Aerodynamic and aeroacoustic investigation of swirl recovery vanes for propeller propulsion systems

Swirl recovery vanes (SRVs) are effective in increasing the propulsive efficiency of propeller propulsion systems. Due to the highly periodic flow in the propeller slipstream, unsteady phenomena emerge on the vanes. As the design process omits these phenomena, this manuscript quantifies their relevance and their effect on the far-field noise. Simulations with a lattice-Boltzmann method have been carried out for the aerodynamic flow field, while the far-field noise is computed using the Ffowcs Williams-Hawkings integral solution. The impingement of the propeller blade wake and of the propeller tip vortices on the vanes cause peaks in the thrust generated by the vanes. It is found that the installation of the SRVs causes tonal noise at harmonics of the blade passage frequency, which increases the overall sound pressure both in the upstream and downstream directions. The first harmonic produced by the propeller blades is found to be dominant in the region of maximum noise where the vanes have a minimal contribution.