超音速光学头罩气动光学效应仿真分析

发布时间：2018-08-31 11:06

【摘要】：飞行器在高速飞行过程中,由于飞行速度达到5马赫,周围空气会与光学头罩发生严重摩擦,引起光学窗口外表面温度升高,产生激波层和边界层等,在目标与光学成像设备之间产生不规则的梯度折射率场,即产生了气动光学效应。气动光学效应会导致系统成像存在光程差,进而造成波像差,产生偏移、抖动、模糊,导引头内的光学成像系统将接收到受影响的目标图像,降低对目标识别、追踪能力。因此对超高音速飞行器气动光学效应的研究在制导方面具有重大意义。本文首先分析了大气气动光学效应的研究历史,尤其是对近些年来气动光学效应研究取得的成就和发展趋势进行了详尽分析。阐述了本文研究主要内容为对飞行速度为5马赫的超高音速飞行器在不同飞行条件平稳飞行时,周围流体分布情况及对成像影响。其次,通过对流体力学进行研究,利用网格建模软件建立了飞行器二维网格模型,本文采用了一种非均匀分布的模型网格对飞行器周围的网格流场进行采样划分。利用动态流体力学有限元分析软件,设定飞行器飞行参数,如飞行攻角和不同环境参数变量,确定边界条件,求解器,求解方法和求解方程,研究了边界层和激波的气动光学效应;调整飞行器飞行攻角与飞行环境参数变量,对结果进行比较分析得出不同参数对飞行器周围流场的影响。再次,本文对光线在流场中传播方式进行了研究分析,结合光线追迹法和物理光学法,通过研究传统的光线追迹法使用了一种固定步长光线追迹法,能够在不影响计算精确度的情况下简化建模难度。最后,本文对所得数据进行了分析得出结果,将仿真结果与理论进行比较,并对结果进行了理论上的解释。综上,本文所研究的主要内容为通过Fluent生成光学窗口周围区域的空气密度离散分布,使用MATLAB读取得到的数据建立折射率的离散分布,并模拟无限远处点源的入射光线,通过固定步长的光线追迹法得到在光学窗口面上波像差分布,并做傅立叶变换得到相面的复振幅分布,进而分析像质评价函数并获得结论。
[Abstract]:During the high speed flight, due to the flight speed of Mach 5, the surrounding air will have serious friction with the optical hood, which will cause the temperature of the outer surface of the optical window to rise, resulting in shock layer and boundary layer, etc. There is an irregular gradient refractive index field between the target and the optical imaging equipment, that is, the aero-optical effect is produced. The effect of aero-optics will lead to the optical path difference in the imaging of the system, which will lead to wave aberration, offset, jitter, blur, and the optical imaging system in the seeker will receive the affected target image and reduce the ability of target recognition and tracking. Therefore, the study of aerodynamic optical effect of hypersonic vehicle is of great significance in guidance. In this paper, the research history of atmospheric aero-optical effects is first analyzed, especially the achievements and development trends of aero-optical effects in recent years are analyzed in detail. The main content of this paper is the fluid distribution and its influence on the imaging of supersonic aircraft with a speed of 5 Mach when it flies smoothly under different flight conditions. Secondly, through the research of fluid mechanics, the two-dimensional mesh model of aircraft is established by using the grid modeling software. A non-uniform distributed model grid is used to sample and partition the grid flow field around the aircraft. Using the finite element analysis software of dynamic fluid dynamics, the flight parameters, such as flight angle of attack and variables of different environmental parameters, are set, boundary conditions, solver, solving methods and solving equations are determined. The aero-optical effects of the boundary layer and shock wave are studied, and the influence of different parameters on the flow field around the aircraft is obtained by adjusting the flight angle of attack and the flight environment parameter variables. Thirdly, this paper studies and analyzes the propagation mode of light in the flow field. Combining the ray tracing method and physical optics method, a fixed step ray tracing method is used by studying the traditional ray tracing method. It can simplify the modeling difficulty without affecting the calculation accuracy. Finally, the results are analyzed, and the simulation results are compared with the theory, and the results are explained theoretically. In summary, the main content of this paper is to generate the discrete distribution of air density in the area around the optical window by Fluent. The discrete distribution of refractive index is established by using the data read from MATLAB, and the incident light of point source in infinite distance is simulated. The wavefront aberration distribution on the optical window surface is obtained by the ray tracing method with fixed step size, and the complex amplitude distribution of the phase surface is obtained by Fourier transform, and the image quality evaluation function is analyzed and the conclusion is obtained.
【学位授予单位】：北京理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：V211

【相似文献】