Radiation Characteristics And Coupled Heat Transfer Analysis Of Inhomogeneous Media Based On The Runge-kutta Algorithm

The problem of radiation transmission in inhomogeneous media is widespread in engineering.Graded refractive index phenomena due to thermal effects often cause problems in engineering technology and even endanger the safety of the equipment.On the other hand,the optical signal transmission characteristics can be changed by designing the refractive index distribution of the medium in the project,and equipment performance and technological innovation can be effectively improved.Eliminating the dangers of graded refractive index or thermal analysis and thermal design of optical components require adequate investigation of the radiative transfer problem of graded index media.The numerical method for solving the radiation transmission of gradient index media has been studied.However,most of the solution methods currently solve the ray transmission trajectories by region discretization,which has poor applicability in complex refractive index media.In order to study the radiative transfer problem of threedimensional arbitrary refractive index distribution media,this paper adopts Runge-Kutta optical trajectory solving method and moving least squares fitting method to accurately solve the ray trajectories in media with discrete distribution of 3D refractive index data.Then,combining the Runge-Kutta ray tracing method with the Monte Carlo method,a numerical solution method for radiation transmission in a 3D inhomogeneous medium has been established.Taking the optical window as the research object,the effects of different refractive index distribution forms on the radiation characteristics of the window dielectric were analyzed by using the radiation solution method of this paper.And the projection properties of gradient refractive index media on various external light sources were studied.The physical properties of the actual translucent material are often a function of temperature and wavelength.In this paper,a spectral band approximation method is used to establish a numerical method for the spectral radiation characteristics of a material with changing property.The visible radiation characteristics of a quartz window with known temperature field are analyzed.In order to fully study the optical-thermal coupling problem of optical windows,the finite-volume method is used to solve the thermal conduction equation.Combined with the numerical solution of heterogeneous radiation,a numerical model of radiation and thermal conduction coupled heat transfer in optical window with changing property is established.For the radiation-conduction coupling problem of a deformable optical window,this paper analyzes the effects of temperature variation of optical parameters on the temperature field and surface radiation characteristics of the medium under different radiation boundary conditions.The results show that the increase of the refractive index with the temperature change rate will cause the temperature distribution of the medium to be uniform.Simultaneously,the energy of the exiting radiation of the surface will gradually increase due to the focusing of the light.And the change trend of the photothermal characteristics decreases with the increase of the optical thickness.