由於地球村的發展，對於超音速飛行的需求逐漸迫切，但超音速產生之巨大阻力會嚴重降低經濟效應，所以對於超音速阻力的降低，有許多的研究不斷進行，其中以外加能量電離氣體的方式，已在多國進行廣泛的研究。電離氣體後產生的離子，可以造成空氣阻力的降低，但是因其內部反應的複雜性，及其相關機制仍在探索中。

　　本文主要研究是以有限體積法分析，利用CFD-FASTRAN計算流體力學軟體加以計算、求解Navier-Stokes方程式，並配合動力理論、非平衡流、質量擴散模型、來源項計算、及紊流模型等，以氣體中的各成份(species)，在電離反應方程式的反應率下，進行對弱電離氣體的流場計算。另外使用同一模型的前提下，討論無電離及有電離氣體物理特性比較，其中包括密度、壓力、溫度、阻力等變化。

　　本研究從參考實驗加以對照，並模擬不同參數下，各流場數值的變化，其中參數有：分子內部溫度及電離度。結果發現當電離度及分子內部溫度越高時，整體弱電離氣體對於流場壓力和密度的變化將會加大；亦即，當電離度及分子內部溫度提高時，流場物體的阻力係數將會降低2~4%。

　According to the increasing requirements of global transportation, the applications in supersonic flight are getting more and more important. Due to the increased drag of supersonic flight, the economic benefits of the higher speed would be reduced. There are many studies are introduced. Joining energy in and ionize the gas is one of the methods to solve the problem. After the gas is ionized, the ions could decrease the aerodynamic drag, but the physical mechanism is very complicated.

　This study utilizes CFD-FASTRAN software. The software calculates Navier-Stokes equations, includes kinetic theory, thermal non-equilibrium, mass diffusivity, source term, and turbulence models. The weakly ionized plasma flow field is calculated by the species of the gas, which is based on the assumption of a fixed ionized degree.

　It is found that the molecular internal temperatures and the ionized degrees are changed in this study. The results show that the drag coefficient of the flying body is decreased by 2~4% when the molecular internal temperature and the ionized degree become higher.

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