Investigation of the Combined Application of Leading-Edge Tubercles and Trailing-Edge Serration on AAM Propellers in Terms of Aeroacoustics Using Lattice-Boltzmann Method

Abstract

The individual geometrical modifications of a propeller blade geometry on the leading-edge (tubercles) as well as on the trailing-edge (serration), which have already been investigated in numerous publications, are applied in combination in this work. Results for those propellers, which can be mounted to advanced air mobility vehicles, are obtained using computational simulations which are based on the Lattice Boltzmann Method. This study not only focuses on analyzing the aerodynamic performance parameters as well as the acoustic output data in comparison to the unmodified blade geometry, moreover, the mechanisms that lead to changes in those parameters are investigated. The operational conditions influence the acoustic results, particularly changes in the broadband noise levels are observed. To investigate the source of the acoustic level increases of up to 15 dB for higher frequencies, the development of both the streamlines and the turbulent kinetic energy are examined. The results indicate that laminar separation bubbles are a potential contributory factor to the increase in acoustic output. Although the geometrical modifications cannot prevent their formation, significantly higher thrust to torque efficiencies, mainly based on the reduction of the required power input, can be achieved while maintaining similar noise emissions as the unmodified reference blade.