飛機設計的好壞來自於安全和效率，由於資源的損耗和短缺，傳統飛機已不符合和現代的需求。隨著科技的進步，一種革命性的發展'翼身合一飛機'，擁有較好的升阻比和減低噪音，能夠減少對燃油的消耗和環境的污染。由於溫室效應的影響，極端惡劣天氣變得相當頻繁，對於飛機起飛降落會造成相當大的影響。在這篇論文主要考慮的天氣因素是側風和大雨。在開始運用CFD模擬側風和大雨對翼身合一飛機的影響之前，先驗證M6-wing確保我們的模擬是具有可信度的。側風主要會影響飛機橫向和航向是否穩定，如果滿足穩定條件，飛機經過本身自己的調整就會回到本身的位置，如果不穩定，則會造成偏轉、翻滾，會對飛機造成很重大的影響。這篇論文假設了10m/s、20m/s和30m/s的側風速度。大雨主要會影響飛機的升力係數和阻力係數。這篇論文運用了Fluent DPM的機制模擬了大雨的強度LWC=25g/m3 和LWC=39g/m3對翼身合一飛機的影響。本篇論文主要運用Pro/E建立翼身合一飛機外型，並運用Fluent模擬側風和大雨的影響。本論文希望對未來飛機設計，或飛行安全考量都更有助益。

The goal of aircraft design is to achieve safe and efficient flight. In the world of civilian air transport, efficient, economically attractive configurations are urgently needed. As for civilian commercial aircrafts, studies have shown remarkable performance improvements for the Blended Wing Body (BWB) over conventional subsonic transport. On the other hand, global warming has led to extreme weather around the world frequently, if aircraft taking-off and landing will unavoidably meet with the strong crosswind or/and heavy rain, then aircraft designer must put these severe werather influence into considerations in the conceptual design phase phase. One way to investigate the BWB airplane performance degradation is through CFD calculation. 
   The detrimental crosswind effects to Blended Wing Bod aircraft longitudinal, lateral and directional stability situation will be presented in this study. The speed of crosswinds considered here are 10m/s, 20m/s and 30m/s. Comparing with Boeing 747-100, no matter BWB is static stable or not, its stability derivative values under crosswind are always smaller than Boeing 747-100, representing the intrinsic nature of BWB static unstable tendency. Also, the heavy rain influence of different rain rates is that the lift coefficient is decreased and drag coefficient is increased at all different angle of attack spectrum. Comparing the different rain rates, liquid water content 39 g/m3 is more influential than 25 g/m3, with maximum reduction of lift coefficient is at angle of attack 0 degree and maximum increase of drag coefficient is at angle of attack 6 degree.
   In this study, Fluent is used as a simulation tool, the structure grid is chosen and generated by Gambit, and the standard M6 wing is first validated to ensure this simulation process is correct. This study hope to recognize and comprehend the basic aerodynamic performance for Blended Wind Body aircraft under severe weather situation, and the information gained here will be helpful for future transport aircraft designers.

Contents
Abstract	III
Contents	V
List of Figures	VII
List of Tables	XI
Nomenclature	XIII
Chapter 1 Introduction	1
Chapter 2 Reference Research	5
2-1 Blended Wing Body Aerodynamics	10
2-2 Static Stability	12
2-3 Heavy Rain on Airfoil	17
Chapter 3 Numerical Modeling	24
3-1 Geometry Model Construction	24
3-2 Grid Generation	28
3.3 Navier-Stokes Equations	33
3-4 Turbulence Model	34
3-5 Crosswind	37
3-6 Discrete Phase Model	38
3-7 Verification	40
Chapter 4 Results and Discussion	46
4-1 Coefficient of Lift, Drag and Longitudinal Stability	46
4-2 Lateral and Directional Stability with Crosswind	53
4-3 Heavy Rain Condition	63
Chapter 5 Conclusions	75
References	77



