11th European Conference on Turbomachinery Fluid dynamics & Thermodynamics
An innovative technique is presented to reduce noise from turbofan aircraft engines by incorporating the acoustic treatment with liners in engine ducts. The tonal noise source and the near field sound propagation in the nacelle duct are simultaneously predicted with a single CFD analysis based on an efficient Nonlinear Harmonic (NLH) method. The wall acoustic impedance has been incorporated in the NLH module of the solver and effectively damps the acoustic pressure fluctuations by a factor corresponding to the measured impedance. The sound radiation to the far field is computed with the Greens function approach implemented in a Boundary Element Method (BEM) frequency domain solver of the convective Helmholtz equation. The approach has been validated through various test cases, including a comparison with experimental results from the Grazing Incidence Tube at the NASA Langley Research Center. This approach has also been applied to the simulation of the ANCF (Advanced Noise Control Fan) engine developed at the NASA Glenn Research Center for the cases with and without liner.