近年飛機製造公司為了減少航空器運作成本而相繼推出強調省油與效率的飛機，翼胴合一飛行器即為在材料及技術的改進和航機大型化之外的一種解決方案。然而此型飛行器整體構造與傳統構型大不相同以致於對其製造、飛行乃至其它性能諸元皆無法掌握，故此種飛行器的相關性能研究成為近年許多研究單位的研究項目。本論文參考並仿製NASA所研發之X-48翼胴合一飛行器，以現有之計算流體力學軟體Fluent在0.85馬赫的高空巡航條件下，對其三維流場進行計算，比較不同翼尖裝置對其性能之影響。本論文所研究比較之翼尖裝置有一般常見之Winglet及一種較新穎的C-wing構型，此外本研究還針對另一翼胴合一飛行器研究論文所建立之飛機外形，進行計算並且互相比較。最後，本論文並對仿製的X-48外型進行最佳化計算及改進。挑選兩個飛機幾何參數並搭配使用CAD軟體、網格生程軟體、流場解算軟體以及自行寫作之程式碼，以期能改善模仿外形的表面流場、更動震波的位置及減少震波的強度，最終對飛行的效率提升了可觀的幅度。本研究結果可提供航空設計者對於航空飛機設計上靈感的啟發、增加設計工具的選用彈性、以及對於新型航空器的初步性能認識。在計算工具上更探討結構網格與非結構網格的優劣利弊和其對計算結果的影響差異，對於C-wing構型的利弊得失，也透過實際模型的預測，提供予飛機設計者作為重要的參考。

Aircraft manufacture companies have introduced new aircrafts with high fuel-efficiency to reduce the operation cost of flight vehicle in recent years; the blended-wing-body (BWB) aircraft is another solution besides the strategies of the improvement in structure/material and aircraft enlargement. But we cannot grasp the characteristics of manufacturing; flight efficiency, etc.; because the configuration of BWB is so different from the conventional one. So in recent years the related researches about this modern BWB aircraft become the topic of many research projects.
This thesis refers and imitates the aircraft of NASA’s X-48, and then simulates the three-dimensional flow field with the flight condition of Mach 0.85 cruise at the high altitude using the existing computational fluid dynamics (CFD) software named “Fluent”. And then it evaluates the efficiency of flight performance with different wingtip devices. The wingtip devices of this research are the general common winglet and the novel configuration of C-wing. In addition, this research also enlists the BWB geometry from another fellow student, while computing and comparing with these different configurations.
Another theme of this research is to do the optimisation study of the imitative X-48. We choose two values of twist angle parameter of the aircraft geometry, using software of CAD, grid generation, flow solver, and homemade programming codes. We expect that will improve the airflow on the surface of aircraft, move the position of shock wave, and weaken the strength of shock wave. Finally it increases the efficiency of aircraft for an apparent range. The result of this research will provide aircraft manufacture companies some inspiration of aircraft design, increased flexibility in the choice of design tools, and the preliminary understanding on flight performance of a new type of aircraft. We even investigate the pros and cons of structured and unstructured grid, and the difference in their simulated aerodynamic coefficients is quite large. One important finding of this study is that at least for our BWB configurations, the C-wing model does not seem to improve the cruise performance at all.

