Aeroacoustics Investigation of Propeller Leading Edge Tubercles Applied to Advanced Air Mobility

Abstract

The application of protuberances on the leading edge of propeller blades for Advanced Air Mobility is another geometrical modification inspired by nature that aims to reduce the noise emissions while maintaining the desired aerodynamic performance. The objective of this paper is to investigate the influence of the shape and size parameters of these tubercles, namely amplitude, wavelength and radial span. Several combinations of those parameters are assessed aerodynamically and acoustically via computational simulations using PowerFLOW, a solver based on the Lattice-Boltzmann method, and the Ffowcs Williams-Hawkings analogy for noise computations in the far-field. Moreover, for several geometrically modified blades, an operational study is conducted to investigate their acoustic behaviour not only for hovering but also for climbing at different rotational velocities. This research is concluded by analysing nature inspired geometries as seen on the fins of humpback whales. The application of tubercles on the leading-edge resulted in an increase of the thrust to torque coefficients ratio of up to 3.3%, while thrust values remained nearly constant and no significant variation in noise emission was identified.