Aeroacoustic modeling of helicopter transonic rotor noise

The noise propagation of an helicopter rotor with blade tip in transonic regime is numerically simulated. To calculate the acoustic characteristics of the helicopter rotor, a novel CFD/Penetrable Surface Ffowcs Williams-Hawkings (PS-FWH) hybrid approach is established. The approach is characterized by the solution of the Reynolds-Averaged Navier-Stokes (RANS) equations on a Chimera system of overset meshes, coupled with an in-house acoustic code (ROCAAP), which employs the PS-FWH method with a Marching-Cube Emission-Surface (MCES) integral algorithm, for the noise propagation. The hybrid approach is validated through two databases. The well-known Caradonna-Tung hovering rotor test is used to assess the pressure distribution at each cross-section along the blade. The transonic acoustic survey of the UH-1H rotor is adopted to evaluate the time domain noise signal with different blade tip Mach numbers during hover. The capabilities of the hybrid method to predict helicopter transonic rotor noise are demonstrated through the achieved good correlation with experimental data.