Numerical Investigation of the Acoustics Radiation of a Two-Bladed Rotor in Interaction with a Beam

This work investigates the acoustic radiation of a rotor in interaction with a beam at low Reynolds and Mach numbers. Specifically, non-compressible Implicit Large Eddy Simulations in combination with a solid Ffowcs–Williams–Hawkings formulation are performed for a two-bladed rotor in interaction with circular beams of different sizes. The interest in using numerical simulations partly lies in the possibility to locate and quantify the acoustic sources from different parts of the geometry. The comparison between the numerical results and experimental data shows that acoustic levels are in good agreement for frequencies ranging from the Blade Passing Frequency (BPF) to its ninth harmonics. However, the simulations do not solve for the smallest turbulent structures and hence are not able to capture high-frequency broadband noise. The results obtained with and without beam demonstrates that its presence has no effect on the BPF, but it increases the amplitudes of its harmonics. Using only parts of the surfaces for the application of the FWH formulation, the beam is seen to be the main contributor of noise at the BPF harmonics. Finally, the distribution of acoustic sources along the beam is analyzed, and it varies from a quasi-uniform distribution below the blade for the first harmonics to a none-uniform distribution with maximal value below the blade tip for harmonics with higher orders.