Influence of vertical rotor spacing on aerodynamic efficiency of quadcopter configurations

Kurzfassung

The aerodynamic interactions in a quadcopter during forward flight reduce the efficiency of the back rotor(s) and increase generated noise levels. To alleviate interactions without compromising the vehicle’s compactness, a vertical offset between the front and back rotor(s) can be introduced as an alternative solution to increased hub spacing. The efficiency of a quadcopter in square and diamond configuration with a vertical spacing up to 0.38 rotor diameter is analysed experimentally and numerically using free-wake solvers. Forward flight conditions are considered, including high interaction cases with a nose-up tilt and close rotor hub spacing with overlapping blades. The results show that for the square configuration, a thrust comparable to four isolated rotors is achieved by the elevation of both back rotors. In contrast, introducing a vertical separation to the already underperforming back rotor in the diamond configuration further reduces its efficiency.