Hover Performance And Boundary Layer Measurements Of Low Reynolds Number Rotors

Abstract

Two teams optimized low Reynolds number rotors with the goal of improving hover and loiter performance of a small commercial off the shelf quadrotor unmanned aerial system. The resulting rotors were constructed and tested against the baseline system hover. The optimized rotors achieved 6% and 3% increases in figure of merit at the design 1.5 lbf thrust in hover, while carefully chosen boundary layer trips improved low RPM performance of one optimized rotor. IR thermography identified the qualitative location and extent of laminar separation bubbles and turbulent transition on the upper rotor surface. The IR images reveal large differences in the boundary layer structure between the baseline and two optimized rotors, with separation and reattachment occurring further forward and over a smaller chordwise extent in the optimized rotors. After optimization, a mid-fidelity lifting line coupled vortex particle code and high-fidelity Helios CFD code were used to simulate the baseline and one optimized rotor system.