【摘要】：本文以火星探測為研究背景,針對飛行器高超聲速再入火星稀薄大氣過程中的流動問題,采用直接模擬蒙特卡羅方法(the Direct Simulation Monte-Carlo method,DSMC)開展研究,考慮熱化學非平衡效應(yīng),發(fā)展了一套可求解火星大氣稀薄流動的DSMC數(shù)值模擬程序。首先分析了火星環(huán)境特征和探測關(guān)鍵技術(shù),基于火星大氣高稀薄程度的特點,確定了采用DSMC方法模擬火星大氣高超聲速流動的技術(shù)途徑。其次,梳理了DSMC方法模擬稀薄氣體流動所涉及的分子氣體動力學、統(tǒng)計熱力學基礎(chǔ)理論,闡述了DSMC方法的算法實現(xiàn)過程,結(jié)合基本算例對本文程序予以驗證。根據(jù)研究工作中的經(jīng)驗,提出網(wǎng)格劃分、模擬分子數(shù)設(shè)定、計算量預(yù)估等方面的一些建議。然后,研究了火星大氣化學反應(yīng)DSMC方法的實現(xiàn),分析了CO_2分子振動模態(tài),給出多原子分子振動能松弛在DSMC中的實現(xiàn)方法,建立火星大氣化學反應(yīng)模型并將其嵌入DSMC方法中,發(fā)展了一套可用于火星大氣稀薄流化學反應(yīng)效應(yīng)計算與分析的求解程序,采用不同組元反應(yīng)算例對程序予以驗證,在此基礎(chǔ)上研究了火星大氣熱化學非平衡效應(yīng)。最后,基于本文發(fā)展的火星大氣稀薄流DSMC計算程序,研究了氣體稀薄程度對流場特性的影響,總結(jié)了流場結(jié)構(gòu)隨努森數(shù)的變化規(guī)律,在此基礎(chǔ)上提出了一種稀薄流流場預(yù)估的經(jīng)驗方法,并運用該方法成功預(yù)估了高超聲速圓柱繞流激波位置。本文發(fā)展的計算技術(shù)可對高超聲速稀薄流場特性與氣動特性進行數(shù)值模擬與分析,可用于地球、火星大氣環(huán)境下的飛行器再入問題的求解,對工程設(shè)計具有一定的參考價值和指導(dǎo)意義。
[Abstract]:Taking Mars exploration as the research background, this paper aims at the flow problem in the rarefied atmosphere of the aerocraft, using the direct simulation Monte Carlo method (the Direct Simulation Monte-Carlo method, DSMC) to develop a set of DSMC numbers that can solve the rarefied flow of the Mars atmosphere by considering the thermal chemical nonequilibrium effect. Value simulation program. Firstly, the characteristics of the Mars environment and the key detection techniques are analyzed. Based on the characteristics of the high rarefied atmosphere, the DSMC method is used to simulate the hyperhypersonic flow of the Martian atmosphere. Secondly, the DSMC method is used to simulate the molecular gas dynamics involved in the flow of thin gas and the basis of statistical thermodynamics. In this paper, the implementation process of the algorithm of DSMC method is expounded, and the basic calculation is used to verify the program. According to the experience in the study, some suggestions on the mesh division, the simulation of the number of molecules, the prediction of the amount of calculation are proposed. Then, the realization of the DSMC method for the chemical reaction of the Martian atmosphere is studied, and the vibration modes of the CO_2 molecules are analyzed. A solution to the relaxation of multi atomic molecules in the DSMC is developed, and the chemical reaction model of the Martian atmosphere is established and embedded in the DSMC method. A set of solutions which can be used to calculate and analyze the chemical reaction effect of the thin thin flow of the Mars atmosphere is developed. The program is verified by the different component reaction examples. On this basis, the fire is studied. The thermal chemical nonequilibrium effect of the star atmosphere. Finally, based on the DSMC program of the rarefied flow in the Martian atmosphere, the influence of the degree of gas thinning on the characteristics of the flow field is studied. The change law of the flow field structure with the Knudsen number is summarized. On this basis, an empirical method for predicting the flow field of thin flow is proposed, and the method is successfully estimated with this method. The calculation technique developed in this paper can be used to simulate and analyze the characteristics and aerodynamic characteristics of hypersonic rarefied flow field, which can be used to solve the reentry problem in the earth and Mars atmosphere, which has a certain reference value and guiding significance for the engineering design.
【學位授予單位】：南京航空航天大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：V411

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