An approach for formation design and flight performance prediction based on aerodynamic formation unit: Energy-saving considerations

The performance improvement of swarm drones through aerodynamic shape optimization may be challenging due to folded size constraints imposed by the specific launch approach. However, fixed-wing aircraft swarms can benefit from formation flight in terms of energy consumption. This study introduces the concept of the “aerodynamic formation unit”, which consists of two or three aircraft that form an inseparable unit of the formation. Considering the Unmanned Aerial Vehicle (UAV) distribution and wingtip vortex interference in the formation, two typical aerodynamic formation units are optimized by the variable-fidelity aerodynamic optimization method based on space mapping. The aerodynamic characteristics of the formation UAVs that affect flight performance, such as lift-to-drag ratio (L/D ratio) and static stability are analyzed by Computational Fluid Dynamics (CFD) simulations. The L/D ratio (cruising condition) of the following aircraft can be increased by 22.8% and 57.5% in the optimal units that involve two and three aircraft respectively. Moreover, this study conducts several CFD simulations for multi-aircraft formations formed by the units, which show that the average L/D ratio of the formation can be improved by more than 19%. These results verify the feasibility and effectiveness of the “aerodynamic formation unit” concept and the optimization framework for formation parameters.