List of Figures
Figure 2-1: G.38 [3] ............................................................ 5
Figure 2-2: AW52 [4] .......................................................... 6
Figure 2-3: YB49 [5] ........................................................... 7
Figure 2-4: B-2 Spirit [6] .................................................... 8
Figure 2-5: The Boeing BWB-450 baseline [7] ...................... 9
Figure 2-6: Coefficient of lift thickness to chord ratio over the wing span. [7] ................................................... 11
Figure 2-7: The six-degree-of-freedom for a rigid airplane [13] ........................................................................ 13
Figure 2-8: The pitching moment of airplane [15] ............... 15
Figure 2-9: The rolling moment of airplane [15] ................. 16
Figure 2-10: The yawing moment of airplane [15] ............... 17
Figure 2-11 Characteristics of four surface water flow regions:..........................1. droplet-impact region; 2. film-convection region; 3.rivulet-formation region; and 4. droplet-convection region [22]. 23
Figure 3-1 Blended Wing Body geometry model [12] ........... 24
Figure 3-2 Blended Wing Body geometry model in 3D ......... 25
Figure 3-3 The airfoil section profile at y=0.0, 6.0 and y=0.0, -6m .................................................................. 25
Figure 3-4 The airfoil section profile at y=10.0, 13.0 m and y=-10.0, -13.0m ................................................ 26
Figure 3-5 The airfoil section profile y=17.5, 23.5, 38.75 m and y=-17.5,-23.5,-38.75m ....................................... 26
Figure 3-6 Twist angle distribution .................................... 27
Figure 3-7 Far mesh of the Blended Wing Body .................. 29
Figure 3-8 Near mesh of the Blended Wing Body ................ 30
Figure 3-9 Multi-block for Blended Wing Body .................. 30
Figure 3-10 Near structure mesh of the Blended Wing Body . 31
Figure 3-11 The Y plus at cruise condition .......................... 32
Figure 3-12 The Y plus with free stream velocity 49.4774 m/s ........................................................................ 32
Figure 3-13 Near structure mesh of the Blended Wing Body . 41
Figure 3-14 The Y plus of M6 wing(x/c=0.4) ...................... 42
Figure 3-15 Pressure coefficients at section y/b=0.2 ............ 42
Figure 3-16Pressure coefficients at section y/b=0.4 ............. 43
Figure 3-17 Pressure coefficients at section y/b=0.65 .......... 43
Figure 3-18 Pressure coefficients at section y/b=0.8 ............ 44
Figure 3-19 Pressure coefficients at section y/b=0.9 ............ 44
Figure 3-20 Pressure coefficients at section y/b=0.95 .......... 45
Figure 3-21 Pressure coefficients at section y/b=0.99 .......... 45
Figure 4-1 The coefficient of lift with free stream velocity 49.4774m. ......................................................... 48
49.4774m. ......................................................... 49
Figure 4-3 The CL vs. CD with free stream velocity 49.4774m ........................................................................ 49
Figure 4-4 Compare with Qin pressure drag and skin fraction drag. ................................................................. 51
Figure 4-5 The coefficient of moment with Mach number 0.85 free stream velocity 49.4774m. .......................... 53
Figure 4-6 Compare Cl and Cn with invicid and viscous case at AOA=00 ............................................................ 55
Figure 4-7 Compare Cl and Cn with invicid and viscous case at AOA=10 ............................................................ 56
Figure 4-8 The Cl with different crosswind speed in different angle of attack. ................................................. 61
Figure 4-9 The Clβ variation in different angle of attack. .... 62
Figure 4-10 The Cn with different crosswind speed in different angle of attack. ................................................. 63
Figure 4-11 The Cnβ variation in different angle of attack. ... 63
Figure 4-12 The comparing coefficient of lift in two rain rates. ........................................................................ 66
Figure 4-13 The comparing coefficient of drag in two rain rates. ........................................................................ 66
LWC=39g/m3. ................................................... 67
Figure 4-16 z/b=41.18% Cp contour at LWC=0g/m3 and LWC=39g/m3 .................................................... 67
Figure 4-17 z/b=91.18% Cp contour at LWC=0g/m3. ........... 68
Figure 4-18 The comparing coefficient of lift decreased ratio in tow rain rates. ................................................... 70
Figure 4-19 The comparing coefficient of drag increased ratio in two rain rates. ................................................... 70
Figure 4-20 The comparing lift to drag ratio in two rain rates. ........................................................................ 72
Figure 4-21 The bar chart comparing lift to drag ratio in two rain rates ................................................................. 72
Figure 4-21 The particles impact to Blended Wing Body by Fluent. .............................................................. 74



List of Tables
Table 2-1 A performance comparison of the BWB-450 with the A380-700 for 480 passengers and 8,700 nm range [8] ........................................................................ 10
Table 3-1 ONERA M6 wing geometry [25]. ......................... 40
Table 4-1 The coefficient of lift, drag and moment at 0.85 Mach number. ............................................................ 46
Table 4-2 The lift, drag and moment coefficient at free stream velocity 49.4774 m/s. ........................................ 47
Table 4-4 Cmα variation in the simulation at Mach Number 0.85. ........................................................................ 51
Table 4-5 Cmα variation in the simulationat at free stream velocity 49.4774 m/s. ........................................ 52
Table 4-8 The Cl and Cn variation with different crosswind speed at angle of attack 00. ................................ 56
Table 4-9 The Cl and Cn variation with different crosswind speed at angle of attack 10. ................................ 56
Table 4-10 The Cl and Cn variation with different crosswind speed at angle of attack 20. ................................ 57
Table 4-11 The Cl and Cn variation with different crosswind speed at angle of attack 30. ................................ 57
Table 4-12 The Cl and Cn variation with different crosswind speed at angle of attack 40. ................................ 58
Table 4-13 The Cl and Cn variation with different crosswind speed at angle of attack 60. ................................ 58
Table 4-14 The Cl and Cn variation with different crosswind speed at angle of attack 80. ................................ 59
Table 4-15 The Cl and Cn variation with different crosswind speed at angle of attack 100. ............................... 59
Table 4-16 The Cl and Cn variation with different crosswind speed at angle of attack 120. ............................... 60
Table 4-17 The CL and CD variation with at liquid water content 25g/m3. ................................................. 64
Table 4-18 The CL and CD variation with at liquid water content 39g/m3. ................................................. 64
Table 4-21 The CL decreased and CD increased variation with at liquid water content 25g/m3 and 39g/m3. ............. 69
Table 4-22The lift to drag decreased variation with at liquid water content 25g/m3 and 39g/m3 ....................... 71
Table 5-1 Boeing 747-100 and Blended Wing Body static stability data. .................................................... 75

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