Hybrid CFD-CAA Numerical Simulation of Rotor-Stator Interaction Tonal Noise

In this paper an industrially well suited numerical simulation is performed with the goal of predicting the aerodynamically generated noise at discrete frequencies arising from rotor-stator interaction for a ducted fan configuration. A Frequency based Non-Linear Harmonic (NLH) method is used to predict pressure perturbations on surface of stator vanes, and propagation of these noise signatures in near field. This approach has potential to take into account the acoustic waves propagation across the shear layers as well as inside of boundary layer. A non-reflective boundary condition is applied in order to ensure the continuity across rotor-stator interface along with reconstruction of higher order harmonics on both sides of interface. A Boundary Element Method (BEM) with convective Helmholtz equation and Green's function solution is used to simulate far field sound radiations. The capability of this approach is verified by applying on low mach number NASA Advanced Noise Control Fan. The method works in frequency domain, thus requires only a single passage to be meshed to simulate sound generation and propagation. Results are compared with experimental data and good agreement is achieved at low frequencies with only error at zero degree microphone which is receiving plane waves with azimuthal order zero and relatively acceeptable at third Harmonic.