Noise Prediction of an Open Fan Using Acoustic Analogy Approaches

The purpose of this study is to evaluate numerical aero-acoustic methods for the noise prediction of an open fan, which is expected to reduce CO2 emissions for the next generation of aircraft engines. The far-field noise is computed using a CFD/CAA approach. The unsteady Reynolds Averaged Navier-Stokes (uRANS) and the Ffowcs Williams-Hawkings (FWH) analogy using solid and permeable surfaces are applied. The phase-lag method (single-blade passage) is used for the purpose of calculation for aerodynamic flow and noise sources with ONERA elsA finite volume solver. The sensitivities to the numerical CFD setup as well as the position and formulation of FWH permeable surface for noise computation are discussed in this paper. The present noise prediction strategy is evaluated for approach and take-off operating conditions. In particular, several spatial discretization schemes and FWH surface locations are tested and compared to evaluate their influence on the noise levels and directivity.