓練，但還認為直升機在大雨情況下應該進行更多的實驗，以驗證我們的結果。

Nowadays the extreme weather phenomenon have becoming more and more severe, causing detrimental effects on human life and property damage all over the world. Almost everywhere, global warming effects impact stronger winds and heavy rain upon us more often. Currently, helicopter has widespread utilization in air rescue mission during disaster situation under extreme weather situations. For this reason the understanding and improvement of helicopter operation under severe weather such as gusty wind and heavy rain condition are the focal points of this research. A numerical simulation tool has been developed and validated for hovering helicopter blades, with the addition of uniform wind, sinusoidal gusty wind, and heavy rain surrounding that blow from upward, downward, and cross directions. For rain droplet impingement simulation, a two-phase flow approach has first been developed and then the surface roughness effects are also included for helicopter rotating blades. Results show a complicated nonlinear effect on hovering helicopter lift and drag forces, but it seems the vertical sinusoidal gust wind induces largest impact on lift, whilst heavy rain is more influential to drag. Although current work is only concentrated on symmetric airfoil and lacking heavy rain experimental data to compare with, it is believed that our results still show the severe weather detrimental effects on helicopter, both qualitatively and quantitatively. While it is highly recommended that every helicopter pilot should be aware of the information gained in this work and accepts extensive training in severe weather situations, it is felt that more experiment should be conducted for helicopter in gust and heavy rain conditions in the future.

Contents
ABSTRACT:	III
CONTENTS	V
LIST OF FIGURES	VII
LIST OF TABLES	X
LIST OF SYMBOLS	XI
CHAPTER 1	INTRODUCTION	1
CHAPTER 2	RESEARCH BACKGROUND	5
2.1.	HELICOPTER ROTOR AIRFOIL	5
2.2.	GUSTY WIND	12
2.3.	HEAVY RAIN EFFECT	14
CHAPTER 3	NUMERICAL MODELING	20
3.1.	OVERVIEW	20
3.2.	GEOMETRY MODEL CONSTRUCTION	21
3.3.	GRID GENERATION	23
3.4.	GOVERNING EQUATIONS	25
3.5.	TURBULENCE MODELING	26
3.6.	MULTIPLE REFERENCE FRAME (MRF) CAPABILITY	27
3.7.	DISCRETE PHASE MODEL (DPM) CAPABILITY	29
3.8.	FLOW SOLVER	32
3.9.	VERIFICATION AND MESH INDEPENDENCE	33
CHAPTER 4	RESULTS AND DISCUSSION	38
4.1.	GUSTY WIND EFFECTS ON HELICOPTER BLADE	39
4.2.	WIND AND HEAVY RAIN EFFECTS ON HELICOPTER BLADE	55
4.3.	SEVERE WEATHER EFFECTS ON MICRO ROTARY WING BLADE	63
CHAPTER 5	CONCLUSIONS	65
REFERENCES	68
APPENDIX	72

List of Figures
FIGURE 2-1 HOVERING FLIGHT DISTRIBUTION OF INCIDENT VELOCITY NORMAL TO THE LEADING EDGE OF ROTOR BLADE. [1] ...................................................................... 5
FIGURE 2-2: THE NASA MODEL AND EXPERIMENTS SET-UP. [5] ...................................... 7
FIGURE 2-3: THE UH-1H HELICOPTER PROFILE. ........................................................... 12
FIGURE 3-1 THE MODEL OF HELICOPTER BLADES. ......................................................... 22
FIGURE 3-2 MODEL OF ALL COMPUTATIONAL ZONES. .................................................... 22
FIGURE 3-3 THE MESH OF ALL COMPUTATIONAL ZONES. (2.2 MILLION CELLS TYPE) ...... 23
FIGURE 3-4 THE MESH OF ROTATIONAL PART COMPUTATIONAL ZONE. (2.2 MILLION CELLS TYPE) .................................................................................................................... 24
