Abstract: Motivated by optimal combination of paired wings configuration and stroke-plane inclination in biological flapping flights that can achieve high aerodynamic performance, we propose a biomimetic rotor-configuration design to explore optimal aerodynamic performance in multirotor drones. While aerodynamic interactions among propellers in multirotor Unmanned Aerial Vehicles (UAVs) play a crucial role in lift force production and Figure of Merit (FM) efficiency, the rotor-configuration effect remains poorly understood. Here we address a Computational Fluid Dynamics (CFD)-based study on optimal aerodynamic performance of the rotor-configuration in hovering quadrotor drones with a specific focus on the aerodynamic effects of tip distance, height difference and tilt angle of propellers. Our results indicate that the tip distance-induced interactions can most alter lift force production and hence lead to remarked improvement in FM, and the height difference also plays a key role in improving aerodynamic performance, while the tilt angle effect is less important. Furthermore, we carried out an extensive analysis to explore the optimal aerodynamic performance of the rotor-configuration over a broad parameter space, by combining the CFD-based simulations and a novel surrogate model. We find that a rotor-configuration with a large tip distance and some height difference with zero tilt angle is capable of optimizing both lift force production and FM, which could offer a novel optimal design as well as maneuver strategy for multirotor UAVs.

Key words: bioinspiration, optimal quadrotor configuration, aerodynamic interactions, aerodynamic performance, CFD, surrogate modeling