Influence Of Structural Parameters Of High-Speed Aircraft Fairing With Revolution Symmetry On External Flow Field Characteristics

The fairing is located at the forefront of the high-speed aircraft.Its configuration has a great influence on the air resistance and external flow characteristics of the aircraft.The air resistance determines the range of the aircraft,and the external flow characteristics affect the detection and recognition capability of the aircraft..When the aircraft moves at high speed in the atmosphere,there is a high relative velocity between the flow field and the aircraft,and the air at the front end of the fairing is strongly compressed,and a distinct shock layer appears.The density and refractive index of the nearby area increase and exhibit a distinct non-uniform distribution.The pressure on the outer surface of the fairing increases and the heat flux increases.These aerodynamic effects work together to make the light passing through the flow field uneven.The phase delay causes the detector to deviate during imaging,affecting the ability of the aircraft to detect and track the target.In this paper,based on the finite element method,the calculation model of the flow field outside the fairing is established.The external flow field characteristics of quadric surface,von Karman surface and sinusoidal surface fairing with length to diameter ratio of 0.5 to 2(step length 0.1)were simulated and analyzed.The density field distribution of the external flow field of various configurations and the distribution of the pressure field on the outer surface of the fairing and th e distribution of heat flux density were analyzed.The variation of the external flow field characteristics with the length-to-diameter ratio of the fairing and the surface shape of the fairing was analyzed.The effects of the length-to-diameter ratio,the base circle radius and the bottom slope of the fairing on the air resistance coefficient of the aircraft are studied.According to the Gladstone-Dale formula and the density field data of the external flow field,the refractive index field of the external flow field is calculated.Based on the fourth-order Runge-Kutta method,the optical transmission calculation model of the gradient refractive index medium is established.The optical transmission performances of the quadric surface,von Karman surface and sinusoidal fairing flow field with length-to-diameter ratio of 1.5 were calculated.The relationship between the light transmission performance of the flow field outside the fairing and the surface shape of the fairing is analyzed.