Experimental Whirl Tower Tests Approaching and Surpassing Stall for a Variety of Tip Speeds and Rotor Blades

This paper outlines the investigation into the effect of static stall onset in hover on the deformation of rotor blades, comparing the behaviour of a stiff blade featuring a NACA0012 aerofoil, rectangular planform and no taper, and a hingeless blade attachment; with a more flexible blade featuring a NACA23012 aerofoil, twist and taper, and a leadlag hinge. The Munich Experimental Rotor Investigation Testbed (MERIT) at the Technical University of Munich (TUM) was operated in a two-blade configuration at a variety of rotational speeds and collective pitch angles, paired with a stereooptic high speed photogrammetry system. The post-processing methodology used to extract flap and torsional deformations despite the presence of a hinge is outlined, and it was shown that the hinge affected the onset of flow separation and subsequent deformations. A comprehensive set of experimental deformation data for a repeatable setup has been generated and published.