Tonal Noise Emission of an Elastic Propeller in Hover Using a Mid-Fidelity Approach

Propeller blades are usually made from lightweight materials and have long, slender designs. Thus, their natural vibrations and deformations can substantially affect both their aerodynamic performance and acoustic footprint. In this work, a mid-fidelity solver is used to investigate the impact of blade deformability on tonal noise emission of small propellers operating at low Reynolds numbers. Specifically, the acoustic pressure perturbation perceived by farfield observers is computed by solving a Ffowcs Williams-Hawkings integral formulation. To capture the aeroelastic effects, an open-source two-way partitioned Fluid-Structure Interaction framework is used. This involves the coupling of the multi-body dynamics solver MBDyn with the mid-fidelity vortex-lattice aerodynamics solver in DUST via the preCICE mapping library. The spectral analysis of provided noise measurements for a small-scale, two-blade propeller reveals additional peaks between the blade passing frequencies. These peaks are numerically investigated in this study and are further elucidated by considering the blade flexibility.