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Static and Dynamic Aerodynamic Comparisons for Stealthy/Conventional Aerial Vehicles in Water Tunnel
|關鍵字:||X-45A Stealth Shape|
Static/Dynamic Aerocharacteristics Comparison
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|摘要:||本文主要是利用水洞試驗研究具有匿蹤外形之Boeing X-45A模型與傳統非匿蹤外形之NASN TP-1803比較其渦流流場與氣動力特性。實驗結果顯示：於靜態俯仰過程中且低攻角範圍（α < 20°）不僅X-45A正向力係數Cn的增加大於TP-1803正向力係數的增加，而且縱向穩定性上X-45A也優於TP-1803。然而α > 20° 之後TP-1803的Cn值反而會大於X-45A的Cn值，而且X-45A之縱向不穩定性會較早發生。α < 20° 範圍中，X-45A在靜態上仰過程之正向力係數是快速的增加，下俯過程之正向力係數是緩慢的減少。然而TP-1803上仰/下俯過程Cn值表現出相近的線性增減。動態俯仰過程結果顯示TP-1803會比X-45A產生更大的正向力遲滯。此外由於動態上仰過程X-45A之最大俯仰力矩Cm大於TP-1803，因此X-45A是會比TP-1803產生更大的縱向不穩定性。另外X-45A在各種頻率（K）之俯仰過程中α-Cn曲線均呈現順時針的遲滯環特徵。而且當K值增加模型所產生之遲滯行為會更為明顯，於低攻角範圍中上仰過程的縱向不穩定性以及下俯過程縱向穩定性均會更為顯著。|
This paper highlights the water tunnel experiments of both the Boeing X-45A stealth drone model and the traditional NASA TP-1803 model without semblance of stealth, and compares their wing vortex structures and aerocharacteristics for several parameters. The experiments show that the normal force coefficient (Cn) of the X-45A increases much more than that of the TP-1803 for α < 20° in the static processes, and the X-45A has better longitudinal stability than the TP-1803. For α > 20°, the Cn of the TP-1803 is larger than that of the X-45A. Further, the longitudinal instability of the X-45A occurs earlier than the TP-1803. Further, For α < 20° the Cn of the X-45A increases rapidly in the pitch-up process, but decreases slowly for the pitch-down process. The Cn of the TP-1803 occurring in the pitch up/down processes are approximately linear at α < 20°. The dynamic normal fore experiment shows more tremendous hysteresis for the TP-1803 than the X-45A. In addition, in the pitch-up process, the maximum Cm in the X-45A is larger than that of the TP-1803, hence the longitudinal stability of the X-45A appears more instable at maximum Cm, as compared to the TP-1803. Besides, the X-45A for different reduced frequency (K) processes, the curves of α-Cn all exhibit clockwise patterns, with similar hysteresis loop characteristics. Moreover, as the reduced frequency increases hysteresis behaviors becomes more obvious. The longitudinal instability appears clearer in the pitch-up processes and the longitudinal stability appears for low AOA in the pitch-down processes.
|Appears in Collections:||機械工程學系所|
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