Contents
List of Tables ……………………………………………… VI
List of Figures …………………………………………… VII
Nomenclature …………………………………………… XI
Chapter 1 Introduction …………………………………… 1
Chapter 2 Literature Review ……………………………… 7
Chapter 3 Numerical Methods …………………………… 14
3.1 Model Construction ………………………………… 14
3.2 Grid Generation …………………………………… 22
3.3 Flow Field Solver …………………………………… 28
3.4 Optimisation ……………………………………… 31
3.5 Verification ………………………………………… 36
Chapter 4 Results and Discussion ………………………… 50
Chapter 5 Conclusions …………………………………… 60
References ………………………………………………… 62
Appendix ………………………………………………… 66
V
List of Tables
Table 3.1 Airfoil thickness (imitative X-48) ------------------------ 18
Table 3.2 Airfoil thickness (Yang BWB) --------------------------- 18
Table 3.3 Flight condition of M6 wing ------------------------------ 36
Table 3.4 Monitor section positions on M6 wing ---------------------- 38
Table 4.1 Data comparison of Yang BWB at AOA 2.0 degree ------ 53
Table 4.2 Data comparison of imitative X-48 at AOA 1.0 degree --- 53
Table 4.3 Twist angles ----------------------------------------------------- 58
Table 4.4 Optimisation result --------------------------------------------- 58
VI
List of Figures
Figure 1.1 DOC comparison ---------------------------------------- 01
Figure 1.2 Flying-wing to BWB ------------------------------------ 02
Figure 1.3 An other opinion ----------------------------------------- 02
Figure 1.4 Beam of stabilizer ---------------------------------------- 04
Figure 1.5 Airfoil and geometry selection of wingtips ---------- 05
Figure 1.6 Winglet ---------------------------------------------------- 06
Figure 1.7 C-wing ---------------------------------------------------- 06
Figure 2.1 Span efficient of various nonplanar shapes ----------- 11
Figure 2.2 C-wing geometries analysis ---------------------------- 11
Figure 3.1 Planform of the imitated X-48 ------------------------- 15
Figure 3.2 Nose part of the planform ------------------------------- 16
Figure 3.3 Position of airfoil station -------------------------------- 16
Figure 3.4 Airfoil at station 1 to 3 ---------------------------------- 17
Figure 3.5 Airfoil at station 4 to 9 ---------------------------------- 17
Figure 3.6 Airfoil at station 10 -------------------------------------- 17
Figure 3.7 Wing offset and dihedral -------------------------------- 18
Figure 3.8 Yang BWB ------------------------------------------------ 19
Figure 3.9 Yang BWB - top view ----------------------------------- 19
Figure 3.10 Yang BWB - after view --------------------------------- 19
Figure 3.11 Yang BWB - side view ---------------------------------- 19
Figure 3.12 Winglet express ------------------------------------------ 20
Figure 3.13 Wing let platform of imitative X-48 ------------------- 20
Figure 3.14 C-wing express ------------------------------------------- 20
VII
Figure 3.15 Vertical plan of C-wing (imitative X-48) ------------- 21
Figure 3.16 Horizontal plan of C-wing (imitative X-48) --------- 21
Figure 3.17 Vertical plan of C-wing (Yang BWB) ----------------- 22
Figure 3.18 Horizontal plan of C-wing (Yang BWB) ------------- 22
Figure 3.19 Diagram of structured grid ----------------------------- 24
Figure 3.20 Diagram of unstructured grid -------------------------- 24
Figure 3.21 Computational domain (structured grid) -------------- 25
Figure 3.22 Surface meshes (structured grid) ---------------------- 25
Figure 3.23 Meshes on symmetric plane (structured grid) -------- 26
Figure 3.24 Computational domain (unstructured grid) ----------- 27
Figure 3.25 Surface meshes (unstructured grid) ------------------- 27
Figure 3.26 Meshes on symmetric plane (unstructured grid) ----- 28
Figure 3.27 Target twist foil positions ------------------------------- 33
Figure 3.28 Diagram of twist angle on airfoil ---------------------- 33
Figure 3.29 Quadratic interpolation ---------------------------------- 34
Figure 3.30 Powell's method ----------------------------------------- 35
Figure 3.31 Projection plane of M6 wing --------------------------- 37
Figure 3.32 Airfoil of M6 wing -------------------------------------- 37
Figure 3.33 M6 wing section 01 -------------------------------------- 39
Figure 3.34 M6 wing section 02 -------------------------------------- 39
Figure 3.35 M6 wing section 03 -------------------------------------- 40
Figure 3.36 M6 wing section 04 -------------------------------------- 40
Figure 3.37 M6 wing section 05 -------------------------------------- 41
Figure 3.38 M6 wing section 06 -------------------------------------- 41
Figure 3.39 M6 wing section 07 -------------------------------------- 42
Figure 3.40 Wall Y-Plus on the lower surface of M6 wing (structured
VIII
grid) -------------------------------------------------------- 42
Figure 3.41 Wall Y-Plus on the upper surface of M6 wing (structured
grid) -------------------------------------------------------- 43
Figure 3.42 Wall Y-Plus on the lower surface of M6 wing
(unstructured grid) --------------------------------------- 43
Figure 3.43 Wall Y-Plus on the upper surface of M6 wing
(unstructured grid) --------------------------------------- 44
Figure 3.44 CL comparison with Song's data ----------------------- 45
Figure 3.45 CD comparison with Song's data ---------------------- 46
Figure 3.46 LD comparison with Song's data ---------------------- 46
Figure 3.47 CL comparison between structured and unstructured grid
----------------------------------------------------------------- 48
Figure 3.48 CD comparison between structured and unstructured grid
----------------------------------------------------------------- 49
Figure 3.49 LD comparison between structured and unstructured grid
----------------------------------------------------------------- 49
Figure 4.1 CL result of Yang BWB --------------------------------- 50
Figure 4.2 CD result of Yang BWB -------------------------------- 51
Figure 4.3 LD result of Yang BWB -------------------------------- 51
Figure 4.4 CL result of imitative X-48 ----------------------------- 52
Figure 4.5 CD result of imitative X-48 ---------------------------- 52
Figure 4.6 LD result of imitative X-48 ----------------------------- 53
Figure 4.7 Pressure contours of Yang BWB at AOA 2.0 degree (upper
surface) ---------------------------------------------------- 55
Figure 4.8 Pressure contours of Imitative X-48 at AOA 1.0 degree
(upper surface) ------------------------------------------- 56
IX
Figure 4.9 Pressure contours of Yang BWB at AOA 2.0 degree (lower
surface) ---------------------------------------------------- 56
Figure 4.10 Pressure contours of imitative X-48 at AOA 1.0 degree
(lower surface) ------------------------------------------- 57
Figure 4.11 Pressure contours of imitative X-48 after optimisation
work (upper surface) ------------------------------------ 58
Figure 4.12 Pressure contours of imitative X-48 after optimisation
work (lower surface) ------------------------------------ 59
X

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