When an aircraft flies at high speed in a dense atmosphere, the airflow outside the optical window interacts to form a complex flow field structure with irregular and nonuniform refractive index distribution, which makes it difficult to accurately calculate the ray propagation path based on the refractive index field. To solve this challenge, three ray tracing implementation methods with fourth-order accuracy are proposed. By comparing with the spiral ray resolution results, it is found that the Adams method has the smallest computational error of 1.2 × 10 − 11 compared with the fourth-order Runge–Kutta method and the Richardson extrapolation method. The Adams method is the most computationally efficient in terms of computational time cost, followed by the Richardson extrapolation method, and finally the fourth-order Runge–Kutta method. The results show that the Adams method is the fastest and most accurate for different step sizes and grid volumes.
Supersonic cooling film can reduce the influence of aerodynamic heating to a certain extent, but the complex flow field structure formed by its interaction with the mainstream will cause imaging target offset, ambiguity and jitter, that is, aero-optical effect. In this paper, the variation of cooling efficiency and aero-optical effect at the optical window under different jet States is studied numerically, and the validity of the numerical method is verified by comparing the experimental results. The results show that the cooling efficiency at the optical window is higher and the aero-optical effect is smaller because of the proper total temperature of the cooling jet; The higher the supply pressure of cooling gas, the better the cooling efficiency of film cooling. In order to ensure the weakest aero-optical effect, the cooling gas supply is in pressure matching state; With the increase of Mach number of cooling gas injection, the cooling efficiency and aero-optical effect of supersonic film cooling increase; In general, nitrogen or air is chosen as cooling gas.
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