等离子体鞘套数值仿真及其与电磁波相互作用

发布时间：2018-03-15 11:19

本文选题：等离子体鞘套　切入点：高超声速流体　出处：《西安电子科技大学》2016年博士论文　论文类型：学位论文

【摘要】：自飞行历史上第一次达到高超声速,人类对高超声速飞行的研究便开始进入到不断的深入和发展之中。各种航空飞行器在再入过程中达到的高超声速,各航空大国积极投入研究的临近空间高超声速飞行器,在带来先进性的同时,也带来了不可忽视的问题。在高超声速飞行中产生的高温效应,使飞行器绕流流场中的气体产生了离解、电离等一系列化学反应,使流场形成一团电离气体,称为等离子体鞘套。等离子体鞘套与电磁波之间的相互作用对飞行器与地面的通讯以及雷达对飞行器的探测识别作用造成了不可小觑的影响。等离子体鞘套的存在甚至造成通讯黑障现象,对飞行任务的安全性乃至成功与否带来隐患。针对这一现象,研究者们从等离子体鞘套的流场分布特性入手,在等离子体鞘套的形成机理、组成结构以及数值仿真方法等方面进行了大量的研究工作,并在此基础上进行了大量的电磁波与等离子体鞘套相互作用的研究,以解决等离子体鞘套对高超声速飞行带来的种种问题。本文以有限体积方法为基础,建立基于多块近似结构网格的计算网格,通过求解积分形式的流体控制方程-纳维斯托克斯方程对飞行器绕流流场进行数值仿真,采用隐式LU-SGS时间推进方法进行三维粘性流动计算,形成计算程序。程序中包含多种基于迎风方式的对流通量差分格式,以AUSM类格式为主,并通过Reminne问题将几种通量分裂差分格式进行对比分析。通过计算程序进行包覆飞行器流场的数值仿真模拟,将采用量热气体模型计算得到的流场与采用热化学非平衡计算得到的流场进行对比,总结两模型对流场仿真结果的影响。在以上有限体积计算流体力学方法的热完全气体流场仿真程序的基础上,引入热动力学模型和化学动力学模型,使其能够进行热非平衡、化学非平衡流场的数值仿真计算。采用双温度模型以及不同的七组元化学反应动力学模型,对热力学非平衡以及化学非平衡绕流流场进行求解,形成对高超声速热化学非平衡流场的计算程序,计算采用不同化学反应模型得到的流场分布并进行对比分析。通过现有文献中提供的计算和实验结果,验证了程序进行热动力学非平衡和化学非平衡流场计算的可行性和可靠性。进行电磁波与等离子体层相互作用分析,通过电磁波在等离子体层中传播的传输系数、反射系数和吸收系数对两者之间的相互作用进行描述。讨论等离子体层所具有的非均匀特性对电磁波传播的影响,以及存在外加磁场时电磁波在离子体层中的传播。以解决通讯黑障问题的为应用背景,将入射电磁波频率提高到太赫兹波段,为解决通讯中断问题提供理论参考。进行不同飞行场景下圆球绕流流体的计算,场景变化包括飞行马赫数以及飞行高度,分析比较等离子体鞘套随飞行高度和飞行马赫数的变化规律以及造成该变化的原因。得出不同飞行场景下的包覆球体等离子体气体的电子密度分布,计算相应的等离子体频率和等离子体碰撞频率。进行不同飞行场景下典型钝锥绕流流场的计算,飞行场景为RAM试验中飞行轨迹上的几个典型高度,得出电子密度以及相应的等离子体鞘套和碰撞频率,提取驻点线上流场特性进行介电系数转化,并计算驻点线上垂直入射电磁波的单程和双程传输。同时提取非驻点线上的流场特性参数进行介电系数转换,并计算电磁波再非驻点线上的传输。将通过不同传输路径得到的结果进行比较分析。
[Abstract]:Since the first time in the history of flight of hypersonic flight on hypersonic research, humans began to enter into the constant deepening and development. All kinds of aircraft in hypersonic reentry to the near space hypersonic aircraft aviation powers researched actively, bring in advanced at the same time, also brought the problem can not be ignored. The effect of high temperature generated in hypersonic flight, the aircraft flow around the gas flow field in the dissociation, a series of chemical reactions such as ionization, causes the flow to form a group of ionized gases, called plasma sheath. Detection and identification of interaction between electromagnetic wave and plasma sheath of aircraft with the ground communication and radar on the aircraft caused underestimated impact. The existence of the plasma sheath communication and even cause blackout phenomenon, the flight safety Full of success and risks. In view of this phenomenon, the researchers start from the plasma sheath flow distribution characteristics, the formation mechanism of plasma sheath, the composition structure and the method of numerical simulation for a lot of research work, and on the basis of a large number of electromagnetic wave and plasma sheath study on the interaction, to solve the problems of plasma sheath on the hypersonic flight brought. Based on the finite volume method, a multi block grid structure based on grid approximation, by solving the governing equation of fluid product form of the Navier Stokes equations for numerical simulation of flow around the aircraft, using the implicit LU-SGS time advance method for 3D viscous flow calculation, the formation of convective flux calculation program. Based on the upwind difference scheme contains a variety of procedures, based on AUS M format, and several flux splitting scheme were analyzed by Reminne. By numerical simulation of flow field of the aircraft coating through computer program, the flow field will flow calculated with thermochemical nonequilibrium obtained by the calorimetric gas model were compared, summed up two models influence flow field simulation results computational fluid dynamics method. Based on the above finite volume thermal perfect gas flow simulation program, the introduction of a thermal kinetic model and kinetic model, which can calculate the thermal non-equilibrium, numerical simulation of chemical non equilibrium flow. The two temperature model and seven different components of chemical reaction kinetics, thermodynamics of non balance and non balance of the chemical solution of flow flow, the formation of the calculation program of hypersonic thermochemical nonequilibrium flow, calculated by different The chemical reaction model of flow field distribution were analyzed. The calculated and experimental results provided by existing literature, to verify the procedures for thermal and chemical non-equilibrium dynamics of the feasibility and reliability of equilibrium flow calculation. The electromagnetic wave and plasma layer interaction analysis, the transmission coefficient of electromagnetic wave propagation in plasma layer., to describe the interaction between reflection coefficient and absorption coefficient of plasma layer is discussed. Effects of inhomogeneous characteristics of electromagnetic wave propagation, and the presence of an applied magnetic field of electromagnetic waves in the plasma layer in the transmission. In order to solve the communication blackout as the application background, will increase the frequency of the incident electromagnetic wave to terahertz in order to solve the problem of communication interrupt band, and provide a theoretical reference. To calculate the flow around the sphere of the different flight scenarios, including flying scene change For Maher number and flight height, cause analysis and comparison of plasma sheath with flight altitude and flight Maher numbers and the changes caused by the changes of the electron density distribution obtained. Different flight scenarios covering sphere plasma gas, calculate the plasma frequency and plasma collision frequency. The calculation flow around the blunt cone under typical different flight scene, flying scenes for several typical high flight trajectory in RAM test on the obtained electron density and the corresponding plasma sheath and collision frequency, extracting line upper field characteristics of dielectric coefficient transformation, and calculate the stagnation line perpendicular to the incident electromagnetic wave of a one-way and two-way transmission. At the same time, extraction of non flow characteristic parameters of stagnation the line of dielectric coefficient conversion, and the calculation of the electromagnetic wave and transmission line. The stagnation point through different transmission path to The results were compared and analyzed.

【学位授予单位】：西安电子科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：V219

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