Aeroacoustics of High Fidelity URANS Simulations of Distributed Electric Propellers

A distributed propeller configuration was investigated by using CFD flow field data and evaluating the acoustics in the far field with the Ffowcs Williams-Hawkings approach. The noise sources were localized by implementing two permeable surfaces within the CFD simulation as input for the acoustic formulation. It can be shown that solely obtaining the propeller noise is not sufficient. Since three propellers are present, the propeller-wing interaction noise has a great impact on the overall noise emission. To reduce the noise, the propellers were vertically shifted, which led to a reduction in propeller-wing interaction noise and an overall noise reduction of 2.4 dB in sound power level. Finally, an extensive parameter study was carried out, showed that propeller distance/phase and direction of rotation, had only minor influence on the overall noise emission.