Aerodynamic modeling of coaxial counter-rotating UAV propellers

While coaxial rotor systems experience complex aerodynamic effects, an application to eVTOL UAV can entail positive consequences for the overall system. Aerodynamic calculation of coaxial counter-rotating rotors is carried out and the knowledge gained is used to analyze a wingtip pusher propeller configuration. The aerodynamical model based on the BEMT is adapted to the use cases presented and includes azimuthal inflow and induced velocity components as well as the Prandtl tip loss factor. Wake contraction is calculated using an empirical model for the tip vortex. Moments acting on the rotor hub and oblique inflow can be considered by the discretization of the rotors at arbitrary azimuthal positions. Subsequently, the methods were validated against measurement data from literature and were found in good accordance. Based on aerodynamic parameters, the implemented methods and configurations can be used for rotor and propeller design and modifications.