Aeroelastic behavior of a rotating semi-elastic double-swept rotor blade under climb conditions at the Rotor Test Facility Gottingen

Abstract

The study presents the aeroelastic behavior of a double-swept rotor blade, that was investigated under climb conditions on a four-bladed rotor in the rotor test facility at the German Aerospace Center in Gottingen. The results of two ¨ measurement campaigns are combined to obtain a detailed insight in the coupling of blade deformation, integral loads, aerodynamic behavior and blade tip vortex. Especially the interaction between stall onset and blade tip vortex is in focus of the investigation. The first measurement campaign considered the underlying aerodynamics, integral blade loads and blade deformation by means of unsteady pressure-sensitive paint (iPSP), strain gauges at the blade root and blade tip marker. The blade tip vortex behavior was characterized in a second measurement campaign with particle image velocimetry (PIV). Different pitch settings were investigated at a rotation frequency of f rot = 23.6 Hz, that corresponds to blade tip Mach and Reynolds numbers of Mtip = 0.282 - 0.285 and Retip = 5.84 - 5.95 x 105. The results reveal a detailed insight into a two-step stall behavior and its impact on blade flapping and torsion. The iPSP and PIV data indicates an interaction between stall onset at the blade tip and a simultaneous inward motion of the blade tip vortex caused by the backward-swept part of the blade.