Towards energy-efficient cooperative flight: A numerical study of V-formation aerodynamics in MALE UAV swarms

Fixed-wing unmanned aerial vehicles (UAVs) are increasingly deployed in civil and military applications, where limited onboard energy constrains endurance and operational sustainability. Cooperative swarm operations offer opportunities to mitigate these constraints by exploiting formation flight to reduce induced drag and power consumption. This study quantifies these benefits for a Bayraktar TB2-class medium-altitude, long-endurance (MALE) UAV in a three-aircraft V-formation. A simplified TB2 geometry, retaining the main lifting surfaces and overall platform, is analyzed using a validated CFD simulation at MALE cruise Reynolds numbers. The formation is parameterized by non-dimensional streamwise, lateral, and vertical offsets, and a structured design of experiments is conducted across lateral and vertical spacings at a fixed streamwise separation, at two representative cruise speeds, and at angles of attack up to 4°. The numerical setup is verified for grid independence and validated in the pre-stall regime against high Reynolds number NASA experimental data for a NACA 4412 wing. Results show that, for suitable spacings, the trailing aircraft’s lift-to-drag ratio increases by 20.07–25.92% at α = 0°–2° and up to 39.18% at α = 4°. The corresponding drag reductions range from 9 to 14% at lower incidence to 20–22% at α = 4°. The most beneficial positions fall in a near-tip inboard band, Δy/b≈−0.075 to −0.0375, with optimal Δz/b = 0 for α = 0° and 2° and Δz/b = 0.125 for α = 4°. These maps provide platform-specific guidance for energy-efficient swarm formations.