Small-Scale Propellers Operating in the Vortex Ring State

The behavior of small-scale propellers operating in vertical descent and through the vortex ring state (VRS) was measured. In particular, a total of 26 propellers with diameters ranging from 9 to 11 in. (0.229 to 0.279 m) were tested in the University of Illinois at Urbana-Champaign (UIUC) 2.8×4 ft (0.853×1.219 m) low-turbulence wind tunnel at low Reynolds numbers to measure the propeller thrust over a range of advance ratios from −0.8 to 0 (rapid descent to hover). Also, time histories of the measured thrust for different propellers were recorded to characterize the unsteady thrust fluctuations for advance ratios through the vortex ring state. The effects of propeller geometry, e.g. pitch and planform effects, on the thrust characteristics of these propellers in the vortex ring state is discussed.