本研究以F-22匿蹤戰鬥機為研究目標，對F-22匿蹤戰鬥機體外型進行空氣動力(Aerodynamics)之計算和分析，並將傳統尾翼設計改為V型尾翼布局，探討其氣動力性能差異，嘗試研究國外先進飛行器設計，建立匿蹤戰鬥機分析方法及提供我國下一代匿蹤戰鬥機設計參考。本研究將F-22全機建模後，運用商業套裝軟體ANSYS FLUENT進行F-22氣動力外型之外部流場穿音速及超音速之數值模擬。數值研究上使用ANSYS FLUENT高階數值方法，求解穩態可壓縮流那威爾-史托克方程式(Navier-Stokes equations)，以探討F-22空氣動力特性。在紊流模型上，採用SST (Shear-Stress Transport) k-w Model紊流模型。計算網格由ANSYS Meshing產生非結構性網格，搭載混合型網格，於機身壁面周圍建立菱柱型網格(Prism Mesh)以模擬邊界層黏性流場，其他計算領域則使用四面體及六面體網格(Tetrahedron & Hexahedron Mesh)，分析模擬結果之升力係數、阻力係數及各項力矩係數之關係，並進一步探討在偏轉控制面後之性能差異。本研究探討F-22原型機(baseline)及其V型尾翼(V-tail)外傾角45°、60° 及75°空氣動力，其中在穿音速及超音速中F-22原型機與V型尾翼三種外傾角外型在高攻角時出現明顯升力、阻力及俯仰力矩之差異。雖升阻比則在各攻角皆極為相似。在超音速中偏轉升降舵及方向舵可發現新型F-22 V型尾翼β=45°及β=60°外形設計，雖在高攻角時會產生較高之正向俯仰力矩，但在偏航(Yawing moment)時表現較高之效率，若配合控制面轉動，亦能符合飛控穩定之要求，其次不管在穿音速及超音速飛行中皆提供較小之阻力，前世代之飛機要求高升力，而隨著發動機技術的成熟及先進的發展，慢慢轉變為利用速度換取升力，而降低阻力則為最經濟且實際之目標。綜合以上空氣動力分析，本研究建議下一代匿蹤戰機未來可使用V型尾翼布局，外傾角約落於β=45°至60°之間具有良好之空氣動力性能，不論在超音速巡航及飛行操控上皆有較好空優性能。

This study proposes a study of F-22 stealth fighter by analyzing its aerodynamic performance. In additional to learn how F-22 performance is, this study modifies the tail configuration from conventional arrangement to V-tail to investigate the difference in aerodynamic performance. After F-22 full-body surface mesh modeling, one can simulate flow field around F-22 under transonic and supersonic flight conditions, and analyze the lift, drag and moment coefficients, as well as flow field of F-22 fighter at high angle of attack. High-order numerical method to solve Navier-Stokes equation is applied to investigate flow field characteristics of F-22. About turbulence model, SST (Shear-Stress Transport) k-w model is used. In this study, the original model (baseline) and the V-tail configurations with three tilt angles β = 45°, 60° and 75° were established respectively. Major differences in lift, drag and pitching moment are found at high angle of attack. The lift to drag ratio is very similar at all angles of attack under transonic and supersonic. The V-tail with tilt angles β = 45° & 60° show the outstanding flight control performance under supersonic when the elevator and rudder deflection. Besides pitching moment, V-tail with tilt angle β = 45° & 60° have high efficiency during yawing, and lower drag under both transonic and supersonic speed. Based on the above aerodynamic analysis in this study that V-tail configuration is suggested for the next generation stealth fighter design. The V-tail tilt angle should be between β=45°and 60° that will have superior aerodynamic performance during supersonic cruise.

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