本研究以源自NATO AVT-161任務小組之SACCON構型所發展的 UCAV NCKU模型為研究對象，透過數值模擬方式探討其於低速與穿音速流場下之氣動特性與流場結構。研究目的在於分析不同流動條件下之表面壓力分佈、升阻力特性與渦流行為，並評估壓縮性效應對 UCAV 氣動表現之影響。
數值模擬採用 ANSYS Fluent 軟體進行。低速條件設定為來流速度 19.16 (m/s)、雷諾數 1.01×10⁵，並於攻角 0°、5° 與 10° 下分別使用 Laminar Solver 與 k-ω SST 紊流模型進行模擬，比較不同解法對壓力係數分佈、升阻力係數與壁面流線之預測差異，並與文獻中之風洞實驗壓力量測與油膜實驗及水洞實驗結果進行比較。穿音速模擬則設定自由流馬赫數為 0.8，採用 k-ω SST 模型並啟用能量方程式，分析0°攻角下之壓力分佈、馬赫數分佈與震波形成位置，同時將數值結果與 Prandtl–Glauert 壓縮性修正理論進行比較，以探討其適用性與限制。
研究結果顯示，在低速條件下，Laminar Solver 於低雷諾數流場中能較準確捕捉前緣分離、逆流區域及Inner vortex結構，其壓力分佈與油膜流線結果與實驗觀察具有良好一致性；相較之下，k-ω SST 模型在部分區域呈現較平滑之流線預測。在穿音速條件下，翼尖區域可觀察到局部音速與超音速區域的形成，顯示壓縮性效應已顯著影響流場結構，且僅以 Prandtl–Glauert 修正已不足以完整描述實際壓力分佈行為。整體而言，本研究釐清了 UCAV 模型於低速與穿音速條件下之氣動特性差異，並可作為未來 UCAV 數值模擬與實驗驗證之參考基礎。

This study investigates the aerodynamic characteristics and flow-field structures of a UCAV NCKU model developed from the SACCON configuration of the NATO AVT-161 project through numerical simulations under low-speed and transonic flow conditions. The objective of this research is to analyze the surface pressure distribution, lift and drag characteristics, and vortex behavior under different flow conditions, and to evaluate the influence of compressibility effects on the aerodynamic performance of the UCAV model.
The numerical simulations are conducted using ANSYS Fluent. For the low-speed condition, the freestream velocity is set to 19.16 m/s, corresponding to a Reynolds number of 1.01 × 10⁵. Simulations are performed at angles of attack of 0°, 5°, and 10° using both the Laminar Solver and the k–ω SST turbulence model. The predictive differences in pressure coefficient distribution, lift and drag coefficients, and wall shear streamlines obtained from the two solvers are examined and compared with wind tunnel pressure measurements, oil-film visualization, and water tunnel experimental results reported in the literature.
For the transonic simulation, the freestream Mach number is set to 0.8, and the k–ω SST turbulence model with the energy equation activated is employed. The analysis focuses on the pressure distribution, Mach number distribution, and shock formation locations at an angle of attack of 0°. The numerical results are further compared with those obtained using the Prandtl–Glauert compressibility correction to examine its applicability and limitations.
The results indicate that under low-speed conditions, the Laminar Solver is able to more accurately capture leading-edge separation, reverse-flow regions, and inner vortex structures in low-Reynolds-number flows, showing good agreement with experimental observations in terms of pressure distribution and oil-film flow patterns. In comparison, the k–ω SST model produces relatively smoother streamline predictions in certain regions. Under transonic conditions, localized sonic and supersonic regions are observed near the wingtip, indicating that compressibility effects significantly influence the flow-field structure, and that the Prandtl–Glauert correction alone is insufficient to fully describe the actual pressure distribution behavior. Overall, this study clarifies the differences in aerodynamic characteristics of the UCAV model under low-speed and transonic conditions and provides a reference for future numerical simulations and experimental validations of UCAV configurations.

[1] S. Tsach, A. Peled, D. Penn, B. Keshales, and R. Guedj, "Development trends for next generation of UAV systems," in AIAA Infotech@ Aerospace 2007 Conference and Exhibit, 2007, p. 2762.

[2] E. Sepulveda and H. Smith, "Technology challenges of stealth unmanned combat aerial vehicles," The Aeronautical Journal, vol. 121, no. 1243, pp. 1261–1295, 2017.

[3] A. Schütte, D. Hummel, and S. M. Hitzel, "Numerical and experimental analyses of the vortical flow around the SACCON configuration," in 28th AIAA Applied Aerodynamics Conference, 2010, p. 4690.

[4] D. Zimper and D. Hummel, "Analysis of the transonic flow around a generic UCAV configuration," in 32nd AIAA Applied Aerodynamics Conference, 2014, p. 2266.

[5] Y.-P. Chen, J.-J. Miau, and Y.-H. Chen, "REYNOLDS NUMBER EFFECTS ON THE VORTEX STATE SWITCH OF UCAV MODEL."

[6] Y.-H. CHEN, J.-J. MIAU, Y.-P. CHEN, and Y.-R. CHEN, "Blunt leading-edge effect on spanwise-varying leading-edge contours of an UCAV configuration," Journal of Fluid Science and Technology, vol. 18, no. 1, pp. JFST0012–JFST0012, 2023.

[7] F. R. Menter, "Two-equation eddy-viscosity turbulence models for engineering applications," AIAA journal, vol. 32, no. 8, pp. 1598–1605, 1994.

[8] A. Inc, "Ansys Fluent Theory Guide, Release 2022 R1," ed: Ansys, Inc Canonsburg, PA, 2021.

[9] S. V. Patankar and D. B. Spalding, "A calculation procedure for heat, mass and momentum transfer in three-dimensional parabolic flows," in Numerical prediction of flow, heat transfer, turbulence and combustion: Elsevier, 1983, pp. 54–73.

[10] A. Schütte, D. Hummel, and S. M. Hitzel, "Flow physics analyses of a generic unmanned combat aerial vehicle configuration," Journal of Aircraft, vol. 49, no. 6, pp. 1638–1651, 2012.

[11] J. G. Leishman, Introduction to aerospace flight vehicles. Embry-Riddle Aeronautical University, 2023.

[12] J. Anderson, "Fundamentals of Aerodynamics, 36 McGraw-Hill education," New York, 2010.

[13] H. Glauert, "The effect of compressibility on the lift of an aerofoil," Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character, vol. 118, no. 779, pp. 113–119, 1928.

[14] K. Chung, J. Miau, and J. Yieh, "Initial operation of astrc/ncku transonic wind tunnel," in 25th Plasmadynamics and Lasers Conference, 1994, p. 2515.

[15] 陳麗宇, "雷諾數效應對不同機翼幾何配置的渦流結構研究," Master Thesis, Institute of aeronautics and astronautics, National Cheng Kung University, 2021.