Review of Multi-Rotor Noise Prediction Techniques

View Video Presentation: https://doi.org/10.2514/6.2022-3463.vid An exhaustive review of multi-rotor noise prediction and control methods is presented. A brief history of rotor prediction methods is discussed, some classical rotor theories are revisited. More recent aerodynamic methods such as the viscous vortex particle method and non-linear vortex lattice methods are explored, and their limitations mentioned. The tonal noise for an isolated rotor was found to be a result of the difference in static pressure between the suction side and pressure side of the rotors. These can be predicted using most of the methods discussed. In multi-rotor systems, the proximity of the rotors affects the performance and at the same rotational rate, increases the fundamental tone. The broadband noise is seen to be generated by both the rotor self-noise as well as some contributions of the wake at lower frequencies. The total broadband noise is seen to only be predictable using high-fidelity methods. By using Amiet’s theories, the lower fidelity methods can predict blade self-noise but misses out on the wake effects.