Micro-Rotorcraft Performance Improvement Using Trailing-Edge Gurney Flaps

The improvement in aerodynamic efficiency of micro-scale rotors using miniaturized trailing-edge Gurney flaps is investigated using numerical simulations and experiments. The objective is to use Gurney flaps to enhance the lift and increase the envelope of operation of small-scale airfoils operating at the low Reynolds numbers and Mach numbers that are typical of micro-rotorcraft. Numerical simulations and parametric studies are conducted using a Navier-Stokes flow solver to determine the optimal sizing and location of the micro-scale Gurney flap. The results indicate that the optimal range for the micro-scale Gurney flap geometry is 2-4 % chord length, 0.1-1% chord thickness, and placement at the trailing-edge. Small-scale model tests conducted using a 15-cm diameter micro-rotor system confirmed the validity of the predictions. Addition of the Gurney flap resulted in significant improvement (50 to 75 %) in the micro-rotor thrust, while associated drag increases remained small (25 to 30 %) by comparison. These results indicate that miniaturized Gurney flaps show strong potential to increase the aerodynamic efficiency of micro-flight-vehicles, with minimal increase in complexity, system weight or power penalty.