Drag reduction on multi-bump technology based on free-form deformation method for flying wing unmanned aerial vehicle coupled with intake and exhaust system

In order to further improve the aerodynamic performance of flying wing UAV coupled with intake and exhaust system, research on drag reduction characteristics and optimization design of the multi-bump near the wing surface of intake and exhaust system was taken. Firstly, the FFD(Free-Form Deformation) method based on the elastomeric theory was introduced. It was effective for geometry parameterization of multi-bump, and it also provided an efficient way to generate the three-dimensional flow field grid automatically. Then combined with the γ-Re_θt transition model, numerical simulation was implemented. Finally, the RBF surrogate model and Multi-Island genetic algorithm were adopted to take an optimization on the multi-bump parameters. Results indicated that the multi-bump technology based on FFD adopts less design variable but has higher optimization efficiency. The optimized model suggests that the first bump is hollow, and the latter two bumps are convex. And it has remarkable drag reduction effect and the total drag reduction can reach about 6.2% at attack angle of 6°. With the attack angle increasing, the drag reduction influenced mainly by the friction drag leads to pressure dominated drag reduction.