Analytical tool development for sound directivity simulation and control in a multicopter configuration

This thesis explores the development of fast simulation software for predicting the sound directivity of multirotor aircraft in hover. The software utilizes simplified analytical formulations derived from the Ffowcs-Williams-Hawkings (FW-H) aeroacoustic equations. A key simplification involves representing each rotor blade's sound emission as a single point source rather than a distributed source. This approach enables rapid predictions of sound directivity for various multirotor configurations and rotor phase shifts. The software is validated against results from a NASA publication and simulations conducted by APSIM (software to predict rotor and propeller noise by DLR). In the final stage of the research, the simulation software is combined with a genetic algorithm to optimize rotor phasing. Rotor phasing refers to the relative timing of each rotor's rotation, which affects the resulting sound field. The objective is to determine the optimal phase relationship between rotors to minimize noise in a specific target direction, such as downward noise toward people or away from sensitive equipment. A genetic algorithm, inspired by the principles of natural selection, is used to explore potential phasing configurations. By using the simulation's rapid predictions, the algorithm efficiently identifies the rotor configuration that achieves the desired noise reduction.