火星大气稀薄流DSMC数值模拟技术研究

发布时间：2018-08-06 13:13

【摘要】：本文以火星探测为研究背景,针对飞行器高超声速再入火星稀薄大气过程中的流动问题,采用直接模拟蒙特卡罗方法(the Direct Simulation Monte-Carlo method,DSMC)开展研究,考虑热化学非平衡效应,发展了一套可求解火星大气稀薄流动的DSMC数值模拟程序。首先分析了火星环境特征和探测关键技术,基于火星大气高稀薄程度的特点,确定了采用DSMC方法模拟火星大气高超声速流动的技术途径。其次,梳理了DSMC方法模拟稀薄气体流动所涉及的分子气体动力学、统计热力学基础理论,阐述了DSMC方法的算法实现过程,结合基本算例对本文程序予以验证。根据研究工作中的经验,提出网格划分、模拟分子数设定、计算量预估等方面的一些建议。然后,研究了火星大气化学反应DSMC方法的实现,分析了CO_2分子振动模态,给出多原子分子振动能松弛在DSMC中的实现方法,建立火星大气化学反应模型并将其嵌入DSMC方法中,发展了一套可用于火星大气稀薄流化学反应效应计算与分析的求解程序,采用不同组元反应算例对程序予以验证,在此基础上研究了火星大气热化学非平衡效应。最后,基于本文发展的火星大气稀薄流DSMC计算程序,研究了气体稀薄程度对流场特性的影响,总结了流场结构随努森数的变化规律,在此基础上提出了一种稀薄流流场预估的经验方法,并运用该方法成功预估了高超声速圆柱绕流激波位置。本文发展的计算技术可对高超声速稀薄流场特性与气动特性进行数值模拟与分析,可用于地球、火星大气环境下的飞行器再入问题的求解,对工程设计具有一定的参考价值和指导意义。
[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.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：V411

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