FIGURE 3-5 THE NEAR MESH OF THE ROTOR BLADES. (2.2 MILLION CELLS TYPE) ........ 25
FIGURE 3-6 THE SOLUTION FLOW CHART OF THE SEGREGATED ALGORITHM SOLVER. .... 33
FIGURE 3-7 THE PRESSURE COEFFICIENT FOR 2.2M, 3.6M AND 5.1M CELLS GRID INDEPENDENT, AND COMPARE WITH NASA EXPERIMENT [5] IN R/R=0.5. .............. 35
FIGURE 3-8 THE PRESSURE COEFFICIENT FOR 2.2M, 3.6M AND 5.1M CELLS GRID INDEPENDENT, AND COMPARE WITH NASA EXPERIMENT [5] IN R/R=0.68. ............ 35
FIGURE 3-9 THE PRESSURE COEFFICIENT FOR 2.2M, 3.6M AND 5.1M CELLS GRID INDEPENDENT, AND COMPARE WITH NASA EXPERIMENT [5] IN R/R=0.8. .............. 36
FIGURE 3-10 THE PRESSURE COEFFICIENT FOR 2.2M, 3.6M AND 5.1M CELLS GRID INDEPENDENT, AND COMPARE WITH NASA EXPERIMENT [5] IN R/R=0.89. ............ 36
FIGURE 3-11 THE PRESSURE COEFFICIENT FOR 2.2M, 3.6M AND 5.1M CELLS GRID INDEPENDENT, AND COMPARE WITH NASA EXPERIMENT [5] IN R/R=0.96. ............ 37
FIGURE 4-1 THE SINUSOIDAL FUNCTION WIND FIELD. ................................................... 40
FIGURE 4-2 THE AIRFOIL PRESSURE COEFFICIENT CONTOURS AT R/R = 0.96 IN HOVER. . 42
FIGURE 4-3 THE AIRFOIL PRESSURE COEFFICIENT CONTOURS AT R/R = 0.96 IN 10 M/S UNIFORM WIND (CROSS). ....................................................................................... 42
FIGURE 4-4 THE AIRFOIL PRESSURE COEFFICIENT CONTOURS AT R/R = 0.96 IN 20 M/S UNIFORM WIND (CROSS). ....................................................................................... 42
FIGURE 4-5 THE AIRFOIL PRESSURE COEFFICIENT CONTOURS AT R/R = 0.96 IN 10 M/S SINUSOIDAL WIND (CROSS). ................................................................................... 42
FIGURE 4-6 THE AIRFOIL PRESSURE COEFFICIENT CONTOURS AT R/R = 0.96 IN 20 M/S SINUSOIDAL WIND (CROSS). ................................................................................... 42
FIGURE 4-7 THE AIRFOIL PRESSURE COEFFICIENT CONTOURS AT R/R = 0.96 IN 10 M/S UNIFORM WIND (UPWARD). .................................................................................... 42
FIGURE 4-8 THE AIRFOIL PRESSURE COEFFICIENT CONTOURS AT R/R = 0.96 IN 20 M/S UNIFORM WIND (UPWARD). .................................................................................... 43
FIGURE 4-9 THE AIRFOIL PRESSURE COEFFICIENT CONTOURS AT R/R = 0.96 IN 10 M/S
VIII
SINUSOIDAL WIND (UPWARD). ............................................................................... 43
FIGURE 4-10 THE AIRFOIL PRESSURE COEFFICIENT CONTOURS AT R/R = 0.96 IN 20 M/S SINUSOIDAL WIND (UPWARD). ............................................................................... 43
FIGURE 4-11 THE AIRFOIL PRESSURE COEFFICIENT CONTOURS AT R/R = 0.96 IN 10 M/S UNIFORM WIND (DOWNWARD). .............................................................................. 43
FIGURE 4-12 THE AIRFOIL PRESSURE COEFFICIENT CONTOURS AT R/R = 0.96 IN 20 M/S UNIFORM WIND (DOWNWARD). .............................................................................. 43
FIGURE 4-13 THE AIRFOIL PRESSURE COEFFICIENT CONTOURS AT R/R = 0.96 IN 10 M/S SINUSOIDAL WIND (DOWNWARD). .......................................................................... 43
FIGURE 4-14 THE AIRFOIL PRESSURE COEFFICIENT CONTOURS AT R/R = 0.96 IN 20 M/S SINUSOIDAL WIND (DOWNWARD). .......................................................................... 44
