A numerical study of the duct geometry effects on the aerodynamics and aeroacoustics of ducted propellers

Ducted propellers show large applicability in urban air mobility applications due to their operational safety, increased aerodynamic performance and noise reduction potential. In this work, we study the effect of the duct's lip design on the aerodynamics and aeroacoustics of ducted propellers in hover with numerical simulations, which are validated with experiments. Steady numerical simulations were conducted first to efficiently evaluate the impact of the lip design on the aerodynamic performance. The results show how the design of the lip affects the uniformity of the incoming flow to the propeller and the pressure distribution on the duct. Based on these results, an improved lip geometry is proposed, whose noise generation is investigated with delayed detached eddy simulations and the noise radiation to the far field is computed using the integral solution of the Ffowcs-Williams and Hawkings equation. The experimental results show reasonable agreement regarding thrust generation and far-field noise. The spectrum and directivity of the aerodynamic noise are compared, and the primary noise sources are identified in the leading edge and tip of the propeller.