Computational investigation of micro rotorcraft near-wall hovering aerodynamics

Micro rotorcraft are considered a promising unmanned aerial platform owing to their high manoeuvrability and small footprint, which together allow for operation within very confined environments. This paper presents a computational investigation into a key challenge that limits micro rotorcraft performance within confined environments: Disturbance phenomena that occur due to aerodynamic interactions between rotors and nearby walls. The results of this study show that a micro rotor hovering near a wall will experience two wake asymmetry phenomena: Asymmetry in wake shape and asymmetry in vortex circulation strength. These asymmetry phenomena induce additional rotor force components that vary with rotor azimuthal angle. When averaged over time, these forces generate moments that present a disturbance large enough to have a significant adverse effect on micro rotorcraft blade flapping and attitude dynamics. Ultimately, this places the rotorcraft at a high risk of collision with the wall. This key result is fundamental to future design of disturbance observers and control systems that will be essential for future development of reliable confined environment micro rotorcraft systems.