Broadband noise due to rotor-wake/rotor interaction in contra-rotating open rotors

A semi-analytical model for the prediction of the broadband noise due to the interaction between turbulent rotor wakes and a rotor in contra-rotating open rotors is presented. The unsteady loading of the rear rotor is modeled using classical isolated flat-plate theory. Strip theory is used to treat the spanwise variations of aerodynamic quantities and blade geometry. The turbulent wake is assumed to be homogeneous and isotropic turbulence that is modulated by a train of wake profiles. The model is presented in detail and insight into its modal behavior is provided. A parameter study is conducted to investigate the effects of blade number, rotor–rotor gap and rotor speeds on broadband noise emissions due to rotor–wake/rotor interaction in contra-rotating open rotors. Scaling laws for sound power levels have been established analytically and show good agreement with the results of the parameter stud