Abstract

A Mach-scaled slowed rotor was tested at high advance ratios and time-resolved particle image velocimetry was used to characterize the flow field around a blade element in the reverse flow region. Four dominant flow structures were observed: the reverse flow starting vortex, the blunt trailing edge wake sheet, the reverse flow dynamic stall vortex, and the tip vortex. As advance ratio increases, the duration of reduced time that the blade element spends in the reverse flow region also increases. This affects the strength, trajectory, and predicted vortex-induced pitching moment of the reverse flow dynamic stall vortex. The results of this characterization and sensitivity study are compared to canonical models of flow reversal and separation. The three-dimensional rotor flows are found to have many similarities to canonical two-dimensional models.