Multi-rotor wake interactions are very complex in nature, especially for small size rotors relevant to UAVs. At small scales, viscous effects dominate the flow field and affect the nature and scale of wake features such as tip vortex and trailing edge vortex sheet. The influence of these wake features on the flow is found to be more spread spatially (with respect to the rotor dimensions) compared to large size helicopter rotors. This hints towards the possibility of affecting the performance of a small multirotor vehicle by deliberate and controlled vortex-blade, vortex-vortex interactions.

Flow induced on a blade by a vortex can cause flow separation or reattachment, strengthening or weakening of tip vortices, or significant change in inflow at blade sections. All of these have implications on aerodynamic efficiency, vibrations, noise, and flight envelop.

In this study, the rotors are synchronized for gaining full control over the wake-wake and blade-wake interactions. The project involves performance and acoustic measurements, flow visualization, and particle image velocimetry.