Mechanical concept of aeroelastic demonstrator and methodology for experimental investigation of propeller aerodynamic derivatives

Abstract

: Whirl flutter is a specific type of flutter instability, for which the experimental validation of the analytical results is required. One of the key issues is the solution of propeller aerodynamic forces on a vibrating propeller. To determine propeller forces and moments, aerodynamic derivatives are used. The complete solution includes six independent derivatives, four of which may be investigated experimentally. The subjected demonstrator represents a sting-mounted nacelle with a motor and propeller. It includes engine pitch and yaw degrees-of-freedom. Both stiffness constants are adjustable and both pivots are movable in the direction of the propeller axis. For the measurement, a single degree-of-freedom model is to be used; therefore, the blocking of either pitch or yaw movement is provided. Pitching moment (c m  ) and vertical force (c z  ) due to the pitch angle derivatives will be measured using pitch-only model arrangement. Pitching moment (c m  ) and vertical force (c z  ) due to the yaw angle derivatives will be measured using yaw-only model arrangement. Measurement includes pitch and yaw angles and pitch or yaw pivot moment, respectively. To separate the contributions of both force and moment to the total moment, the measurement of two configurations varying the distance between the gimbal axis and the propeller plane is used.