FIGURE 4-15 THE AIRFOIL VELOCITY (M/S) CONTOURS AT R/R = 0.96 IN HOVER. ........... 44
FIGURE 4-16 THE AIRFOIL VELOCITY (M/S) CONTOURS AT R/R = 0.96 IN 10 M/S UNIFORM WIND (CROSS). ...................................................................................................... 44
FIGURE 4-17 THE AIRFOIL VELOCITY (M/S) CONTOURS AT R/R = 0.96 IN 20 M/S UNIFORM WIND (CROSS). ...................................................................................................... 44
FIGURE 4-18 THE AIRFOIL VELOCITY (M/S) CONTOURS AT R/R = 0.96 IN 10 M/S SINUSOIDAL WIND (CROSS). ................................................................................... 44
FIGURE 4-19 THE AIRFOIL VELOCITY (M/S) CONTOURS AT R/R = 0.96 IN 20 M/S SINUSOIDAL WIND (CROSS). ................................................................................... 44
FIGURE 4-20 THE AIRFOIL VELOCITY (M/S) CONTOURS AT R/R = 0.96 IN 10 M/S UNIFORM WIND (UPWARD). ................................................................................................... 45
FIGURE 4-21 THE AIRFOIL VELOCITY (M/S) CONTOURS AT R/R = 0.96 IN 20 M/S UNIFORM WIND (UPWARD). ................................................................................................... 45
FIGURE 4-22 THE AIRFOIL VELOCITY (M/S) CONTOURS AT R/R = 0.96 IN 10 M/S SINUSOIDAL WIND (UPWARD). ............................................................................... 45
FIGURE 4-23 THE AIRFOIL VELOCITY (M/S) CONTOURS AT R/R = 0.96 IN 20 M/S SINUSOIDAL WIND (UPWARD). ............................................................................... 45
FIGURE 4-24 THE AIRFOIL VELOCITY (M/S) CONTOURS AT R/R = 0.96 IN 10 M/S UNIFORM WIND (DOWNWARD). ............................................................................................. 45
FIGURE 4-25 THE AIRFOIL VELOCITY (M/S) CONTOURS AT R/R = 0.96 IN 20 M/S UNIFORM WIND (DOWNWARD). ............................................................................................. 45
FIGURE 4-26 THE AIRFOIL VELOCITY (M/S) CONTOURS AT R/R = 0.96 IN 10 M/S SINUSOIDAL WIND (DOWNWARD). .......................................................................... 46
FIGURE 4-27 THE AIRFOIL VELOCITY (M/S) CONTOURS AT R/R = 0.96 IN 20 M/S SINUSOIDAL WIND (DOWNWARD). .......................................................................... 46
FIGURE 4-28 LIFT COEFICIENT VERSUS REVOLUTION CYCLES WITH 10 M/S SINUSOIDAL WIND. .................................................................................................................... 51
IX
FIGURE 4-29 LIFT COEFICIENT VERSUS REVOLUTION CYCLES WITH 20 M/S SINUSOIDAL WIND. .................................................................................................................... 51
FIGURE 4-30 DRAG COEFICIENT VERSUS REVOLUTION CYCLES WITH 10 M/S SINUSOIDAL WIND. .................................................................................................................... 52
FIGURE 4-31 DRAG COEFICIENT VERSUS REVOLUTION CYCLES WITH 20 M/S SINUSOIDAL WIND. .................................................................................................................... 52
FIGURE 4-32 THE AIRFOIL PRESSURE COEFFICIENT CONTOURS AT R/R = 0.5 IN HOVER. . 53
