A Parametric Investigation of Rotor-Rotor Interaction Noise Generation

An extensive parametric study of a two rotor system configurations is conducted to investigate the effect of rotor placement on noise generation, with the aim of providing preliminary design information to multirotor aircraft designers. A computationally efficient wake method called OpenCOPTER is used to conduct the aerodynamic simulations and PSU-WOPWOP is used to predict the rotor sound power level over an acoustic hemisphere. An extensive parameter sweep is explored consisting of several different rotor placements and operating conditions. Aerodynamic interactions between the rotors are found to result in significant rotor-rotor interaction noise when the downstream rotor is placed in two different regions behind the upstream rotor. The rotor-rotor interaction noise also varies as the rotors are offset laterally. Even for conditions where rotor-rotor interaction noise does not occur, aerodynamic interactions between the rotors can affect how rotors interact with their own wake. Positioning the downstream rotor above, but relatively close to, the upstream rotor is shown to result in a robust reduction in noise across the entire operating envelope.