Numerical Simulation And Analysis Of Aero-optical Effect Of The 3D Hypersonic Aircraft

During flight,the structure of the flow field around the aircraft with an optical system will change due to the air compression,which will result in complex flow field structure such as the shock wave,expansion wave and turbulent boundary layer.These phenomenons can let the image on the detector blur,offset and jitter,and reduce detection and aiming accuracy.With the rapid development of military science and aerospace technology,the speed of the aircraft is continuously increased,the aerodynamic effect is increased,too,which will impair the image quality.So a thorough study of the mechanism of aero-optical effect and a deep understanding of the relationship between imaging quality and the structure of the flow field are the theoretical basis for improving the ability of image correction and effective aiming control.In this research,the background and significance of the research on aero-optical effect are firstly analyzed.The development course of the aero-optical effect and the research status including the development trend at home and abroad are summarized.The main research contents,the structure and arrangement of the thesis are introduced.The focus and difficulty of the research are also described.Secondly,based on the theory of fluid mechanics and aerodynamics,the structural characteristics and effect factors of supersonic flight flow field are analyzed.According to the influence degree of each factor,the main aspects to be studied in this subject are determined.Commonly used flow field and light transmission in homogeneous flow field calculation methods are compared,and the methods suitable for this subject are determined.Thirdly,the single conical vehicle hood with a side window is taken as the research object,and the three-dimensional flow field model is built.The concept and significance of the flow field discretization are introduced.The common meshing methods and their applications are summarized.Gambit is used to achieve the reasonable and effective mesh.Based on the reasonable choice of solving methods and models,the professional fluid mechanics calculation software Fluent is used to simulate the density distribution of the flow field under each flight condition,and the results are verified.At the same time,on the basis of the distribution of the density,the light tracing method is used in combination with the lines creation tool of Fluent to realize the automatic derivation of a large amount of density field data and obtain the wavefront distortion through different flow fields,which simplify the process of ray tracing greatly.By using the method of physical optics,the image quality evaluation functions under each flight condition is obtained.The influence of different flight conditions on the image quality are discussed.Finally,the contents of the work as well as the research results and the shortcomings are summarized.In summary,this research focuses on the impact of the non-uniform flow field on the light transmission of the supersonic aircraft hood under different flight conditions.The work is divided into two main parts: flow field simulation and optical transmission calculation.And finally a comprehensive and quantitative comparative analysis of the different flight conditions on the imaging quality is given.