Wind tunnel testing of a Mach-scaled rotor model with trailing-edge flaps

This paper presents the wind tunnel testing of a four-bladed Mach-scaled rotor model with piezoelectric bender actuated trailing-edge flaps. Correctly phased, this flap motion can be used for the active suppression of vibratory hub loads. First, the University of Maryland Advanced Rotorcraft Code was used to conduct a parametric study to determine the optimal flap sizing and location as well as the required deflection amplitudes. Next, a simplified rotor analysis which explicitly models the actuator dynamics was used to design a multi-layer actuator configuration that is capable of achieving the required flap deflections. Based on the above design studies, a matched set of four Mach-scaled rotor blades with piezo-bender actuated trailing-edge flaps were fabricated in-house. This rotor model was operated using a one-seventh scale Bell-412 Mach-scaled rotor hub. Finally, the rotor system was tested in forward flight in the Glenn L Martin wind tunnel. These tests consisted of open-loop single-frequency tests at different rotor speeds and collective settings. Some preliminary closed-loop tests using a neural network control algorithm were also conducted.