Research On Radiation Characteristics And Transmission Effect For The Outflow Field Shock Around High-speed Aircraft Hood

The shock radiated field outside high-speed aircraft causes serious interference on the imaging detector inside hood. The paper carries out research on radiation characteristics and transmission effects for the outflow field shock, to improve image quality and performance of infrared detector in high-speed aircraft.The main contents of this paper include shock flow field modeling and meshing, calculation and simulation of the radiation characteristics and transmission effects for the flow field. The Gambit can complete rendering and meshing shock flow field by using unstructured triangular mesh method, the model can simulate a normal shock flow field.The calculation’s idea of radiation characteristics is that the gaseous medium is seen as an absorbent scattering media, the shock radiation is seen as a kind of radiation-convection-thermal coupling problem. An accurate, stable and efficient physical calculation model can be got by researching Finite Element Method and various physics equations of heat transfer, and solving the Galerkin finite element discretization on the control equation, such as energy equation, radiative transfer equation and flow equation. Then it’s necessary to adopt Upwi nd Finite Element Method to make the solution more stable.The Matlab is used to simulate radiation-thermal coupling part and convection part, the temperature field of convection part is solved alone, and as the convective terms substituted into the energy equation to obtain temperature field of radiation-convection-thermal coupling model. The paper gets the temperature and the radiation intensity distribution, and analyze important parameters of the medium: medium albedo, boundary emissivity and Planck value, the following conclusions can be obtained: the lower medium albedo, the stronger the radiation intensity; the lower boundary emissivity, the stronger radiation intensity; the lower the Planck value, the stronger the radiation intensity. The conclusion is consistent with theoretical analysis, and lays the foundation for future study on radiative transfer effects for shock flow field.The simulation’s idea of transmission effects for the flow field based on Matlab is that since no particle is present in the shock flow field, the total value of radiation intensity is a linear superposition of every layers along an angle of sight at a certain point on the inner surface. Every point reaching the inner surface is met radiation Bragg law. The graph of intensity-radiation-points can be obtained with different parameters, it can be found that media albedo and Planck value have little effect on the simulation results, but boundary emissivity makes a great influence on the simulation results. The method can obtain radiation intensity values in each light point and each radiation direction.The simulation model can be applied for different shape of the hood and different locations of imaging detector, and achieve quantitative analysis on detector imaging interference by shock flow field radiation.