本研究主旨為透過計算流體力學(CFD,Computational Fluid Dynamic)探討全機在非穩態下於機身表面之流場現象，並了解機身表面之流場結構和穩定與不穩定節點，以便提升機體穩定程度。
首先文獻驗證以模擬低雷諾數三維不可壓縮流65o三角翼(Delta wing)、76o/40o 複合式三角翼(Double delta wing)和可壓縮流四代戰機F-16XL。運用商業套裝軟體ANSYS Fluent進行戰機模型的氣動力外型外部流場數值模擬，在三角翼流場採用高階數值方法求解非穩態不可壓縮之那威爾-史托克方程式(Navier-Stokes Equations)來探討機翼表面流場上之渦流現象，採用分離渦流模擬法(DES, Detached Eddy Simulation)及剪應力傳輸(SST, Shear Stress Transport) k-ω紊流模型，並經由二階迎風法(Second-order upwind)做計算，計算網格則透過Fluent Meshing建製混合型網格，產生結構性及非結構性網格，於物體與流體接觸之壁面周圍建立多面體網格(Polyhedral Mesh)模擬邊界層黏性流場，其餘流體區域則使用六面體網格(Hexahedral Mesh)。另外，使用可壓縮之那威爾-史托克方程式模擬全機在穿音速下之流場，分析渦流(Vortex)、表面摩擦線(Skin friction line)、壓力係數(Cp)、升力係數(CL)以及阻力係數(Cd)。
最後將輸出之數值結果運用穩定性理論(Stability theory)於五代戰機上之各收斂、分離點，透過速度場(Velocity field)方程式與最小平方法(Least squares method)計算穩定性(Stable)與非穩定性(Unstable)的數值比較，並利用特徵值大小比對定點分類(Classification of fixed points)中各螺旋點(Spiral points)、節點(Node)…..等等，藉此判斷所產生之渦流脫落 (Vortex shedding)是否能使機身穩定。

The purpose of this research is to explore the fluid phenomena of unsteady flow of the aircraft through computational fluid dynamics (CFD). Understand the flow structures and the stability of nodes on the surface of aircraft to improve the stability of aircraft performance.
First, three tests, low Reynolds number of a 3D incompressible flow 65o delta wing, 76o/40o double delta wing, and a compressible flow fighter (F-16XL) are simulated and verified with known data. Otherwise, used the commercial software package ANSYS Fluent is used to perform numerical simulation of aerodynamic external flow field of the fighter. The research uses high-order numerical methods to solve unsteady flows. The Detached Eddy Simulation (DES) and Shear Stress Transport (SST) k-ω turbulence model is applied. The structured and unstructured meshes are generated by using Fluent meshing method. The polyhedral meshs were established around the wall surface to simulate the viscous flow field on the boundary layer. And the other regions were established by hexahedral meshs. Second, the aircraft's analysis of vortex, skin friction line, pressure coefficient (Cp), lift coefficient (CL) and drag coefficient (Cd) are investigated.
Finally, the convergence and separation points of the Fifth-generation fighters are investigated by stability theory. Using the velocity field around the surface and least squares method to calculate their eigenvalues to understand the stability and the instability on the vortex nodes.

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