Flow visualizations on a propeller with co-rotating shroud for MAV applications

Stationary shrouds are placed around propellers in many aeronautics applications to improve thrust efficiency, reduce noise, and provide protection from debris. However, their installation requires additional support structures and tight tolerances for blade-tip clearance. For small-scale aerial vehicles, it may be feasible to eliminate these drawbacks by attaching the shroud directly to the blade tips such that they rotate together. We experimentally investigate the potential benefits of such a design, dubbed "prop-shroud", under hover conditions. Various prop-shroud prototypes based on standard NACA airfoil cross-sections are 3D printed to explore the effect of blade and shroud geometry on performance. Particle image velocimetry on select configurations provides insight into the interesting vortex dynamics and changes in the flow field that arise from the addition of a rotating shroud. The observed flow features are interpreted with measurements of thrust, torque, and noise level.