Abstract:
Presented herein is a comprehensive workflow for the aeroacoustic analysis of a tilt-rotor air taxi during cruise and hover flight using high-fidelity numerical methods. Employing a hybrid approach, the near-field flow is resolved by an unsteady Reynolds-Averaged Navier-Stokes (URANS) solver, which is paired with a Ffowcs Williams-Hawkings (FW-H) acoustic solver to compute the far-field noise. Both impermeable and permeable FW-H integration surface approaches are incorporated. To balance computational resources and accuracy, the flow domain is halved, while the acoustic data is processed to reflect the full vehicle acoustics. Isolated acoustic contributions of each rotor are extracted, allowing the investigation into the impact of phase shifts on the acoustic signature of the vehicle. Spectral analysis, directivity maps, and noise hemispheres reveal the resolution of fundamental open rotor characteristics and amplified tonal interaction noise that can be linked to aeropropulsive phenomena. The introduction of phase shifts can lead to reduced noise levels and an unsymmetrical acoustic field development. A direct comparison of the results based on impermeable and permeable FW-H source surfaces shows general agreement on the directivity prediction but significant differences in noise levels, potentially due to numerical dissipation, grid settings and the symmetry boundary.