隨著國防科技的進步，各國間的武力競爭越演越烈，生產出的砲彈 射程比以往更加的遠，速度也都突破了音速，身為國軍一員，希望藉由 本次的研究分析榴彈砲的流場變化，來研究出如何提升榴彈砲的射程及速度。
本次實驗將使用 Ansys-CFD 套裝軟體 Fluent 來做 155mm 榴彈砲飛 行過程中的各項數據分析，藉由改變榴彈砲馬赫數及榴彈砲的船尾角度， 探討其阻力係數、壓力場、速度分佈圖、壓力分佈圖，在榴彈砲的飛行過程中，阻力係數的變化對提升射程及射速有很大的影響，本次研究也會透過此項特點來做改善，以提升榴彈砲的性能。
透過改變馬赫數可發現榴彈砲周圍的震波，隨著馬赫數的增加由弓 形震波轉變成斜震波，壓力也隨之增加，透過模擬結果可發現次音速時 阻力係數隨著馬赫數的增加隨之上升，當達到 1 馬赫時為阻力係數最高 峰，接著隨之下降。
透過改變船尾形後彈體角度，可發現不同的馬赫數下皆有其最佳的 船尾角度，船尾角度與阻力係數並非成線性成長，但可得知有船尾角度 的榴彈砲在次音速的部分比沒有船尾角度的榴彈降低了約 43%的阻力， 在超音速的部分降低了約 8.5%。

As military technology developments have heated the arms race between nations, so have advancements in artillery technology, with increases in range and artillery rounds traveling at supersonic speeds. As a member of the armed forces, I hope to increase the speed and range of artillery projectiles by using this study to analyze their flow field changes.
In an effort to adjust the projectile’s Mach number and boattail angle, this experiment uses Ansys Fluent CFD software to conduct data analysis on the 155mm projectile’s flight, utilizing the information to explore its drag coefficient, pressure field, velocity profile, and pressure distribution diagram. Any changes in the drag coefficient will significantly impact the range and speed of the artillery projectile during its flight; thus, this research seeks to enhance the artillery projectile’s performance by improving this specific feature.
Mach number information revealed that as artillery projectiles increased in speed, their surrounding shock waves changed from bow shocks to oblique shocks, and their pressure gradually increased. In addition, simulations revealed that the drag coefficient in subsonic speeds would increase with any increases in Mach number, peaking at 1 Mach before subsequently decreasing.
By changing the angle of the boattailed afterbody, we can see that there is an optimal boattail angle for different Mach numbers. Although the boattail angle and drag coefficient do not display linear growth, artillery projectiles with boattail angles reported drag 43% lower than those without boattail angles in subsonic speeds, and reported drag 8.5% lower in supersonic speeds respectively.

1. Suliman, M., et al. Computational investigation of base drag reduction for a projectile at different flight regimes. in International Conference on Aerospace Sciences and Aviation Technology. 2009. The Military Technical College.
2. Viswanath, P., Flow management techniques for base and afterbody drag reduction. Progress in Aerospace Sciences, 1996. 32(2-3): p. 79-129.
3. Wessam, M. and Z. Chen. Firing precision evaluation for unguided artillery projectile. in 2015 International Conference on Artificial Intelligence and Industrial Engineering. 2015. Atlantis Press.
4. Wessam, M.E. and Z.H. Chen. Aerodynamic characteristics of unguided artillery projectile. in Advanced Materials Research. 2014. Trans Tech Publ.
5. Reddy, D.S.K., P.K. Sah, and A. Sharma. Prediction of Drag Coefficient of a Base Bleed Artillery Projectile at Supersonic Mach number. in Journal of Physics: Conference Series. 2021. IOP Publishing.
6. Wilcox, D.C., Turbulence modeling for CFD. Vol. 2. 1998: DCW industries La Canada, CA.
7. Menter, F.R., M. Kuntz, and R. Langtry, Ten years of industrial experience with the SST turbulence model. Turbulence, heat and mass transfer, 2003. 4(1): p. 625-632.
8. Robert L. McCoy, "Modern Exterior Ballistics", 4thedition. ISBN-0-7643-0720-7, Schiffir Publishing Ltd, 1998.