Conformal asymmetry S-shaped inlet design and optimization of flying wing unmanned aerial vehicle

Based on domestic power constraint and stealth design requirements, conformal S-shaped inlet was designed for twin-engine flying wing unmanned aerial vehicle. In order to further improve the inlet performance, the optimization research on the inlet design was carried out. First, a verification on the wind tunnel test model of conformal inlet was made by CFD (computational fluid dynamics). And then CFD numerical simulation was carried out combining with parametric modeling and automatic mesh generation technique. Finally, RBF (radial basis function neural network) surrogate model and multi-island genetic algorithm were used to take an optimization on the inlet parameters. Results indicated: (1)The aerodynamic performance of optimized inlet improved, and especially it improves significantly after the attack angle of 4°. The total pressure recovery coefficient increased by 5.46%,and the distortion coefficient decreased by 38.7% at the Mach number of 0.6 and attack angle of 4°. (2)Compared to the initial configuration, the area distribution of optimized inlet changed gently in the front but increases slightly behind; while the centerline of former 1/3 was consistent with the initial configuration, and after that the curvature changed more smoothly. (3) The conformal inlet has strong secondary flow at the exit. The sideslip angle made a little influence on the inlet performance under small attack angle but it had greater influence at large attack angle. So the sideslip performance under large attack angle should be paid more attention.