Aerodynamic Performance Characterization of Leading Edge Protrusions on Small Propellers

Abstract

The relatively large tubercles or protruding bumps on the leading edge of the humpback whale fin create counter-rotating chordwise vortices. At high Reynolds numbers, these vortices have been shown to delay stall with minimal effect on drag. The range of Reynolds numbers that these types of vortices form is unknown, and so an investigation of the potential for an increased envelope of operation for small aircraft propellers was done. For the cases tested in this report no benefits were observed. The addition of leading edge protrusions decreased propeller performance in both efficiency and thrust. Because of the inherent restrictions on propeller chord length and wind speeds due to rotational speed, which in turn limits the Reynolds number, it is unlikely that the type of modification tested in this report will be beneficial for small aircraft propellers typical of unmanned aerial vehicles.