Influence of Torque Ratio on Counter-Rotating Open-Rotor Interaction Noise

This paper investigates the influence of the torque ratio, at constant total thrust, on the interaction noise of a generic counter-rotating open rotor in pusher configuration. It is shown that torque ratio has a small influence on the open-rotor aerodynamic performance but a strong impact on interaction noise at takeoff condition. The noise source mechanisms are investigated in detail and linked with the characteristics of the front rotor blade-tip vortices. Tip vortex characteristics are detailed and compared with analytical vortex models. It is verified that torque ratio variation has no strong impact on the open-rotor aerodynamic performance at cruise condition.