Numerical simulation of power and flow field characteristics of conformal intake and exhaust for flying wing unmanned aerial vehicle

Using computational fluid dynamics (CFD) method, we performed numerical simulations on the wind tunnel test model of conformal inlet and expansion nozzle; they were aimed at verifying the reliability of the boundary conditions on power simulation. Keeping in mind the stealth and conformal requirements of twin-engine flying wing UAV, we designed a S-shaped inlet with rectangular intake and a circular-rectangle nozzle. And then numerical simulation was carried out on the intake and exhaust system, and it was also applied to studying the aerodynamic performance of UAV and three-dimensional flow field characteristics of the intake and exhaust. Results and their analysis indicate: (1) the lift/drag characteristic of flying wing UAV declines when adopting the intake and exhaust, but it can be used to improve the longitudinal moment characteristic under the low Mach number 0.5 and 0.6; (2) with increasing Mach number, the total pressure recovery coefficient decreases and the distortion coefficient increases, while the axial thrust coefficient increases and the thrust performance remains relatively satisfactory; the inlet performance decreases rapidly at the high Mach number 0.7; so we should pay more attention to the right border of the flight envelope in the design; (3) the sideslip angle exerts greater influence on the inlet performance, while the thrust performance of nozzle is less affected; so we also should pay more attention to the impact of sideslip angle on inlet.