FIGURE 4-33 THE AIRFOIL PRESSURE COEFFICIENT CONTOURS AT R/R = 0.5 IN 20 M/S SINUSOIDAL WIND (DOWNWARD). .......................................................................... 53
FIGURE 4-34 THE AIRFOIL PRESSURE COEFFICIENT CONTOURS AT R/R = 0.68 IN HOVER.53
FIGURE 4-35 THE AIRFOIL PRESSURE COEFFICIENT CONTOURS AT R/R = 0.68 IN 20 M/S SINUSOIDAL WIND (DOWNWARD). .......................................................................... 53
FIGURE 4-36 THE AIRFOIL PRESSURE COEFFICIENT CONTOURS AT R/R = 0.8 IN HOVER. . 53
FIGURE 4-37 THE AIRFOIL PRESSURE COEFFICIENT CONTOURS AT R/R = 0.8 IN 20 M/S SINUSOIDAL WIND (DOWNWARD). .......................................................................... 53
FIGURE 4-38 THE AIRFOIL PRESSURE COEFFICIENT CONTOURS AT R/R = 0.89 IN HOVER.54
FIGURE 4-39 THE AIRFOIL PRESSURE COEFFICIENT CONTOURS AT R/R = 0.89 IN 20 M/S SINUSOIDAL WIND (DOWNWARD). .......................................................................... 54
FIGURE 4-40 THE AIRFOIL PRESSURE COEFFICIENT CONTOURS AT R/R = 0.96 IN HOVER.54
FIGURE 4-41 THE AIRFOIL PRESSURE COEFFICIENT CONTOURS AT R/R = 0.96 IN 20 M/S SINUSOIDAL WIND (DOWNWARD). .......................................................................... 54
FIGURE 4-42 LOCAL VIEW OF RAIN DROPLET IMPINGEMENT AND SIZE DISTRIBUTION NEAR BLADES. ................................................................................................................ 55

List of Tables
TABLE 2-1 COEFFICIENTS OF LOGARITHMIC ATMOSPHERIC BOUNDARY LAYER MODEL. [18] ....................................................................................................................... 14
TABLE 4-1 BLADE LIFT FORCE AND LIFT COEFFICIENT COMPARISON UNDER DIFFERENT WIND CONDITIONS. ................................................................................................ 48
TABLE 4-2 BLADE DRAG FORCE AND DRAG COEFFICIENT COMPARISON UNDER DIFFERENT WIND CONDITIONS. ................................................................................................ 48
TABLE 4-3 BLADE DRAG FORCE COMPONENTS UNDER DIFFERENT WIND CONDITIONS. .. 49
TABLE 4-4 SURFACE ROUGHNESS VALUES FOR DIFFERENT CASES. ................................. 56
TABLE 4-5 THE LIFT COEFFICIENT COMPARISON FOR DIFFERENT ROUGHNESS VALUES. .. 57
TABLE 4-6 THE DRAG COEFFICIENT COMPARISON FOR DIFFERENT ROUGHNESS VALUES.57
TABLE 4-7 BLADE LIFT FORCE AND LIFT COEFFICIENT COMPARISON UNDER DIFFERENT WIND AND HEAVY RAIN CONDITIONS. .................................................................... 58
TABLE 4-8 BLADE LIFT FORCE AND DIFFERENCE COMPARISON UNDER DIFFERENT WIND AND HEAVY RAIN CONDITIONS. .............................................................................. 59
TABLE 4-9 BLADE DRAG FORCE AND DIFFERENCE COMPARISON UNDER DIFFERENT WIND AND HEAVY RAIN CONDITIONS. .............................................................................. 61
TABLE 4-10: BLADE DRAG COEFFICIENT COMPONENT PERCENTAGE COMPARISON UNDER DIFFERENT WIND AND HEAVY RAIN CONDITIONS. ................................................... 62
TABLE 4-11 BLADE LIFT COEFFICIENT CHANGE RATIO COMPARISON OF DIFFERENT MODEL SCALE COMPONENT COMPARISON UNDER WIND OR HEAVY RAIN. ........................... 64
TABLE 4-12 BLADE DRAG COEFFICIENT CHANGE RATIO COMPARISON OF DIFFERENT MODEL SCALE COMPONENT COMPARISON UNDER WIND OR HEAVY RAIN. ............... 64

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