Aerodynamic optimization of an externally tilted hex-rotor hovering unmanned aerial vehicle

We investigate the aerodynamic performance and flow field synergy of an externally tilted hex-rotor unmanned aerial vehicle (UAV) in hovering mode, aiming to enhance its hovering efficiency through tailored flow interactions. Experimental measurements and computational fluid dynamics (CFD) simulations are combined to examine the effects of rotor spacing ratio ( i =0.50–0.83) and tilt angle ( θ =0°–40°) on thrust, power consumption, figure of merit (FM), and power loading (PL), with particular emphasis on the underlying aerodynamic coupling mechanisms. The results demonstrate that the optimal configuration ( i =0.56, θ =24°) achieves a 5.43% thrust increase, a 2.73% power reduction, an 11.15% improvement in FM, and a 3.77% enhancement in PL compared to a conventional planar configuration. Flow field analyses reveal that moderate tilting ( θ =24°) promotes downwash convergence and strengthens vortex coupling, thereby increasing the effective flow velocity while minimizing the inter-rotor turbulent interference. Furthermore, the spacing ratio of i =0.56 effectively balances the reduction of detrimental flow interference with the promotion of beneficial flow interactions, as evidenced by stabilized primary vortex structures and constrained recirculation zones in the CFD simulations. This work highlights how the aerodynamic optimization of non-planar rotor configurations is critically dependent on the synergistic control of tilt-induced flow deflection and spacing-dependent interference, and establishes a theoretical framework for understanding multi-rotor flow dynamics; as such, the findings may aid the design of efficient rotor systems for UAVs.