Effects of rotor-rotor and rotor-body interactions on quadrotor vehicle performance for multiple flight configurations

Rotor-rotor and rotor-body interactions can have a first-order influence on multirotor vehicle performance throughout its flight envelope and are highly dependent on flight speed and attitude. Characterizing these performance impacts has previously been limited to either computational methods or experimental testing in controlled environments, and has yet to be extended to a free-flying, full-scale vehicle. This work presents a series of flight tests and equivalent-trim-condition wind tunnel experiments of a quadrotor vehicle at multiple speeds and sideslip (skew) angles to investigate rotor-rotor and rotor-body interactions. Performance data, quantified by thrust coefficient, was measured for individual rotors at flight speeds from 7 to 15 m/s over an extensive range of vehicle skew angles. Wind tunnel experiments with and without the flight test vehicle fuselage revealed a 7.7% thrust coefficient penalty for the aft rotor in the plus ( +) configuration when the fuselage was present. In both wind tunnel and flight tests, the plus configuration showed a higher overall thrust coefficient. In flight test, electrical power measurements further showed decreased power requirements in the plus compared to the cross (x) configuration, despite generating increased drag. The optimum flight condition was found to be at 10 m/s in the plus configuration. The rotor rotational direction (clockwise or counterclockwise) coupled with vehicle orientation had a substantial impact on the resulting rotor thrust coefficients. In the cross configuration, higher thrust coefficient and lower power consumption were observed when the advancing side of the rotor blade was outboard compared to inboard. Through both wind tunnel and flight tests, trends in rotor performance at skew angles between the cross and plus configurations were found to be asymmetric with respect to both skew angle and vehicle flight velocity.